tccelf.c

/*
 *  ELF file handling for TCC
 *
 *  Copyright (c) 2001-2004 Fabrice Bellard
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include "tcc.h"

/* Define this to get some debug output during relocation processing.  */
#undef DEBUG_RELOC

/********************************************************/
/* global variables */

/* elf version information */
struct sym_version {
    char *lib;
    char *version;
    int out_index;
    int prev_same_lib;
};

#define nb_sym_versions     s1->nb_sym_versions
#define sym_versions        s1->sym_versions
#define nb_sym_to_version   s1->nb_sym_to_version
#define sym_to_version      s1->sym_to_version
#define dt_verneednum       s1->dt_verneednum
#define versym_section      s1->versym_section
#define verneed_section     s1->verneed_section

/* special flag to indicate that the section should not be linked to the other ones */
#define SHF_PRIVATE 0x80000000
/* section is dynsymtab_section */
#define SHF_DYNSYM 0x40000000

#ifdef TCC_TARGET_PE
static const int shf_RELRO = SHF_ALLOC;
static const char rdata[] = ".rdata";
#else
static const int shf_RELRO = SHF_ALLOC | SHF_WRITE;
static const char rdata[] = ".data.ro";
#endif

/* ------------------------------------------------------------------------- */

ST_FUNC void tccelf_new(TCCState *s)
{
    TCCState *s1 = s;
    /* no section zero */
    dynarray_add(&s->sections, &s->nb_sections, NULL);

    /* create standard sections */
    text_section = new_section(s, ".text", SHT_PROGBITS, SHF_ALLOC | SHF_EXECINSTR);
    data_section = new_section(s, ".data", SHT_PROGBITS, SHF_ALLOC | SHF_WRITE);
    /* create ro data section (make ro after relocation done with GNU_RELRO) */
    rodata_section = new_section(s, rdata, SHT_PROGBITS, shf_RELRO);
    bss_section = new_section(s, ".bss", SHT_NOBITS, SHF_ALLOC | SHF_WRITE);
    common_section = new_section(s, ".common", SHT_NOBITS, SHF_PRIVATE);
    common_section->sh_num = SHN_COMMON;

    /* symbols are always generated for linking stage */
    symtab_section = new_symtab(s, ".symtab", SHT_SYMTAB, 0,
                                ".strtab",
                                ".hashtab", SHF_PRIVATE);
    s->symtab = symtab_section;

    /* private symbol table for dynamic symbols */
    s->dynsymtab_section = new_symtab(s, ".dynsymtab", SHT_SYMTAB, SHF_PRIVATE|SHF_DYNSYM,
                                      ".dynstrtab",
                                      ".dynhashtab", SHF_PRIVATE);
    get_sym_attr(s, 0, 1);
}

#ifdef CONFIG_TCC_BCHECK
ST_FUNC void tccelf_bounds_new(TCCState *s)
{
    TCCState *s1 = s;
    /* create bounds sections (make ro after relocation done with GNU_RELRO) */
    bounds_section = new_section(s, ".bounds", SHT_PROGBITS, shf_RELRO);
    lbounds_section = new_section(s, ".lbounds", SHT_PROGBITS, shf_RELRO);
}
#endif

static void free_section(Section *s)
{
    tcc_free(s->data);
}

ST_FUNC void tccelf_delete(TCCState *s1)
{
    int i;

#ifndef ELF_OBJ_ONLY
    /* free symbol versions */
    for (i = 0; i < nb_sym_versions; i++) {
        tcc_free(sym_versions[i].version);
        tcc_free(sym_versions[i].lib);
    }
    tcc_free(sym_versions);
    tcc_free(sym_to_version);
#endif

    /* free all sections */
    for(i = 1; i < s1->nb_sections; i++)
        free_section(s1->sections[i]);
    dynarray_reset(&s1->sections, &s1->nb_sections);

    for(i = 0; i < s1->nb_priv_sections; i++)
        free_section(s1->priv_sections[i]);
    dynarray_reset(&s1->priv_sections, &s1->nb_priv_sections);

    /* free any loaded DLLs */
#ifdef TCC_IS_NATIVE
    for ( i = 0; i < s1->nb_loaded_dlls; i++) {
        DLLReference *ref = s1->loaded_dlls[i];
        if ( ref->handle )
# ifdef _WIN32
            FreeLibrary((HMODULE)ref->handle);
# else
            dlclose(ref->handle);
# endif
    }
#endif
    /* free loaded dlls array */
    dynarray_reset(&s1->loaded_dlls, &s1->nb_loaded_dlls);
    tcc_free(s1->sym_attrs);

    symtab_section = NULL; /* for tccrun.c:rt_printline() */
}

/* save section data state */
ST_FUNC void tccelf_begin_file(TCCState *s1)
{
    Section *s; int i;
    for (i = 1; i < s1->nb_sections; i++) {
        s = s1->sections[i];
        s->sh_offset = s->data_offset;
    }
    /* disable symbol hashing during compilation */
    s = s1->symtab, s->reloc = s->hash, s->hash = NULL;
#if defined TCC_TARGET_X86_64 && defined TCC_TARGET_PE
    s1->uw_sym = 0;
#endif
}

/* At the end of compilation, convert any UNDEF syms to global, and merge
   with previously existing symbols */
ST_FUNC void tccelf_end_file(TCCState *s1)
{
    Section *s = s1->symtab;
    int first_sym, nb_syms, *tr, i;

    first_sym = s->sh_offset / sizeof (ElfSym);
    nb_syms = s->data_offset / sizeof (ElfSym) - first_sym;
    s->data_offset = s->sh_offset;
    s->link->data_offset = s->link->sh_offset;
    s->hash = s->reloc, s->reloc = NULL;
    tr = tcc_mallocz(nb_syms * sizeof *tr);

    for (i = 0; i < nb_syms; ++i) {
        ElfSym *sym = (ElfSym*)s->data + first_sym + i;
        if (sym->st_shndx == SHN_UNDEF
            && ELFW(ST_BIND)(sym->st_info) == STB_LOCAL)
            sym->st_info = ELFW(ST_INFO)(STB_GLOBAL, ELFW(ST_TYPE)(sym->st_info));
        tr[i] = set_elf_sym(s, sym->st_value, sym->st_size, sym->st_info,
            sym->st_other, sym->st_shndx, (char*)s->link->data + sym->st_name);
    }
    /* now update relocations */
    for (i = 1; i < s1->nb_sections; i++) {
        Section *sr = s1->sections[i];
        if (sr->sh_type == SHT_RELX && sr->link == s) {
            ElfW_Rel *rel = (ElfW_Rel*)(sr->data + sr->sh_offset);
            ElfW_Rel *rel_end = (ElfW_Rel*)(sr->data + sr->data_offset);
            for (; rel < rel_end; ++rel) {
                int n = ELFW(R_SYM)(rel->r_info) - first_sym;
                if (n < 0) /* zero sym_index in reloc (can happen with asm) */
                    continue;
                rel->r_info = ELFW(R_INFO)(tr[n], ELFW(R_TYPE)(rel->r_info));
            }
        }
    }
    tcc_free(tr);

    /* record text/data/bss output for -bench info */
    for (i = 0; i < 4; ++i) {
        s = s1->sections[i + 1];
        s1->total_output[i] += s->data_offset - s->sh_offset;
    }
}

ST_FUNC Section *new_section(TCCState *s1, const char *name, int sh_type, int sh_flags)
{
    Section *sec;

    sec = tcc_mallocz(sizeof(Section) + strlen(name));
    sec->s1 = s1;
    strcpy(sec->name, name);
    sec->sh_type = sh_type;
    sec->sh_flags = sh_flags;
    switch(sh_type) {
    case SHT_GNU_versym:
        sec->sh_addralign = 2;
        break;
    case SHT_HASH:
    case SHT_GNU_HASH:
    case SHT_REL:
    case SHT_RELA:
    case SHT_DYNSYM:
    case SHT_SYMTAB:
    case SHT_DYNAMIC:
    case SHT_GNU_verneed:
    case SHT_GNU_verdef:
        sec->sh_addralign = PTR_SIZE;
        break;
    case SHT_STRTAB:
        sec->sh_addralign = 1;
        break;
    default:
        sec->sh_addralign =  PTR_SIZE; /* gcc/pcc default alignment */
        break;
    }

    if (sh_flags & SHF_PRIVATE) {
        dynarray_add(&s1->priv_sections, &s1->nb_priv_sections, sec);
    } else {
        sec->sh_num = s1->nb_sections;
        dynarray_add(&s1->sections, &s1->nb_sections, sec);
    }

    return sec;
}

ST_FUNC Section *new_symtab(TCCState *s1,
                           const char *symtab_name, int sh_type, int sh_flags,
                           const char *strtab_name,
                           const char *hash_name, int hash_sh_flags)
{
    Section *symtab, *strtab, *hash;
    int *ptr, nb_buckets;

    symtab = new_section(s1, symtab_name, sh_type, sh_flags);
    symtab->sh_entsize = sizeof(ElfW(Sym));
    strtab = new_section(s1, strtab_name, SHT_STRTAB, sh_flags);
    put_elf_str(strtab, "");
    symtab->link = strtab;
    put_elf_sym(symtab, 0, 0, 0, 0, 0, NULL);

    nb_buckets = 1;

    hash = new_section(s1, hash_name, SHT_HASH, hash_sh_flags);
    hash->sh_entsize = sizeof(int);
    symtab->hash = hash;
    hash->link = symtab;

    ptr = section_ptr_add(hash, (2 + nb_buckets + 1) * sizeof(int));
    ptr[0] = nb_buckets;
    ptr[1] = 1;
    memset(ptr + 2, 0, (nb_buckets + 1) * sizeof(int));
    return symtab;
}

/* realloc section and set its content to zero */
ST_FUNC void section_realloc(Section *sec, unsigned long new_size)
{
    unsigned long size;
    unsigned char *data;

    size = sec->data_allocated;
    if (size == 0)
        size = 1;
    while (size < new_size)
        size = size * 2;
    data = tcc_realloc(sec->data, size);
    memset(data + sec->data_allocated, 0, size - sec->data_allocated);
    sec->data = data;
    sec->data_allocated = size;
}

/* reserve at least 'size' bytes aligned per 'align' in section
   'sec' from current offset, and return the aligned offset */
ST_FUNC size_t section_add(Section *sec, addr_t size, int align)
{
    size_t offset, offset1;

    offset = (sec->data_offset + align - 1) & -align;
    offset1 = offset + size;
    if (sec->sh_type != SHT_NOBITS && offset1 > sec->data_allocated)
        section_realloc(sec, offset1);
    sec->data_offset = offset1;
    if (align > sec->sh_addralign)
        sec->sh_addralign = align;
    return offset;
}

/* reserve at least 'size' bytes in section 'sec' from
   sec->data_offset. */
ST_FUNC void *section_ptr_add(Section *sec, addr_t size)
{
    size_t offset = section_add(sec, size, 1);
    return sec->data + offset;
}

#ifndef ELF_OBJ_ONLY
/* reserve at least 'size' bytes from section start */
static void section_reserve(Section *sec, unsigned long size)
{
    if (size > sec->data_allocated)
        section_realloc(sec, size);
    if (size > sec->data_offset)
        sec->data_offset = size;
}
#endif

static Section *have_section(TCCState *s1, const char *name)
{
    Section *sec;
    int i;
    for(i = 1; i < s1->nb_sections; i++) {
        sec = s1->sections[i];
        if (!strcmp(name, sec->name))
            return sec;
    }
    return NULL;
}

/* return a reference to a section, and create it if it does not
   exists */
ST_FUNC Section *find_section(TCCState *s1, const char *name)
{
    Section *sec = have_section(s1, name);
    if (sec)
        return sec;
    /* sections are created as PROGBITS */
    return new_section(s1, name, SHT_PROGBITS, SHF_ALLOC);
}

/* ------------------------------------------------------------------------- */

ST_FUNC int put_elf_str(Section *s, const char *sym)
{
    int offset, len;
    char *ptr;

    len = strlen(sym) + 1;
    offset = s->data_offset;
    ptr = section_ptr_add(s, len);
    memmove(ptr, sym, len);
    return offset;
}

/* elf symbol hashing function */
static ElfW(Word) elf_hash(const unsigned char *name)
{
    ElfW(Word) h = 0, g;

    while (*name) {
        h = (h << 4) + *name++;
        g = h & 0xf0000000;
        if (g)
            h ^= g >> 24;
        h &= ~g;
    }
    return h;
}

/* rebuild hash table of section s */
/* NOTE: we do factorize the hash table code to go faster */
static void rebuild_hash(Section *s, unsigned int nb_buckets)
{
    ElfW(Sym) *sym;
    int *ptr, *hash, nb_syms, sym_index, h;
    unsigned char *strtab;

    strtab = s->link->data;
    nb_syms = s->data_offset / sizeof(ElfW(Sym));

    if (!nb_buckets)
        nb_buckets = ((int*)s->hash->data)[0];

    s->hash->data_offset = 0;
    ptr = section_ptr_add(s->hash, (2 + nb_buckets + nb_syms) * sizeof(int));
    ptr[0] = nb_buckets;
    ptr[1] = nb_syms;
    ptr += 2;
    hash = ptr;
    memset(hash, 0, (nb_buckets + 1) * sizeof(int));
    ptr += nb_buckets + 1;

    sym = (ElfW(Sym) *)s->data + 1;
    for(sym_index = 1; sym_index < nb_syms; sym_index++) {
        if (ELFW(ST_BIND)(sym->st_info) != STB_LOCAL) {
            h = elf_hash(strtab + sym->st_name) % nb_buckets;
            *ptr = hash[h];
            hash[h] = sym_index;
        } else {
            *ptr = 0;
        }
        ptr++;
        sym++;
    }
}

/* return the symbol number */
ST_FUNC int put_elf_sym(Section *s, addr_t value, unsigned long size,
    int info, int other, int shndx, const char *name)
{
    int name_offset, sym_index;
    int nbuckets, h;
    ElfW(Sym) *sym;
    Section *hs;

    sym = section_ptr_add(s, sizeof(ElfW(Sym)));
    if (name && name[0])
        name_offset = put_elf_str(s->link, name);
    else
        name_offset = 0;
    /* XXX: endianness */
    sym->st_name = name_offset;
    sym->st_value = value;
    sym->st_size = size;
    sym->st_info = info;
    sym->st_other = other;
    sym->st_shndx = shndx;
    sym_index = sym - (ElfW(Sym) *)s->data;
    hs = s->hash;
    if (hs) {
        int *ptr, *base;
        ptr = section_ptr_add(hs, sizeof(int));
        base = (int *)hs->data;
        /* only add global or weak symbols. */
        if (ELFW(ST_BIND)(info) != STB_LOCAL) {
            /* add another hashing entry */
            nbuckets = base[0];
            h = elf_hash((unsigned char *)s->link->data + name_offset) % nbuckets;
            *ptr = base[2 + h];
            base[2 + h] = sym_index;
            base[1]++;
            /* we resize the hash table */
            hs->nb_hashed_syms++;
            if (hs->nb_hashed_syms > 2 * nbuckets) {
                rebuild_hash(s, 2 * nbuckets);
            }
        } else {
            *ptr = 0;
            base[1]++;
        }
    }
    return sym_index;
}

ST_FUNC int find_elf_sym(Section *s, const char *name)
{
    ElfW(Sym) *sym;
    Section *hs;
    int nbuckets, sym_index, h;
    const char *name1;

    hs = s->hash;
    if (!hs)
        return 0;
    nbuckets = ((int *)hs->data)[0];
    h = elf_hash((unsigned char *) name) % nbuckets;
    sym_index = ((int *)hs->data)[2 + h];
    while (sym_index != 0) {
        sym = &((ElfW(Sym) *)s->data)[sym_index];
        name1 = (char *) s->link->data + sym->st_name;
        if (!strcmp(name, name1))
            return sym_index;
        sym_index = ((int *)hs->data)[2 + nbuckets + sym_index];
    }
    return 0;
}

/* return elf symbol value, signal error if 'err' is nonzero, decorate
   name if FORC */
ST_FUNC addr_t get_sym_addr(TCCState *s1, const char *name, int err, int forc)
{
    int sym_index;
    ElfW(Sym) *sym;
    char buf[256];
    if (forc && s1->leading_underscore
#ifdef TCC_TARGET_PE
        /* win32-32bit stdcall symbols always have _ already */
        && !strchr(name, '@')
#endif
        ) {
        buf[0] = '_';
        pstrcpy(buf + 1, sizeof(buf) - 1, name);
        name = buf;
    }
    sym_index = find_elf_sym(s1->symtab, name);
    sym = &((ElfW(Sym) *)s1->symtab->data)[sym_index];
    if (!sym_index || sym->st_shndx == SHN_UNDEF) {
        if (err)
            tcc_error("%s not defined", name);
        return (addr_t)-1;
    }
    return sym->st_value;
}

/* return elf symbol value */
LIBTCCAPI void *tcc_get_symbol(TCCState *s, const char *name)
{
    addr_t addr = get_sym_addr(s, name, 0, 1);
    return addr == -1 ? NULL : (void*)(uintptr_t)addr;
}

/* list elf symbol names and values */
ST_FUNC void list_elf_symbols(TCCState *s, void *ctx,
    void (*symbol_cb)(void *ctx, const char *name, const void *val))
{
    ElfW(Sym) *sym;
    Section *symtab;
    int sym_index, end_sym;
    const char *name;
    unsigned char sym_vis, sym_bind;

    symtab = s->symtab;
    end_sym = symtab->data_offset / sizeof (ElfSym);
    for (sym_index = 0; sym_index < end_sym; ++sym_index) {
        sym = &((ElfW(Sym) *)symtab->data)[sym_index];
        if (sym->st_value) {
            name = (char *) symtab->link->data + sym->st_name;
            sym_bind = ELFW(ST_BIND)(sym->st_info);
            sym_vis = ELFW(ST_VISIBILITY)(sym->st_other);
            if (sym_bind == STB_GLOBAL && sym_vis == STV_DEFAULT)
                symbol_cb(ctx, name, (void*)(uintptr_t)sym->st_value);
        }
    }
}

/* list elf symbol names and values */
LIBTCCAPI void tcc_list_symbols(TCCState *s, void *ctx,
    void (*symbol_cb)(void *ctx, const char *name, const void *val))
{
    list_elf_symbols(s, ctx, symbol_cb);
}

#ifndef ELF_OBJ_ONLY
static void
version_add (TCCState *s1)
{
    int i;
    ElfW(Sym) *sym;
    ElfW(Verneed) *vn = NULL;
    Section *symtab;
    int sym_index, end_sym, nb_versions = 2, nb_entries = 0;
    ElfW(Half) *versym;
    const char *name;

    if (0 == nb_sym_versions)
        return;
    versym_section = new_section(s1, ".gnu.version", SHT_GNU_versym, SHF_ALLOC);
    versym_section->sh_entsize = sizeof(ElfW(Half));
    versym_section->link = s1->dynsym;

    /* add needed symbols */
    symtab = s1->dynsym;
    end_sym = symtab->data_offset / sizeof (ElfSym);
    versym = section_ptr_add(versym_section, end_sym * sizeof(ElfW(Half)));
    for (sym_index = 1; sym_index < end_sym; ++sym_index) {
        int dllindex, verndx;
        sym = &((ElfW(Sym) *)symtab->data)[sym_index];
        if (sym->st_shndx != SHN_UNDEF)
            continue; /* defined symbol doesn't need library version */
        name = (char *) symtab->link->data + sym->st_name;
        dllindex = find_elf_sym(s1->dynsymtab_section, name);
        verndx = (dllindex && dllindex < nb_sym_to_version)
                 ? sym_to_version[dllindex] : -1;
        if (verndx >= 0) {
            if (!sym_versions[verndx].out_index)
              sym_versions[verndx].out_index = nb_versions++;
            versym[sym_index] = sym_versions[verndx].out_index;
        }
    }
    /* generate verneed section, but not when it will be empty.  Some
       dynamic linkers look at their contents even when DTVERNEEDNUM and
       section size is zero.  */
    if (nb_versions > 2) {
        verneed_section = new_section(s1, ".gnu.version_r",
                                      SHT_GNU_verneed, SHF_ALLOC);
        verneed_section->link = s1->dynsym->link;
        for (i = nb_sym_versions; i-- > 0;) {
            struct sym_version *sv = &sym_versions[i];
            int n_same_libs = 0, prev;
            size_t vnofs;
            ElfW(Vernaux) *vna = 0;
            if (sv->out_index < 1)
              continue;

            /* make sure that a DT_NEEDED tag is put */
            /* abitest-tcc fails on older i386-linux with "ld-linux.so.2" DT_NEEDED
               ret_int_test... Inconsistency detected by ld.so: dl-minimal.c: 148:
               realloc: Assertion `ptr == alloc_last_block' failed! */
            if (strcmp(sv->lib, "ld-linux.so.2"))
                tcc_add_dllref(s1, sv->lib, 0);

            vnofs = section_add(verneed_section, sizeof(*vn), 1);
            vn = (ElfW(Verneed)*)(verneed_section->data + vnofs);
            vn->vn_version = 1;
            vn->vn_file = put_elf_str(verneed_section->link, sv->lib);
            vn->vn_aux = sizeof (*vn);
            do {
                prev = sv->prev_same_lib;
                if (sv->out_index > 0) {
                    vna = section_ptr_add(verneed_section, sizeof(*vna));
                    vna->vna_hash = elf_hash ((const unsigned char *)sv->version);
                    vna->vna_flags = 0;
                    vna->vna_other = sv->out_index;
                    sv->out_index = -2;
                    vna->vna_name = put_elf_str(verneed_section->link, sv->version);
                    vna->vna_next = sizeof (*vna);
                    n_same_libs++;
                }
                if (prev >= 0)
                  sv = &sym_versions[prev];
            } while(prev >= 0);
            vna->vna_next = 0;
            vn = (ElfW(Verneed)*)(verneed_section->data + vnofs);
            vn->vn_cnt = n_same_libs;
            vn->vn_next = sizeof(*vn) + n_same_libs * sizeof(*vna);
            nb_entries++;
        }
        if (vn)
          vn->vn_next = 0;
        verneed_section->sh_info = nb_entries;
    }
    dt_verneednum = nb_entries;
}
#endif /* ndef ELF_OBJ_ONLY */

/* add an elf symbol : check if it is already defined and patch
   it. Return symbol index. NOTE that sh_num can be SHN_UNDEF. */
ST_FUNC int set_elf_sym(Section *s, addr_t value, unsigned long size,
                       int info, int other, int shndx, const char *name)
{
    TCCState *s1 = s->s1;
    ElfW(Sym) *esym;
    int sym_bind, sym_index, sym_type, esym_bind;
    unsigned char sym_vis, esym_vis, new_vis;

    sym_bind = ELFW(ST_BIND)(info);
    sym_type = ELFW(ST_TYPE)(info);
    sym_vis = ELFW(ST_VISIBILITY)(other);

    if (sym_bind != STB_LOCAL) {
        /* we search global or weak symbols */
        sym_index = find_elf_sym(s, name);
        if (!sym_index)
            goto do_def;
        esym = &((ElfW(Sym) *)s->data)[sym_index];
        if (esym->st_value == value && esym->st_size == size && esym->st_info == info
            && esym->st_other == other && esym->st_shndx == shndx)
            return sym_index;
        if (esym->st_shndx != SHN_UNDEF) {
            esym_bind = ELFW(ST_BIND)(esym->st_info);
            /* propagate the most constraining visibility */
            /* STV_DEFAULT(0)<STV_PROTECTED(3)<STV_HIDDEN(2)<STV_INTERNAL(1) */
            esym_vis = ELFW(ST_VISIBILITY)(esym->st_other);
            if (esym_vis == STV_DEFAULT) {
                new_vis = sym_vis;
            } else if (sym_vis == STV_DEFAULT) {
                new_vis = esym_vis;
            } else {
                new_vis = (esym_vis < sym_vis) ? esym_vis : sym_vis;
            }
            esym->st_other = (esym->st_other & ~ELFW(ST_VISIBILITY)(-1))
                             | new_vis;
            if (shndx == SHN_UNDEF) {
                /* ignore adding of undefined symbol if the
                   corresponding symbol is already defined */
            } else if (sym_bind == STB_GLOBAL && esym_bind == STB_WEAK) {
                /* global overrides weak, so patch */
                goto do_patch;
            } else if (sym_bind == STB_WEAK && esym_bind == STB_GLOBAL) {
                /* weak is ignored if already global */
            } else if (sym_bind == STB_WEAK && esym_bind == STB_WEAK) {
                /* keep first-found weak definition, ignore subsequents */
            } else if (sym_vis == STV_HIDDEN || sym_vis == STV_INTERNAL) {
                /* ignore hidden symbols after */
            } else if ((esym->st_shndx == SHN_COMMON
                            || esym->st_shndx == bss_section->sh_num)
                        && (shndx < SHN_LORESERVE
                            && shndx != bss_section->sh_num)) {
                /* data symbol gets precedence over common/bss */
                goto do_patch;
            } else if (shndx == SHN_COMMON || shndx == bss_section->sh_num) {
                /* data symbol keeps precedence over common/bss */
            } else if (s->sh_flags & SHF_DYNSYM) {
                /* we accept that two DLL define the same symbol */
	    } else if (esym->st_other & ST_ASM_SET) {
		/* If the existing symbol came from an asm .set
		   we can override.  */
		goto do_patch;
            } else {
#if 0
                printf("new_bind=%x new_shndx=%x new_vis=%x old_bind=%x old_shndx=%x old_vis=%x\n",
                       sym_bind, shndx, new_vis, esym_bind, esym->st_shndx, esym_vis);
#endif
                tcc_error_noabort("'%s' defined twice", name);
            }
        } else {
            esym->st_other = other;
        do_patch:
            esym->st_info = ELFW(ST_INFO)(sym_bind, sym_type);
            esym->st_shndx = shndx;
            s1->new_undef_sym = 1;
            esym->st_value = value;
            esym->st_size = size;
        }
    } else {
    do_def:
        sym_index = put_elf_sym(s, value, size,
                                ELFW(ST_INFO)(sym_bind, sym_type), other,
                                shndx, name);
    }
    return sym_index;
}

/* put relocation */
ST_FUNC void put_elf_reloca(Section *symtab, Section *s, unsigned long offset,
                            int type, int symbol, addr_t addend)
{
    TCCState *s1 = s->s1;
    char buf[256];
    Section *sr;
    ElfW_Rel *rel;

    sr = s->reloc;
    if (!sr) {
        /* if no relocation section, create it */
        snprintf(buf, sizeof(buf), REL_SECTION_FMT, s->name);
        /* if the symtab is allocated, then we consider the relocation
           are also */
        sr = new_section(s->s1, buf, SHT_RELX, symtab->sh_flags);
        sr->sh_entsize = sizeof(ElfW_Rel);
        sr->link = symtab;
        sr->sh_info = s->sh_num;
        s->reloc = sr;
    }
    rel = section_ptr_add(sr, sizeof(ElfW_Rel));
    rel->r_offset = offset;
    rel->r_info = ELFW(R_INFO)(symbol, type);
#if SHT_RELX == SHT_RELA
    rel->r_addend = addend;
#endif
    if (SHT_RELX != SHT_RELA && addend)
        tcc_error("non-zero addend on REL architecture");
}

ST_FUNC void put_elf_reloc(Section *symtab, Section *s, unsigned long offset,
                           int type, int symbol)
{
    put_elf_reloca(symtab, s, offset, type, symbol, 0);
}

ST_FUNC struct sym_attr *get_sym_attr(TCCState *s1, int index, int alloc)
{
    int n;
    struct sym_attr *tab;

    if (index >= s1->nb_sym_attrs) {
        if (!alloc)
            return s1->sym_attrs;
        /* find immediately bigger power of 2 and reallocate array */
        n = 1;
        while (index >= n)
            n *= 2;
        tab = tcc_realloc(s1->sym_attrs, n * sizeof(*s1->sym_attrs));
        s1->sym_attrs = tab;
        memset(s1->sym_attrs + s1->nb_sym_attrs, 0,
               (n - s1->nb_sym_attrs) * sizeof(*s1->sym_attrs));
        s1->nb_sym_attrs = n;
    }
    return &s1->sym_attrs[index];
}

static void modify_reloctions_old_to_new(TCCState *s1, Section *s, int *old_to_new_syms)
{
    int i, type, sym_index;
    Section *sr;
    ElfW_Rel *rel;

    for(i = 1; i < s1->nb_sections; i++) {
        sr = s1->sections[i];
        if (sr->sh_type == SHT_RELX && sr->link == s) {
            for_each_elem(sr, 0, rel, ElfW_Rel) {
                sym_index = ELFW(R_SYM)(rel->r_info);
                type = ELFW(R_TYPE)(rel->r_info);
                sym_index = old_to_new_syms[sym_index];
                rel->r_info = ELFW(R_INFO)(sym_index, type);
            }
        }
    }
}

/* In an ELF file symbol table, the local symbols must appear below
   the global and weak ones. Since TCC cannot sort it while generating
   the code, we must do it after. All the relocation tables are also
   modified to take into account the symbol table sorting */
static void sort_syms(TCCState *s1, Section *s)
{
    int *old_to_new_syms;
    ElfW(Sym) *new_syms;
    int nb_syms, i;
    ElfW(Sym) *p, *q;

    nb_syms = s->data_offset / sizeof(ElfW(Sym));
    new_syms = tcc_malloc(nb_syms * sizeof(ElfW(Sym)));
    old_to_new_syms = tcc_malloc(nb_syms * sizeof(int));

    /* first pass for local symbols */
    p = (ElfW(Sym) *)s->data;
    q = new_syms;
    for(i = 0; i < nb_syms; i++) {
        if (ELFW(ST_BIND)(p->st_info) == STB_LOCAL) {
            old_to_new_syms[i] = q - new_syms;
            *q++ = *p;
        }
        p++;
    }
    /* save the number of local symbols in section header */
    if( s->sh_size )    /* this 'if' makes IDA happy */
        s->sh_info = q - new_syms;

    /* then second pass for non local symbols */
    p = (ElfW(Sym) *)s->data;
    for(i = 0; i < nb_syms; i++) {
        if (ELFW(ST_BIND)(p->st_info) != STB_LOCAL) {
            old_to_new_syms[i] = q - new_syms;
            *q++ = *p;
        }
        p++;
    }

    /* we copy the new symbols to the old */
    memcpy(s->data, new_syms, nb_syms * sizeof(ElfW(Sym)));
    tcc_free(new_syms);

    modify_reloctions_old_to_new(s1, s, old_to_new_syms);

    tcc_free(old_to_new_syms);
}

#ifndef ELF_OBJ_ONLY
/* See: https://flapenguin.me/elf-dt-gnu-hash */
#define	ELFCLASS_BITS (PTR_SIZE * 8)

static Section *create_gnu_hash(TCCState *s1)
{
    int nb_syms, i, ndef, nbuckets, symoffset, bloom_size, bloom_shift;
    ElfW(Sym) *p;
    Section *gnu_hash;
    Section *dynsym = s1->dynsym;
    Elf32_Word *ptr;

    gnu_hash = new_section(s1, ".gnu.hash", SHT_GNU_HASH, SHF_ALLOC);
    gnu_hash->link = dynsym->hash->link;

    nb_syms = dynsym->data_offset / sizeof(ElfW(Sym));

    /* count def symbols */
    ndef = 0;
    p = (ElfW(Sym) *)dynsym->data;
    for(i = 0; i < nb_syms; i++, p++)
        ndef += p->st_shndx != SHN_UNDEF;

    /* calculate gnu hash sizes and fill header */
    nbuckets = ndef / 4 + 1;
    symoffset = nb_syms - ndef;
    bloom_shift = PTR_SIZE == 8 ? 6 : 5;
    bloom_size = 1; /* must be power of two */
    while (ndef >= bloom_size * (1 << (bloom_shift - 3)))
	bloom_size *= 2;
    ptr = section_ptr_add(gnu_hash, 4 * 4 +
				    PTR_SIZE * bloom_size +
				    nbuckets * 4 +
				    ndef * 4);
    ptr[0] = nbuckets;
    ptr[1] = symoffset;
    ptr[2] = bloom_size;
    ptr[3] = bloom_shift;
    return gnu_hash;
}

static Elf32_Word elf_gnu_hash (const unsigned char *name)
{
    Elf32_Word h = 5381;
    unsigned char c;

    while ((c = *name++))
        h = h * 33 + c;
    return h;
}

static void update_gnu_hash(TCCState *s1, Section *gnu_hash)
{
    int *old_to_new_syms;
    ElfW(Sym) *new_syms;
    int nb_syms, i, nbuckets, bloom_size, bloom_shift;
    ElfW(Sym) *p, *q;
    Section *vs;
    Section *dynsym = s1->dynsym;
    Elf32_Word *ptr, *buckets, *chain, *hash;
    unsigned int *nextbuck;
    addr_t *bloom;
    unsigned char *strtab;
    struct { int first, last; } *buck;

    strtab = dynsym->link->data;
    nb_syms = dynsym->data_offset / sizeof(ElfW(Sym));
    new_syms = tcc_malloc(nb_syms * sizeof(ElfW(Sym)));
    old_to_new_syms = tcc_malloc(nb_syms * sizeof(int));
    hash = tcc_malloc(nb_syms * sizeof(Elf32_Word));
    nextbuck = tcc_malloc(nb_syms * sizeof(int));

    /* calculate hashes and copy undefs */
    p = (ElfW(Sym) *)dynsym->data;
    q = new_syms;
    for(i = 0; i < nb_syms; i++, p++) {
        if (p->st_shndx == SHN_UNDEF) {
            old_to_new_syms[i] = q - new_syms;
            *q++ = *p;
        }
	else
	    hash[i] = elf_gnu_hash(strtab + p->st_name);
    }

    ptr = (Elf32_Word *) gnu_hash->data;
    nbuckets = ptr[0];
    bloom_size = ptr[2];
    bloom_shift = ptr[3];
    bloom = (addr_t *) (void *) &ptr[4];
    buckets = (Elf32_Word*) (void *) &bloom[bloom_size];
    chain = &buckets[nbuckets];
    buck = tcc_malloc(nbuckets * sizeof(*buck));

    if (gnu_hash->data_offset != 4 * 4 +
				 PTR_SIZE * bloom_size +
				 nbuckets * 4 +
				 (nb_syms - (q - new_syms)) * 4)
	tcc_error ("gnu_hash size incorrect");

    /* find buckets */
    for(i = 0; i < nbuckets; i++)
	buck[i].first = -1;

    p = (ElfW(Sym) *)dynsym->data;
    for(i = 0; i < nb_syms; i++, p++)
        if (p->st_shndx != SHN_UNDEF) {
	    int bucket = hash[i] % nbuckets;

	    if (buck[bucket].first == -1)
		buck[bucket].first = buck[bucket].last = i;
	    else {
		nextbuck[buck[bucket].last] = i;
		buck[bucket].last = i;
	    }
	}

    /* fill buckets/chains/bloom and sort symbols */
    p = (ElfW(Sym) *)dynsym->data;
    for(i = 0; i < nbuckets; i++) {
	int cur = buck[i].first;

	if (cur != -1) {
	    buckets[i] = q - new_syms;
	    for (;;) {
                old_to_new_syms[cur] = q - new_syms;
                *q++ = p[cur];
	        *chain++ = hash[cur] & ~1;
		bloom[(hash[cur] / ELFCLASS_BITS) % bloom_size] |=
		    (addr_t)1 << (hash[cur] % ELFCLASS_BITS) |
		    (addr_t)1 << ((hash[cur] >> bloom_shift) % ELFCLASS_BITS);
		if (cur == buck[i].last)
		    break;
		cur = nextbuck[cur];
	    }
	    chain[-1] |= 1;
	}
    }

    memcpy(dynsym->data, new_syms, nb_syms * sizeof(ElfW(Sym)));
    tcc_free(new_syms);
    tcc_free(hash);
    tcc_free(buck);
    tcc_free(nextbuck);

    modify_reloctions_old_to_new(s1, dynsym, old_to_new_syms);

    /* modify the versions */
    vs = versym_section;
    if (vs) {
	ElfW(Half) *newver, *versym = (ElfW(Half) *)vs->data;

	if (1/*versym*/) {
            newver = tcc_malloc(nb_syms * sizeof(*newver));
	    for (i = 0; i < nb_syms; i++)
	        newver[old_to_new_syms[i]] = versym[i];
	    memcpy(vs->data, newver, nb_syms * sizeof(*newver));
	    tcc_free(newver);
	}
    }

    tcc_free(old_to_new_syms);

    /* rebuild hash */
    ptr = (Elf32_Word *) dynsym->hash->data;
    rebuild_hash(dynsym, ptr[0]);
}
#endif /* ELF_OBJ_ONLY */

/* relocate symbol table, resolve undefined symbols if do_resolve is
   true and output error if undefined symbol. */
ST_FUNC void relocate_syms(TCCState *s1, Section *symtab, int do_resolve)
{
    ElfW(Sym) *sym;
    int sym_bind, sh_num;
    const char *name;

    for_each_elem(symtab, 1, sym, ElfW(Sym)) {
        sh_num = sym->st_shndx;
        if (sh_num == SHN_UNDEF) {
            if (do_resolve == 2) /* relocating dynsym */
                continue;
            name = (char *) s1->symtab->link->data + sym->st_name;
            /* Use ld.so to resolve symbol for us (for tcc -run) */
            if (do_resolve) {
#if defined TCC_IS_NATIVE && !defined TCC_TARGET_PE
                /* dlsym() needs the undecorated name.  */
                void *addr = dlsym(RTLD_DEFAULT, &name[s1->leading_underscore]);
#if TARGETOS_OpenBSD || TARGETOS_FreeBSD || TARGETOS_NetBSD || TARGETOS_ANDROID
		if (addr == NULL) {
		    int i;
		    for (i = 0; i < s1->nb_loaded_dlls; i++)
                        if ((addr = dlsym(s1->loaded_dlls[i]->handle, name)))
			    break;
		}
#endif
                if (addr) {
                    sym->st_value = (addr_t) addr;
#ifdef DEBUG_RELOC
		    printf ("relocate_sym: %s -> 0x%lx\n", name, sym->st_value);
#endif
                    goto found;
                }
#endif
            /* if dynamic symbol exist, it will be used in relocate_section */
            } else if (s1->dynsym && find_elf_sym(s1->dynsym, name))
                goto found;
            /* XXX: _fp_hw seems to be part of the ABI, so we ignore
               it */
            if (!strcmp(name, "_fp_hw"))
                goto found;
            /* only weak symbols are accepted to be undefined. Their
               value is zero */
            sym_bind = ELFW(ST_BIND)(sym->st_info);
            if (sym_bind == STB_WEAK)
                sym->st_value = 0;
            else
                tcc_error_noabort("undefined symbol '%s'", name);

        } else if (sh_num < SHN_LORESERVE) {
            /* add section base */
            sym->st_value += s1->sections[sym->st_shndx]->sh_addr;
        }
    found: ;
    }
}

/* relocate a given section (CPU dependent) by applying the relocations
   in the associated relocation section */
static void relocate_section(TCCState *s1, Section *s, Section *sr)
{
    ElfW_Rel *rel;
    ElfW(Sym) *sym;
    int type, sym_index;
    unsigned char *ptr;
    addr_t tgt, addr;
    int is_dwarf = s->sh_num >= s1->dwlo && s->sh_num < s1->dwhi;

    qrel = (ElfW_Rel *)sr->data;
    for_each_elem(sr, 0, rel, ElfW_Rel) {
        ptr = s->data + rel->r_offset;
        sym_index = ELFW(R_SYM)(rel->r_info);
        sym = &((ElfW(Sym) *)symtab_section->data)[sym_index];
        type = ELFW(R_TYPE)(rel->r_info);
        tgt = sym->st_value;
#if SHT_RELX == SHT_RELA
        tgt += rel->r_addend;
#endif
        if (is_dwarf && type == R_DATA_32DW
            && sym->st_shndx >= s1->dwlo && sym->st_shndx < s1->dwhi) {
            /* dwarf section relocation to each other */
            add32le(ptr, tgt - s1->sections[sym->st_shndx]->sh_addr);
            continue;
        }
        addr = s->sh_addr + rel->r_offset;
        relocate(s1, rel, type, ptr, addr, tgt);
    }
#ifndef ELF_OBJ_ONLY
    /* if the relocation is allocated, we change its symbol table */
    if (sr->sh_flags & SHF_ALLOC) {
        sr->link = s1->dynsym;
        if (s1->output_type & TCC_OUTPUT_DYN) {
            size_t r = (uint8_t*)qrel - sr->data;
            if (sizeof ((Stab_Sym*)0)->n_value < PTR_SIZE
                && 0 == strcmp(s->name, ".stab"))
                r = 0; /* cannot apply 64bit relocation to 32bit value */
            sr->data_offset = sr->sh_size = r;
#ifdef CONFIG_TCC_PIE
            if (r && 0 == (s->sh_flags & SHF_WRITE))
                tcc_warning("%d relocations to ro-section %s", (unsigned)(r / sizeof *qrel), s->name);
#endif
        }
    }
#endif
}

/* relocate all sections */
ST_FUNC void relocate_sections(TCCState *s1)
{
    int i;
    Section *s, *sr;

    for (i = 1; i < s1->nb_sections; ++i) {
        sr = s1->sections[i];
        if (sr->sh_type != SHT_RELX)
            continue;
        s = s1->sections[sr->sh_info];
#ifndef TCC_TARGET_MACHO
        if (s != s1->got
            || s1->static_link
            || s1->output_type == TCC_OUTPUT_MEMORY)
#endif
        {
            relocate_section(s1, s, sr);
        }
#ifndef ELF_OBJ_ONLY
        if (sr->sh_flags & SHF_ALLOC) {
            ElfW_Rel *rel;
            /* relocate relocation table in 'sr' */
            for_each_elem(sr, 0, rel, ElfW_Rel)
                rel->r_offset += s->sh_addr;
        }
#endif
    }
}

#ifndef ELF_OBJ_ONLY
/* count the number of dynamic relocations so that we can reserve
   their space */
static int prepare_dynamic_rel(TCCState *s1, Section *sr)
{
    int count = 0;
#if defined(TCC_TARGET_I386) || defined(TCC_TARGET_X86_64) || \
    defined(TCC_TARGET_ARM) || defined(TCC_TARGET_ARM64) || \
    defined(TCC_TARGET_RISCV64)
    ElfW_Rel *rel;
    for_each_elem(sr, 0, rel, ElfW_Rel) {
        int sym_index = ELFW(R_SYM)(rel->r_info);
        int type = ELFW(R_TYPE)(rel->r_info);
        switch(type) {
#if defined(TCC_TARGET_I386)
        case R_386_32:
            if (!get_sym_attr(s1, sym_index, 0)->dyn_index
                && ((ElfW(Sym)*)symtab_section->data + sym_index)->st_shndx == SHN_UNDEF) {
                /* don't fixup unresolved (weak) symbols */
                rel->r_info = ELFW(R_INFO)(sym_index, R_386_RELATIVE);
                break;
            }
#elif defined(TCC_TARGET_X86_64)
        case R_X86_64_32:
        case R_X86_64_32S:
        case R_X86_64_64:
#elif defined(TCC_TARGET_ARM)
        case R_ARM_ABS32:
        case R_ARM_TARGET1:
#elif defined(TCC_TARGET_ARM64)
        case R_AARCH64_ABS32:
        case R_AARCH64_ABS64:
#elif defined(TCC_TARGET_RISCV64)
        case R_RISCV_32:
        case R_RISCV_64:
#endif
            count++;
            break;
#if defined(TCC_TARGET_I386)
        case R_386_PC32:
#elif defined(TCC_TARGET_X86_64)
        case R_X86_64_PC32:
	{
	    ElfW(Sym) *sym = &((ElfW(Sym) *)symtab_section->data)[sym_index];
            /* Hidden defined symbols can and must be resolved locally.
               We're misusing a PLT32 reloc for this, as that's always
               resolved to its address even in shared libs.  */
	    if (sym->st_shndx != SHN_UNDEF &&
		ELFW(ST_VISIBILITY)(sym->st_other) == STV_HIDDEN) {
                rel->r_info = ELFW(R_INFO)(sym_index, R_X86_64_PLT32);
	        break;
	    }
	}
#elif defined(TCC_TARGET_ARM64)
        case R_AARCH64_PREL32:
#endif
            if (s1->output_type != TCC_OUTPUT_DLL)
                break;
            if (get_sym_attr(s1, sym_index, 0)->dyn_index)
                count++;
            break;
        default:
            break;
        }
    }
#endif
    return count;
}
#endif

#ifdef NEED_BUILD_GOT
static int build_got(TCCState *s1)
{
    /* if no got, then create it */
    s1->got = new_section(s1, ".got", SHT_PROGBITS, SHF_ALLOC | SHF_WRITE);
    s1->got->sh_entsize = 4;
    /* keep space for _DYNAMIC pointer and two dummy got entries */
    section_ptr_add(s1->got, 3 * PTR_SIZE);
    return set_elf_sym(symtab_section, 0, 0, ELFW(ST_INFO)(STB_GLOBAL, STT_OBJECT),
        0, s1->got->sh_num, "_GLOBAL_OFFSET_TABLE_");
}

/* Create a GOT and (for function call) a PLT entry corresponding to a symbol
   in s1->symtab. When creating the dynamic symbol table entry for the GOT
   relocation, use 'size' and 'info' for the corresponding symbol metadata.
   Returns the offset of the GOT or (if any) PLT entry. */
static struct sym_attr * put_got_entry(TCCState *s1, int dyn_reloc_type,
                                       int sym_index)
{
    int need_plt_entry;
    const char *name;
    ElfW(Sym) *sym;
    struct sym_attr *attr;
    unsigned got_offset;
    char plt_name[200];
    int len;
    Section *s_rel;

    need_plt_entry = (dyn_reloc_type == R_JMP_SLOT);
    attr = get_sym_attr(s1, sym_index, 1);

    /* In case a function is both called and its address taken 2 GOT entries
       are created, one for taking the address (GOT) and the other for the PLT
       entry (PLTGOT).  */
    if (need_plt_entry ? attr->plt_offset : attr->got_offset)
        return attr;

    s_rel = s1->got;
    if (need_plt_entry) {
        if (!s1->plt) {
            s1->plt = new_section(s1, ".plt", SHT_PROGBITS, SHF_ALLOC | SHF_EXECINSTR);
            s1->plt->sh_entsize = 4;
        }
        s_rel = s1->plt;
    }

    /* create the GOT entry */
    got_offset = s1->got->data_offset;
    section_ptr_add(s1->got, PTR_SIZE);

    /* Create the GOT relocation that will insert the address of the object or
       function of interest in the GOT entry. This is a static relocation for
       memory output (dlsym will give us the address of symbols) and dynamic
       relocation otherwise (executable and DLLs). The relocation should be
       done lazily for GOT entry with *_JUMP_SLOT relocation type (the one
       associated to a PLT entry) but is currently done at load time for an
       unknown reason. */

    sym = &((ElfW(Sym) *) symtab_section->data)[sym_index];
    name = (char *) symtab_section->link->data + sym->st_name;
    //printf("sym %d %s\n", need_plt_entry, name);

    if (s1->dynsym) {
	if (ELFW(ST_BIND)(sym->st_info) == STB_LOCAL) {
	    /* Hack alarm.  We don't want to emit dynamic symbols
	       and symbol based relocs for STB_LOCAL symbols, but rather
	       want to resolve them directly.  At this point the symbol
	       values aren't final yet, so we must defer this.  We will later
	       have to create a RELATIVE reloc anyway, so we misuse the
	       relocation slot to smuggle the symbol reference until
	       fill_local_got_entries.  Not that the sym_index is
	       relative to symtab_section, not s1->dynsym!  Nevertheless
	       we use s1->dyn_sym so that if this is the first call
	       that got->reloc is correctly created.  Also note that
	       RELATIVE relocs are not normally created for the .got,
	       so the types serves as a marker for later (and is retained
	       also for the final output, which is okay because then the
	       got is just normal data).  */
	    put_elf_reloc(s1->dynsym, s1->got, got_offset, R_RELATIVE,
			  sym_index);
	} else {
	    if (0 == attr->dyn_index)
                attr->dyn_index = set_elf_sym(s1->dynsym, sym->st_value,
                                              sym->st_size, sym->st_info, 0,
                                              sym->st_shndx, name);
	    put_elf_reloc(s1->dynsym, s_rel, got_offset, dyn_reloc_type,
			  attr->dyn_index);
	}
    } else {
        put_elf_reloc(symtab_section, s1->got, got_offset, dyn_reloc_type,
                      sym_index);
    }

    if (need_plt_entry) {
        attr->plt_offset = create_plt_entry(s1, got_offset, attr);

        /* create a symbol 'sym@plt' for the PLT jump vector */
        len = strlen(name);
        if (len > sizeof plt_name - 5)
            len = sizeof plt_name - 5;
        memcpy(plt_name, name, len);
        strcpy(plt_name + len, "@plt");
        attr->plt_sym = put_elf_sym(s1->symtab, attr->plt_offset, 0,
            ELFW(ST_INFO)(STB_GLOBAL, STT_FUNC), 0, s1->plt->sh_num, plt_name);
    } else {
        attr->got_offset = got_offset;
    }

    return attr;
}

/* build GOT and PLT entries */
/* Two passes because R_JMP_SLOT should become first. Some targets
   (arm, arm64) do not allow mixing R_JMP_SLOT and R_GLOB_DAT. */
ST_FUNC void build_got_entries(TCCState *s1, int got_sym)
{
    Section *s;
    ElfW_Rel *rel;
    ElfW(Sym) *sym;
    int i, type, gotplt_entry, reloc_type, sym_index;
    struct sym_attr *attr;
    int pass = 0;
redo:
    for(i = 1; i < s1->nb_sections; i++) {
        s = s1->sections[i];
        if (s->sh_type != SHT_RELX)
            continue;
        /* no need to handle got relocations */
        if (s->link != symtab_section)
            continue;
        for_each_elem(s, 0, rel, ElfW_Rel) {
            type = ELFW(R_TYPE)(rel->r_info);
            gotplt_entry = gotplt_entry_type(type);
            if (gotplt_entry == -1)
                tcc_error ("Unknown relocation type for got: %d", type);
            sym_index = ELFW(R_SYM)(rel->r_info);
            sym = &((ElfW(Sym) *)symtab_section->data)[sym_index];

            if (gotplt_entry == NO_GOTPLT_ENTRY) {
                continue;
            }

            /* Automatically create PLT/GOT [entry] if it is an undefined
	       reference (resolved at runtime), or the symbol is absolute,
	       probably created by tcc_add_symbol, and thus on 64-bit
	       targets might be too far from application code.  */
            if (gotplt_entry == AUTO_GOTPLT_ENTRY) {
                if (sym->st_shndx == SHN_UNDEF) {
                    ElfW(Sym) *esym;
		    int dynindex;
                    if (!PCRELATIVE_DLLPLT
                        && (s1->output_type & TCC_OUTPUT_DYN))
                        continue;
		    /* Relocations for UNDEF symbols would normally need
		       to be transferred into the executable or shared object.
		       If that were done AUTO_GOTPLT_ENTRY wouldn't exist.
		       But TCC doesn't do that (at least for exes), so we
		       need to resolve all such relocs locally.  And that
		       means PLT slots for functions in DLLs and COPY relocs for
		       data symbols.  COPY relocs were generated in
		       bind_exe_dynsyms (and the symbol adjusted to be defined),
		       and for functions we were generated a dynamic symbol
		       of function type.  */
		    if (s1->dynsym) {
			/* dynsym isn't set for -run :-/  */
			dynindex = get_sym_attr(s1, sym_index, 0)->dyn_index;
			esym = (ElfW(Sym) *)s1->dynsym->data + dynindex;
			if (dynindex
			    && (ELFW(ST_TYPE)(esym->st_info) == STT_FUNC
				|| (ELFW(ST_TYPE)(esym->st_info) == STT_NOTYPE
				    && ELFW(ST_TYPE)(sym->st_info) == STT_FUNC)))
			    goto jmp_slot;
		    }
                } else if (sym->st_shndx == SHN_ABS) {
                    if (sym->st_value == 0) /* from tcc_add_btstub() */
                        continue;
#ifndef TCC_TARGET_ARM
                    if (PTR_SIZE != 8)
                        continue;
#endif
                    /* from tcc_add_symbol(): on 64 bit platforms these
                       need to go through .got */
                } else
                    continue;
            }

#ifdef TCC_TARGET_X86_64
            if ((type == R_X86_64_PLT32 || type == R_X86_64_PC32) &&
		sym->st_shndx != SHN_UNDEF &&
                (ELFW(ST_VISIBILITY)(sym->st_other) != STV_DEFAULT ||
		 ELFW(ST_BIND)(sym->st_info) == STB_LOCAL ||
		 s1->output_type & TCC_OUTPUT_EXE)) {
		if (pass != 0)
		    continue;
                rel->r_info = ELFW(R_INFO)(sym_index, R_X86_64_PC32);
                continue;
            }
#endif
            reloc_type = code_reloc(type);
            if (reloc_type == -1)
                tcc_error ("Unknown relocation type: %d", type);

            if (reloc_type != 0) {
        jmp_slot:
	        if (pass != 0)
                    continue;
                reloc_type = R_JMP_SLOT;
            } else {
	        if (pass != 1)
                    continue;
                reloc_type = R_GLOB_DAT;
            }

            if (!s1->got)
                got_sym = build_got(s1);

            if (gotplt_entry == BUILD_GOT_ONLY)
                continue;

            attr = put_got_entry(s1, reloc_type, sym_index);

            if (reloc_type == R_JMP_SLOT)
                rel->r_info = ELFW(R_INFO)(attr->plt_sym, type);
        }
    }
    if (++pass < 2)
        goto redo;
    /* .rel.plt refers to .got actually */
    if (s1->plt && s1->plt->reloc)
        s1->plt->reloc->sh_info = s1->got->sh_num;
    if (got_sym) /* set size */
        ((ElfW(Sym)*)symtab_section->data)[got_sym].st_size = s1->got->data_offset;
}
#endif /* def NEED_BUILD_GOT */

ST_FUNC int set_global_sym(TCCState *s1, const char *name, Section *sec, addr_t offs)
{
    int shn = sec ? sec->sh_num : offs || !name ? SHN_ABS : SHN_UNDEF;
    if (sec && offs == -1)
        offs = sec->data_offset;
    return set_elf_sym(symtab_section, offs, 0,
        ELFW(ST_INFO)(name ? STB_GLOBAL : STB_LOCAL, STT_NOTYPE), 0, shn, name);
}

static void add_init_array_defines(TCCState *s1, const char *section_name)
{
    Section *s;
    addr_t end_offset;
    char buf[1024];
    s = have_section(s1, section_name);
    if (!s || !(s->sh_flags & SHF_ALLOC)) {
        end_offset = 0;
        s = data_section;
    } else {
        end_offset = s->data_offset;
    }
    snprintf(buf, sizeof(buf), "__%s_start", section_name + 1);
    set_global_sym(s1, buf, s, 0);
    snprintf(buf, sizeof(buf), "__%s_end", section_name + 1);
    set_global_sym(s1, buf, s, end_offset);
}

ST_FUNC void add_array (TCCState *s1, const char *sec, int c)
{
    Section *s;
    s = find_section(s1, sec);
    s->sh_flags = shf_RELRO;
    s->sh_type = sec[1] == 'i' ? SHT_INIT_ARRAY : SHT_FINI_ARRAY;
    put_elf_reloc (s1->symtab, s, s->data_offset, R_DATA_PTR, c);
    section_ptr_add(s, PTR_SIZE);
}

#ifdef CONFIG_TCC_BCHECK
ST_FUNC void tcc_add_bcheck(TCCState *s1)
{
    if (0 == s1->do_bounds_check)
        return;
    section_ptr_add(bounds_section, sizeof(addr_t));
}
#endif

/* set symbol to STB_LOCAL and resolve. The point is to not export it as
   a dynamic symbol to allow so's to have one each with a different value. */
static void set_local_sym(TCCState *s1, const char *name, Section *s, int offset)
{
    int c = find_elf_sym(s1->symtab, name);
    if (c) {
        ElfW(Sym) *esym = (ElfW(Sym)*)s1->symtab->data + c;
        esym->st_info = ELFW(ST_INFO)(STB_LOCAL, STT_NOTYPE);
        esym->st_value = offset;
        esym->st_shndx = s->sh_num;
    }
}

/* avoid generating debug/test_coverage code for stub functions */
static void tcc_compile_string_no_debug(TCCState *s, const char *str)
{
    int save_do_debug = s->do_debug;
    int save_test_coverage = s->test_coverage;

    s->do_debug = 0;
    s->test_coverage = 0;
    tcc_compile_string(s, str);
    s->do_debug = save_do_debug;
    s->test_coverage = save_test_coverage;
}

#ifdef CONFIG_TCC_BACKTRACE
static void put_ptr(TCCState *s1, Section *s, int offs)
{
    int c;
    c = set_global_sym(s1, NULL, s, offs);
    s = data_section;
    put_elf_reloc (s1->symtab, s, s->data_offset, R_DATA_PTR, c);
    section_ptr_add(s, PTR_SIZE);
}

ST_FUNC void tcc_add_btstub(TCCState *s1)
{
    Section *s;
    int n, o;
    CString cstr;

    s = data_section;
    /* Align to PTR_SIZE */
    section_ptr_add(s, -s->data_offset & (PTR_SIZE - 1));
    o = s->data_offset;
    /* create (part of) a struct rt_context (see tccrun.c) */
    if (s1->dwarf) {
        put_ptr(s1, dwarf_line_section, 0);
        put_ptr(s1, dwarf_line_section, -1);
	if (s1->dwarf >= 5)
            put_ptr(s1, dwarf_line_str_section, 0);
	else
            put_ptr(s1, dwarf_str_section, 0);
    }
    else
    {
        put_ptr(s1, stab_section, 0);
        put_ptr(s1, stab_section, -1);
        put_ptr(s1, stab_section->link, 0);
    }
    *(addr_t *)section_ptr_add(s, PTR_SIZE) = s1->dwarf;
    /* skip esym_start/esym_end/elf_str (not loaded) */
    section_ptr_add(s, 3 * PTR_SIZE);
    /* prog_base : local nameless symbol with offset 0 at SHN_ABS */
    put_ptr(s1, NULL, 0);
#if defined TCC_TARGET_MACHO
    /* adjust for __PAGEZERO */
    write64le(data_section->data + data_section->data_offset - PTR_SIZE,
	      (uint64_t)1 << 32);
#endif
    n = 2 * PTR_SIZE;
#ifdef CONFIG_TCC_BCHECK
    if (s1->do_bounds_check) {
        put_ptr(s1, bounds_section, 0);
        n -= PTR_SIZE;
    }
#endif
    section_ptr_add(s, n);
    cstr_new(&cstr);
    cstr_printf(&cstr,
        "extern void __bt_init(),__bt_exit(),__bt_init_dll();"
        "static void *__rt_info[];"
        "__attribute__((constructor)) static void __bt_init_rt(){");
#ifdef TCC_TARGET_PE
    if (s1->output_type == TCC_OUTPUT_DLL)
#ifdef CONFIG_TCC_BCHECK
        cstr_printf(&cstr, "__bt_init_dll(%d);", s1->do_bounds_check);
#else
        cstr_printf(&cstr, "__bt_init_dll(0);");
#endif
#endif
    cstr_printf(&cstr, "__bt_init(__rt_info,%d);}",
        s1->output_type == TCC_OUTPUT_DLL ? 0 : s1->rt_num_callers + 1);
    /* In case dlcose is called by application */
    cstr_printf(&cstr,
        "__attribute__((destructor)) static void __bt_exit_rt(){"
        "__bt_exit(__rt_info);}");
    tcc_compile_string_no_debug(s1, cstr.data);
    cstr_free(&cstr);
    set_local_sym(s1, &"___rt_info"[!s1->leading_underscore], s, o);
}
#endif /* def CONFIG_TCC_BACKTRACE */

static void tcc_tcov_add_file(TCCState *s1, const char *filename)
{
    CString cstr;
    void *ptr;
    char wd[1024];

    if (tcov_section == NULL)
        return;
    section_ptr_add(tcov_section, 1);
    write32le (tcov_section->data, tcov_section->data_offset);

    cstr_new (&cstr);
    if (filename[0] == '/')
        cstr_printf (&cstr, "%s.tcov", filename);
    else {
        getcwd (wd, sizeof(wd));
        cstr_printf (&cstr, "%s/%s.tcov", wd, filename);
    }
    ptr = section_ptr_add(tcov_section, cstr.size + 1);
    strcpy((char *)ptr, cstr.data);
    unlink((char *)ptr);
#ifdef _WIN32
    normalize_slashes((char *)ptr);
#endif
    cstr_free (&cstr);

    cstr_new(&cstr);
    cstr_printf(&cstr,
        "extern char *__tcov_data[];"
        "extern void __store_test_coverage ();"
        "__attribute__((destructor)) static void __tcov_exit() {"
        "__store_test_coverage(__tcov_data);"
        "}");
    tcc_compile_string_no_debug(s1, cstr.data);
    cstr_free(&cstr);
    set_local_sym(s1, &"___tcov_data"[!s1->leading_underscore], tcov_section, 0);
}

#ifndef TCC_TARGET_PE
/* add tcc runtime libraries */
ST_FUNC void tcc_add_runtime(TCCState *s1)
{
    s1->filetype = 0;

#ifdef CONFIG_TCC_BCHECK
    tcc_add_bcheck(s1);
#endif
    tcc_add_pragma_libs(s1);

    /* add libc */
    if (!s1->nostdlib) {
        int lpthread = s1->option_pthread;

#ifdef CONFIG_TCC_BCHECK
        if (s1->do_bounds_check && s1->output_type != TCC_OUTPUT_DLL) {
            tcc_add_support(s1, "bcheck.o");
# if !(TARGETOS_OpenBSD || TARGETOS_NetBSD)
            tcc_add_library_err(s1, "dl");
# endif
            lpthread = 1;
        }
#endif
#ifdef CONFIG_TCC_BACKTRACE
        if (s1->do_backtrace) {
            if (s1->output_type & TCC_OUTPUT_EXE)
                tcc_add_support(s1, "bt-exe.o");
            if (s1->output_type != TCC_OUTPUT_DLL)
                tcc_add_support(s1, "bt-log.o");
            if (s1->output_type != TCC_OUTPUT_MEMORY)
                tcc_add_btstub(s1);
        }
#endif
        if (lpthread)
            tcc_add_library_err(s1, "pthread");
        tcc_add_library_err(s1, "c");
#ifdef TCC_LIBGCC
        if (!s1->static_link) {
            if (TCC_LIBGCC[0] == '/')
                tcc_add_file(s1, TCC_LIBGCC);
            else
                tcc_add_dll(s1, TCC_LIBGCC, 0);
        }
#endif
#if defined TCC_TARGET_ARM && TARGETOS_FreeBSD
        tcc_add_library_err(s1, "gcc_s"); // unwind code
#endif
        if (TCC_LIBTCC1[0])
            tcc_add_support(s1, TCC_LIBTCC1);

        /* add crt end if not memory output */
	if (s1->output_type != TCC_OUTPUT_MEMORY) {
#if defined TCC_TARGET_MACHO
            /* nothing to do */
#elif TARGETOS_FreeBSD || TARGETOS_NetBSD
	    if (s1->output_type & TCC_OUTPUT_DYN)
	        tcc_add_crt(s1, "crtendS.o");
	    else
	        tcc_add_crt(s1, "crtend.o");
            tcc_add_crt(s1, "crtn.o");
#elif TARGETOS_OpenBSD
	    if (s1->output_type == TCC_OUTPUT_DLL)
	        tcc_add_crt(s1, "crtendS.o");
	    else
	        tcc_add_crt(s1, "crtend.o");
#elif TARGETOS_ANDROID
	    if (s1->output_type == TCC_OUTPUT_DLL)
                tcc_add_crt(s1, "crtend_so.o");
            else
                tcc_add_crt(s1, "crtend_android.o");
#else
            tcc_add_crt(s1, "crtn.o");
#endif
        }
    }
}
#endif /* ndef TCC_TARGET_PE */

/* add various standard linker symbols (must be done after the
   sections are filled (for example after allocating common
   symbols)) */
static void tcc_add_linker_symbols(TCCState *s1)
{
    char buf[1024];
    int i;
    Section *s;

    set_global_sym(s1, "_etext", text_section, -1);
    set_global_sym(s1, "_edata", data_section, -1);
    set_global_sym(s1, "_end", bss_section, -1);
#if TARGETOS_OpenBSD
    set_global_sym(s1, "__executable_start", NULL, ELF_START_ADDR);
#endif
#ifdef TCC_TARGET_RISCV64
    /* XXX should be .sdata+0x800, not .data+0x800 */
    set_global_sym(s1, "__global_pointer$", data_section, 0x800);
#endif
    /* horrible new standard ldscript defines */
    add_init_array_defines(s1, ".preinit_array");
    add_init_array_defines(s1, ".init_array");
    add_init_array_defines(s1, ".fini_array");
    /* add start and stop symbols for sections whose name can be
       expressed in C */
    for(i = 1; i < s1->nb_sections; i++) {
        s = s1->sections[i];
        if ((s->sh_flags & SHF_ALLOC)
            && (s->sh_type == SHT_PROGBITS
                || s->sh_type == SHT_STRTAB)) {
            const char *p;
            /* check if section name can be expressed in C */
            p = s->name;
            for(;;) {
                int c = *p;
                if (!c)
                    break;
                if (!isid(c) && !isnum(c))
                    goto next_sec;
                p++;
            }
            snprintf(buf, sizeof(buf), "__start_%s", s->name);
            set_global_sym(s1, buf, s, 0);
            snprintf(buf, sizeof(buf), "__stop_%s", s->name);
            set_global_sym(s1, buf, s, -1);
        }
    next_sec: ;
    }
}

ST_FUNC void resolve_common_syms(TCCState *s1)
{
    ElfW(Sym) *sym;

    /* Allocate common symbols in BSS.  */
    for_each_elem(symtab_section, 1, sym, ElfW(Sym)) {
        if (sym->st_shndx == SHN_COMMON) {
            /* symbol alignment is in st_value for SHN_COMMONs */
	    sym->st_value = section_add(bss_section, sym->st_size,
					sym->st_value);
            sym->st_shndx = bss_section->sh_num;
        }
    }

    /* Now assign linker provided symbols their value.  */
    tcc_add_linker_symbols(s1);
}

#ifndef ELF_OBJ_ONLY
ST_FUNC void fill_got_entry(TCCState *s1, ElfW_Rel *rel)
{
    int sym_index = ELFW(R_SYM) (rel->r_info);
    ElfW(Sym) *sym = &((ElfW(Sym) *) symtab_section->data)[sym_index];
    struct sym_attr *attr = get_sym_attr(s1, sym_index, 0);
    unsigned offset = attr->got_offset;

    if (0 == offset)
        return;
    section_reserve(s1->got, offset + PTR_SIZE);
#if PTR_SIZE == 8
    write64le(s1->got->data + offset, sym->st_value);
#else
    write32le(s1->got->data + offset, sym->st_value);
#endif
}

/* Perform relocation to GOT or PLT entries */
ST_FUNC void fill_got(TCCState *s1)
{
    Section *s;
    ElfW_Rel *rel;
    int i;

    for(i = 1; i < s1->nb_sections; i++) {
        s = s1->sections[i];
        if (s->sh_type != SHT_RELX)
            continue;
        /* no need to handle got relocations */
        if (s->link != symtab_section)
            continue;
        for_each_elem(s, 0, rel, ElfW_Rel) {
            switch (ELFW(R_TYPE) (rel->r_info)) {
                case R_X86_64_GOT32:
                case R_X86_64_GOTPCREL:
		case R_X86_64_GOTPCRELX:
		case R_X86_64_REX_GOTPCRELX:
                case R_X86_64_PLT32:
                    fill_got_entry(s1, rel);
                    break;
            }
        }
    }
}

/* See put_got_entry for a description.  This is the second stage
   where GOT references to local defined symbols are rewritten.  */
static void fill_local_got_entries(TCCState *s1)
{
    ElfW_Rel *rel;
    if (!s1->got->reloc)
        return;
    for_each_elem(s1->got->reloc, 0, rel, ElfW_Rel) {
	if (ELFW(R_TYPE)(rel->r_info) == R_RELATIVE) {
	    int sym_index = ELFW(R_SYM) (rel->r_info);
	    ElfW(Sym) *sym = &((ElfW(Sym) *) symtab_section->data)[sym_index];
	    struct sym_attr *attr = get_sym_attr(s1, sym_index, 0);
	    unsigned offset = attr->got_offset;
	    if (offset != rel->r_offset - s1->got->sh_addr)
	      tcc_error_noabort("huh");
	    rel->r_info = ELFW(R_INFO)(0, R_RELATIVE);
#if SHT_RELX == SHT_RELA
	    rel->r_addend = sym->st_value;
#else
	    /* All our REL architectures also happen to be 32bit LE.  */
	    write32le(s1->got->data + offset, sym->st_value);
#endif
	}
    }
}

/* Bind symbols of executable: resolve undefined symbols from exported symbols
   in shared libraries */
static void bind_exe_dynsyms(TCCState *s1)
{
    const char *name;
    int sym_index, index;
    ElfW(Sym) *sym, *esym;
    int type;

    /* Resolve undefined symbols from dynamic symbols. When there is a match:
       - if STT_FUNC or STT_GNU_IFUNC symbol -> add it in PLT
       - if STT_OBJECT symbol -> add it in .bss section with suitable reloc */
    for_each_elem(symtab_section, 1, sym, ElfW(Sym)) {
        if (sym->st_shndx == SHN_UNDEF) {
            name = (char *) symtab_section->link->data + sym->st_name;
            sym_index = find_elf_sym(s1->dynsymtab_section, name);
            if (sym_index) {
                esym = &((ElfW(Sym) *)s1->dynsymtab_section->data)[sym_index];
                type = ELFW(ST_TYPE)(esym->st_info);
                if ((type == STT_FUNC) || (type == STT_GNU_IFUNC)) {
                    /* Indirect functions shall have STT_FUNC type in executable
                     * dynsym section. Indeed, a dlsym call following a lazy
                     * resolution would pick the symbol value from the
                     * executable dynsym entry which would contain the address
                     * of the function wanted by the caller of dlsym instead of
                     * the address of the function that would return that
                     * address */
                    int dynindex
		      = put_elf_sym(s1->dynsym, 0, esym->st_size,
				    ELFW(ST_INFO)(STB_GLOBAL,STT_FUNC), 0, 0,
				    name);
		    int index = sym - (ElfW(Sym) *) symtab_section->data;
		    get_sym_attr(s1, index, 1)->dyn_index = dynindex;
                } else if (type == STT_OBJECT) {
                    unsigned long offset;
                    ElfW(Sym) *dynsym;
                    offset = bss_section->data_offset;
                    /* XXX: which alignment ? */
                    offset = (offset + 16 - 1) & -16;
                    set_elf_sym (s1->symtab, offset, esym->st_size,
                                 esym->st_info, 0, bss_section->sh_num, name);
                    index = put_elf_sym(s1->dynsym, offset, esym->st_size,
                                        esym->st_info, 0, bss_section->sh_num,
                                        name);

                    /* Ensure R_COPY works for weak symbol aliases */
                    if (ELFW(ST_BIND)(esym->st_info) == STB_WEAK) {
                        for_each_elem(s1->dynsymtab_section, 1, dynsym, ElfW(Sym)) {
                            if ((dynsym->st_value == esym->st_value)
                                && (ELFW(ST_BIND)(dynsym->st_info) == STB_GLOBAL)) {
                                char *dynname = (char *) s1->dynsymtab_section->link->data
                                                + dynsym->st_name;
                                put_elf_sym(s1->dynsym, offset, dynsym->st_size,
                                            dynsym->st_info, 0,
                                            bss_section->sh_num, dynname);
                                break;
                            }
                        }
                    }

                    put_elf_reloc(s1->dynsym, bss_section,
                                  offset, R_COPY, index);
                    offset += esym->st_size;
                    bss_section->data_offset = offset;
                }
            } else {
                /* STB_WEAK undefined symbols are accepted */
                /* XXX: _fp_hw seems to be part of the ABI, so we ignore it */
                if (ELFW(ST_BIND)(sym->st_info) == STB_WEAK ||
                    !strcmp(name, "_fp_hw")) {
                } else {
                    tcc_error_noabort("undefined symbol '%s'", name);
                }
            }
        }
    }
}

/* Bind symbols of libraries: export all non local symbols of executable that
   are referenced by shared libraries. The reason is that the dynamic loader
   search symbol first in executable and then in libraries. Therefore a
   reference to a symbol already defined by a library can still be resolved by
   a symbol in the executable.   With -rdynamic, export all defined symbols */
static void bind_libs_dynsyms(TCCState *s1)
{
    const char *name;
    int dynsym_index;
    ElfW(Sym) *sym, *esym;

    for_each_elem(symtab_section, 1, sym, ElfW(Sym)) {
        name = (char *)symtab_section->link->data + sym->st_name;
        dynsym_index = find_elf_sym(s1->dynsymtab_section, name);
        if (sym->st_shndx != SHN_UNDEF
            && ELFW(ST_BIND)(sym->st_info) != STB_LOCAL) {
            if (dynsym_index || s1->rdynamic)
                set_elf_sym(s1->dynsym, sym->st_value, sym->st_size,
                            sym->st_info, 0, sym->st_shndx, name);
        } else if (dynsym_index) {
            esym = (ElfW(Sym) *)s1->dynsymtab_section->data + dynsym_index;
            if (esym->st_shndx == SHN_UNDEF) {
                /* weak symbols can stay undefined */
                if (ELFW(ST_BIND)(esym->st_info) != STB_WEAK)
                    tcc_warning("undefined dynamic symbol '%s'", name);
            }
        }
    }
}

/* Export all non local symbols. This is used by shared libraries so that the
   non local symbols they define can resolve a reference in another shared
   library or in the executable. Correspondingly, it allows undefined local
   symbols to be resolved by other shared libraries or by the executable. */
static void export_global_syms(TCCState *s1)
{
    int dynindex, index;
    const char *name;
    ElfW(Sym) *sym;
    for_each_elem(symtab_section, 1, sym, ElfW(Sym)) {
        if (ELFW(ST_BIND)(sym->st_info) != STB_LOCAL) {
	    name = (char *) symtab_section->link->data + sym->st_name;
	    dynindex = set_elf_sym(s1->dynsym, sym->st_value, sym->st_size,
				   sym->st_info, 0, sym->st_shndx, name);
	    index = sym - (ElfW(Sym) *) symtab_section->data;
            get_sym_attr(s1, index, 1)->dyn_index = dynindex;
        }
    }
}

/* decide if an unallocated section should be output. */
static int set_sec_sizes(TCCState *s1)
{
    int i;
    Section *s;
    int textrel = 0;
    int file_type = s1->output_type;

    /* Allocate strings for section names */
    for(i = 1; i < s1->nb_sections; i++) {
        s = s1->sections[i];
        if (s->sh_type == SHT_RELX && !(s->sh_flags & SHF_ALLOC)) {
            /* when generating a DLL, we include relocations but
               we may patch them */
            if ((file_type & TCC_OUTPUT_DYN)
                && (s1->sections[s->sh_info]->sh_flags & SHF_ALLOC)) {
                int count = prepare_dynamic_rel(s1, s);
                if (count) {
                    /* allocate the section */
                    s->sh_flags |= SHF_ALLOC;
                    s->sh_size = count * sizeof(ElfW_Rel);
                    if (!(s1->sections[s->sh_info]->sh_flags & SHF_WRITE))
                        textrel += count;
                }
            }
        } else if ((s->sh_flags & SHF_ALLOC)
#ifdef TCC_TARGET_ARM
                   || s->sh_type == SHT_ARM_ATTRIBUTES
#endif
                   || s1->do_debug) {
            s->sh_size = s->data_offset;
        }

#ifdef TCC_TARGET_ARM
        /* XXX: Suppress stack unwinding section. */
        if (s->sh_type == SHT_ARM_EXIDX) {
            s->sh_flags = 0;
            s->sh_size = 0;
        }
#endif

    }
    return textrel;
}

/* various data used under elf_output_file() */
struct dyn_inf {
    Section *dynamic;
    Section *dynstr;
    struct {
        /* Info to be copied in dynamic section */
        unsigned long data_offset;
        addr_t rel_addr;
        addr_t rel_size;
    };

    ElfW(Phdr) *phdr;
    int phnum;
    Section *interp;
    Section *note;
    Section *gnu_hash;

    /* read only segment mapping for GNU_RELRO */
    Section _roinf, *roinf;
};

/* Decide the layout of sections loaded in memory. This must be done before
   program headers are filled since they contain info about the layout.
   We do the following ordering: interp, symbol tables, relocations, progbits,
   nobits */
static int sort_sections(TCCState *s1, int *sec_order, Section *interp)
{
    Section *s;
    int i, j, k, f, f0, n;
    int nb_sections = s1->nb_sections;
    int *sec_cls = sec_order + nb_sections;

    for (i = 1; i < nb_sections; i++) {
        s = s1->sections[i];
        if (s->sh_flags & SHF_ALLOC) {
            j = 0x100;
            if (s->sh_flags & SHF_WRITE)
                j = 0x200;
            if (s->sh_flags & SHF_TLS)
                j += 0x200;
        } else if (s->sh_name) {
            j = 0x700;
        } else {
            j = 0x900; /* no sh_name: won't go to file */
        }
        if (s->sh_type == SHT_SYMTAB || s->sh_type == SHT_DYNSYM) {
            k = 0x10;
        } else if (s->sh_type == SHT_STRTAB && strcmp(s->name, ".stabstr")) {
            k = 0x11;
            if (i == nb_sections - 1) /* ".shstrtab" assumed to remain last */
                k = 0xff;
        } else if (s->sh_type == SHT_HASH || s->sh_type == SHT_GNU_HASH) {
            k = 0x12;
        } else if (s->sh_type == SHT_RELX) {
            k = 0x20;
            if (s1->plt && s == s1->plt->reloc)
                k = 0x21;
        } else if (s->sh_type == SHT_PREINIT_ARRAY) {
            k = 0x41;
        } else if (s->sh_type == SHT_INIT_ARRAY) {
            k = 0x42;
        } else if (s->sh_type == SHT_FINI_ARRAY) {
            k = 0x43;
#ifdef CONFIG_TCC_BCHECK
        } else if (s == bounds_section || s == lbounds_section) {
            k = 0x44;
#endif
        } else if (s == rodata_section || 0 == strcmp(s->name, ".data.rel.ro")) {
            k = 0x45;
        } else if (s->sh_type == SHT_DYNAMIC) {
            k = 0x46;
        } else if (s == s1->got) {
            k = 0x47; /* .got as RELRO needs BIND_NOW in DT_FLAGS */
        } else {
            k = 0x50;
            if (s->sh_type == SHT_NOTE)
                k = 0x60;
            if (s->sh_flags & SHF_EXECINSTR)
                k = 0x70;
            if (s->sh_type == SHT_NOBITS)
                k = 0x80;
            if (s == interp)
                k = 0x00;
        }
        k += j;

        for (n = i; n > 1 && k < (f = sec_cls[n - 1]); --n)
            sec_cls[n] = f, sec_order[n] = sec_order[n - 1];
        sec_cls[n] = k, sec_order[n] = i;
    }
    sec_order[0] = 0;

    /* count PT_LOAD headers needed */
    n = f0 = 0;
    for (i = 1; i < nb_sections; i++) {
        s = s1->sections[sec_order[i]];
        k = sec_cls[i];
        f = 0;
        if (k < 0x700) {
            f = s->sh_flags & (SHF_ALLOC|SHF_WRITE|SHF_EXECINSTR|SHF_TLS);
#if TARGETOS_NetBSD
	    /* NetBSD only supports 2 PT_LOAD sections.
	       See: https://blog.netbsd.org/tnf/entry/the_first_report_on_lld */
	    if ((f & SHF_WRITE) == 0) f |= SHF_EXECINSTR;
#else
            if ((k & 0xfff0) == 0x240) /* RELRO sections */
                f |= 1<<4;
#endif
            if (f != f0) /* start new header when flags changed or relro */
                f0 = f, ++n, f |= 1<<8;
        }
        sec_cls[i] = f;
        //printf("ph %d sec %02d : %3X %3X  %8.2X  %04X  %s\n", !!f * n, i, f, k, s->sh_type, s->sh_size, s->name);
    }
    return n;
}

static ElfW(Phdr) *fill_phdr(ElfW(Phdr) *ph, int type, Section *s)
{
    if (s) {
        ph->p_offset = s->sh_offset;
        ph->p_vaddr = s->sh_addr;
        ph->p_filesz = s->sh_size;
        ph->p_align = s->sh_addralign;
    }
    ph->p_type = type;
    ph->p_flags = PF_R;
    ph->p_paddr = ph->p_vaddr;
    ph->p_memsz = ph->p_filesz;
    return ph;
}

/* Assign sections to segments and decide how are sections laid out when loaded
   in memory. This function also fills corresponding program headers. */
static int layout_sections(TCCState *s1, int *sec_order, struct dyn_inf *d)
{
    Section *s;
    addr_t addr, tmp, align, s_align, base;
    ElfW(Phdr) *ph = NULL;
    int i, f, n, phnum, phfill;
    int file_offset;

    /* compute number of program headers */
    phnum = sort_sections(s1, sec_order, d->interp);
    phfill = 0; /* set to 1 to have dll's with a PT_PHDR */
    if (d->interp)
        phfill = 2;
    phnum += phfill;
    if (d->note)
        ++phnum;
    if (d->dynamic)
        ++phnum;
    if (d->roinf)
        ++phnum;
    d->phnum = phnum;
    d->phdr = tcc_mallocz(phnum * sizeof(ElfW(Phdr)));

    file_offset = 0;
    if (s1->output_format == TCC_OUTPUT_FORMAT_ELF)
        file_offset = sizeof(ElfW(Ehdr)) + phnum * sizeof(ElfW(Phdr));

    s_align = ELF_PAGE_SIZE;
    if (s1->section_align)
        s_align = s1->section_align;

    addr = ELF_START_ADDR;
    if (s1->output_type & TCC_OUTPUT_DYN)
        addr = 0;

    if (s1->has_text_addr) {
        addr = s1->text_addr;
        if (0) {
            int a_offset, p_offset;
            /* we ensure that (addr % ELF_PAGE_SIZE) == file_offset %
               ELF_PAGE_SIZE */
            a_offset = (int) (addr & (s_align - 1));
            p_offset = file_offset & (s_align - 1);
            if (a_offset < p_offset)
                a_offset += s_align;
            file_offset += (a_offset - p_offset);
        }
    }
    base = addr;
    /* compute address after headers */
    addr = addr + (file_offset & (s_align - 1));

    n = 0;
    for(i = 1; i < s1->nb_sections; i++) {
        s = s1->sections[sec_order[i]];
        f = sec_order[i + s1->nb_sections];
        align = s->sh_addralign - 1;

        if (f == 0) { /* no alloc */
            file_offset = (file_offset + align) & ~align;
            s->sh_offset = file_offset;
            if (s->sh_type != SHT_NOBITS)
                file_offset += s->sh_size;
            continue;
        }

        if ((f & 1<<8) && n) {
            /* different rwx section flags */
            if (s1->output_format == TCC_OUTPUT_FORMAT_ELF) {
                /* if in the middle of a page, w e duplicate the page in
                   memory so that one copy is RX and the other is RW */
                if ((addr & (s_align - 1)) != 0)
                    addr += s_align;
            } else {
                align = s_align - 1;
            }
        }

        tmp = addr;
        addr = (addr + align) & ~align;
        file_offset += (int)(addr - tmp);
        s->sh_offset = file_offset;
        s->sh_addr = addr;

        if (f & 1<<8) {
            /* set new program header */
            ph = &d->phdr[phfill + n];
            ph->p_type = PT_LOAD;
            ph->p_align = s_align;
            ph->p_flags = PF_R;
            if (f & SHF_WRITE)
                ph->p_flags |= PF_W;
            if (f & SHF_EXECINSTR)
                ph->p_flags |= PF_X;
            if (f & SHF_TLS) {
                ph->p_type = PT_TLS;
                ph->p_align = 4;
            }
            ph->p_offset = file_offset;
            ph->p_vaddr = addr;
            if (n == 0) {
		/* Make the first PT_LOAD segment include the program
		   headers itself (and the ELF header as well), it'll
		   come out with same memory use but will make various
		   tools like binutils strip work better.  */
		ph->p_offset = 0;
		ph->p_vaddr = base;
            }
            ph->p_paddr = ph->p_vaddr;
            ++n;
        }

        if (f & 1<<4) {
            Section *roinf = &d->_roinf;
            if (roinf->sh_size == 0) {
                roinf->sh_offset = s->sh_offset;
                roinf->sh_addr = s->sh_addr;
                roinf->sh_addralign = 1;
	    }
            roinf->sh_size = (addr - roinf->sh_addr) + s->sh_size;
        }

        addr += s->sh_size;
        if (s->sh_type != SHT_NOBITS)
            file_offset += s->sh_size;

        ph->p_filesz = file_offset - ph->p_offset;
        ph->p_memsz = addr - ph->p_vaddr;
    }

    /* Fill other headers */
    if (d->note)
        fill_phdr(++ph, PT_NOTE, d->note);
    if (d->dynamic)
        fill_phdr(++ph, PT_DYNAMIC, d->dynamic)->p_flags |= PF_W;
    if (d->roinf)
        fill_phdr(++ph, PT_GNU_RELRO, d->roinf)->p_flags |= PF_W;
    if (d->interp)
        fill_phdr(&d->phdr[1], PT_INTERP, d->interp);
    if (phfill) {
        ph = &d->phdr[0];
        ph->p_offset = sizeof(ElfW(Ehdr));
        ph->p_vaddr = base + ph->p_offset;
        ph->p_filesz = phnum * sizeof(ElfW(Phdr));
        ph->p_align = 4;
        fill_phdr(ph, PT_PHDR, NULL);
    }
    return file_offset;
}

/* put dynamic tag */
static void put_dt(Section *dynamic, int dt, addr_t val)
{
    ElfW(Dyn) *dyn;
    dyn = section_ptr_add(dynamic, sizeof(ElfW(Dyn)));
    dyn->d_tag = dt;
    dyn->d_un.d_val = val;
}

/* Fill the dynamic section with tags describing the address and size of
   sections */
static void fill_dynamic(TCCState *s1, struct dyn_inf *dyninf)
{
    Section *dynamic = dyninf->dynamic;
    Section *s;

    /* put dynamic section entries */
    put_dt(dynamic, DT_HASH, s1->dynsym->hash->sh_addr);
    put_dt(dynamic, DT_GNU_HASH, dyninf->gnu_hash->sh_addr);
    put_dt(dynamic, DT_STRTAB, dyninf->dynstr->sh_addr);
    put_dt(dynamic, DT_SYMTAB, s1->dynsym->sh_addr);
    put_dt(dynamic, DT_STRSZ, dyninf->dynstr->data_offset);
    put_dt(dynamic, DT_SYMENT, sizeof(ElfW(Sym)));
#if PTR_SIZE == 8
    put_dt(dynamic, DT_RELA, dyninf->rel_addr);
    put_dt(dynamic, DT_RELASZ, dyninf->rel_size);
    put_dt(dynamic, DT_RELAENT, sizeof(ElfW_Rel));
    if (s1->plt && s1->plt->reloc) {
        put_dt(dynamic, DT_PLTGOT, s1->got->sh_addr);
        put_dt(dynamic, DT_PLTRELSZ, s1->plt->reloc->data_offset);
        put_dt(dynamic, DT_JMPREL, s1->plt->reloc->sh_addr);
        put_dt(dynamic, DT_PLTREL, DT_RELA);
    }
    put_dt(dynamic, DT_RELACOUNT, 0);
#else
    put_dt(dynamic, DT_REL, dyninf->rel_addr);
    put_dt(dynamic, DT_RELSZ, dyninf->rel_size);
    put_dt(dynamic, DT_RELENT, sizeof(ElfW_Rel));
    if (s1->plt && s1->plt->reloc) {
        put_dt(dynamic, DT_PLTGOT, s1->got->sh_addr);
        put_dt(dynamic, DT_PLTRELSZ, s1->plt->reloc->data_offset);
        put_dt(dynamic, DT_JMPREL, s1->plt->reloc->sh_addr);
        put_dt(dynamic, DT_PLTREL, DT_REL);
    }
    put_dt(dynamic, DT_RELCOUNT, 0);
#endif
    if (versym_section && verneed_section) {
	/* The dynamic linker can not handle VERSYM without VERNEED */
        put_dt(dynamic, DT_VERSYM, versym_section->sh_addr);
        put_dt(dynamic, DT_VERNEED, verneed_section->sh_addr);
        put_dt(dynamic, DT_VERNEEDNUM, dt_verneednum);
    }
    s = have_section(s1, ".preinit_array");
    if (s && s->data_offset) {
        put_dt(dynamic, DT_PREINIT_ARRAY, s->sh_addr);
        put_dt(dynamic, DT_PREINIT_ARRAYSZ, s->data_offset);
    }
    s = have_section(s1, ".init_array");
    if (s && s->data_offset) {
        put_dt(dynamic, DT_INIT_ARRAY, s->sh_addr);
        put_dt(dynamic, DT_INIT_ARRAYSZ, s->data_offset);
    }
    s = have_section(s1, ".fini_array");
    if (s && s->data_offset) {
        put_dt(dynamic, DT_FINI_ARRAY, s->sh_addr);
        put_dt(dynamic, DT_FINI_ARRAYSZ, s->data_offset);
    }
    s = have_section(s1, ".init");
    if (s && s->data_offset) {
        put_dt(dynamic, DT_INIT, s->sh_addr);
    }
    s = have_section(s1, ".fini");
    if (s && s->data_offset) {
        put_dt(dynamic, DT_FINI, s->sh_addr);
    }
    if (s1->do_debug)
        put_dt(dynamic, DT_DEBUG, 0);
    put_dt(dynamic, DT_NULL, 0);
}

/* Remove gaps between RELX sections.
   These gaps are a result of final_sections_reloc. Here some relocs are removed.
   The gaps are then filled with 0 in tcc_output_elf. The 0 is intepreted as
   R_...NONE reloc. This does work on most targets but on OpenBSD/arm64 this
   is illegal. OpenBSD/arm64 does not support R_...NONE reloc. */
static void update_reloc_sections(TCCState *s1, struct dyn_inf *dyninf)
{
    int i;
    unsigned long file_offset = 0;
    Section *s;
    Section *relocplt = s1->plt ? s1->plt->reloc : NULL;

    /* dynamic relocation table information, for .dynamic section */
    dyninf->rel_addr = dyninf->rel_size = 0;

    for(i = 1; i < s1->nb_sections; i++) {
        s = s1->sections[i];
	if (s->sh_type == SHT_RELX && s != relocplt) {
	    if (dyninf->rel_size == 0) {
		dyninf->rel_addr = s->sh_addr;
		file_offset = s->sh_offset;
	    }
	    else {
		s->sh_addr = dyninf->rel_addr + dyninf->rel_size;
		s->sh_offset = file_offset + dyninf->rel_size;
	    }
	    dyninf->rel_size += s->sh_size;
	}
    }
}

static int tidy_section_headers(TCCState *s1, int *sec_order);
#endif /* ndef ELF_OBJ_ONLY */

/* Create an ELF file on disk.
   This function handle ELF specific layout requirements */
static void tcc_output_elf(TCCState *s1, FILE *f, int phnum, ElfW(Phdr) *phdr,
                           int file_offset, int *sec_order)
{
    int i, shnum, offset, size, file_type;
    Section *s;
    ElfW(Ehdr) ehdr;
    ElfW(Shdr) shdr, *sh;

    file_type = s1->output_type;
    shnum = s1->nb_sections;

    memset(&ehdr, 0, sizeof(ehdr));

    if (phnum > 0) {
        ehdr.e_phentsize = sizeof(ElfW(Phdr));
        ehdr.e_phnum = phnum;
        ehdr.e_phoff = sizeof(ElfW(Ehdr));
#ifndef ELF_OBJ_ONLY
        shnum = tidy_section_headers(s1, sec_order);
#endif
    }

    /* align to 4 */
    file_offset = (file_offset + 3) & -4;

    /* fill header */
    ehdr.e_ident[0] = ELFMAG0;
    ehdr.e_ident[1] = ELFMAG1;
    ehdr.e_ident[2] = ELFMAG2;
    ehdr.e_ident[3] = ELFMAG3;
    ehdr.e_ident[4] = ELFCLASSW;
    ehdr.e_ident[5] = ELFDATA2LSB;
    ehdr.e_ident[6] = EV_CURRENT;

#if TARGETOS_FreeBSD || TARGETOS_FreeBSD_kernel
    ehdr.e_ident[EI_OSABI] = ELFOSABI_FREEBSD;
#elif defined TCC_TARGET_ARM && defined TCC_ARM_EABI
    ehdr.e_flags = EF_ARM_EABI_VER5;
    ehdr.e_flags |= s1->float_abi == ARM_HARD_FLOAT
        ? EF_ARM_VFP_FLOAT : EF_ARM_SOFT_FLOAT;
#elif defined TCC_TARGET_ARM
    ehdr.e_ident[EI_OSABI] = ELFOSABI_ARM;
#elif defined TCC_TARGET_RISCV64
    ehdr.e_flags = EF_RISCV_FLOAT_ABI_DOUBLE;
#endif

    if (file_type == TCC_OUTPUT_OBJ) {
        ehdr.e_type = ET_REL;
    } else {
        if (file_type & TCC_OUTPUT_DYN)
            ehdr.e_type = ET_DYN;
        else
            ehdr.e_type = ET_EXEC;
        if (s1->elf_entryname)
            ehdr.e_entry = get_sym_addr(s1, s1->elf_entryname, 1, 0);
        else
            ehdr.e_entry = get_sym_addr(s1, "_start", !!(file_type & TCC_OUTPUT_EXE), 0);
        if (ehdr.e_entry == (addr_t)-1)
            ehdr.e_entry = text_section->sh_addr;
    }

    ehdr.e_machine = EM_TCC_TARGET;
    ehdr.e_version = EV_CURRENT;
    ehdr.e_shoff = file_offset;
    ehdr.e_ehsize = sizeof(ElfW(Ehdr));
    ehdr.e_shentsize = sizeof(ElfW(Shdr));
    ehdr.e_shnum = shnum;
    ehdr.e_shstrndx = shnum - 1;

    fwrite(&ehdr, 1, sizeof(ElfW(Ehdr)), f);
    if (phdr)
        fwrite(phdr, 1, phnum * sizeof(ElfW(Phdr)), f);
    offset = sizeof(ElfW(Ehdr)) + phnum * sizeof(ElfW(Phdr));

    sort_syms(s1, symtab_section);

    for(i = 1; i < shnum; i++) {
        s = s1->sections[sec_order ? sec_order[i] : i];
        if (s->sh_type != SHT_NOBITS) {
            while (offset < s->sh_offset) {
                fputc(0, f);
                offset++;
            }
            size = s->sh_size;
            if (size)
                fwrite(s->data, 1, size, f);
            offset += size;
        }
    }

    /* output section headers */
    while (offset < ehdr.e_shoff) {
        fputc(0, f);
        offset++;
    }

    for(i = 0; i < shnum; i++) {
        sh = &shdr;
        memset(sh, 0, sizeof(ElfW(Shdr)));
        s = s1->sections[i];
        if (s) {
            sh->sh_name = s->sh_name;
            sh->sh_type = s->sh_type;
            sh->sh_flags = s->sh_flags;
            sh->sh_entsize = s->sh_entsize;
            sh->sh_info = s->sh_info;
            if (s->link)
                sh->sh_link = s->link->sh_num;
            sh->sh_addralign = s->sh_addralign;
            sh->sh_addr = s->sh_addr;
            sh->sh_offset = s->sh_offset;
            sh->sh_size = s->sh_size;
        }
        fwrite(sh, 1, sizeof(ElfW(Shdr)), f);
    }
}

static void tcc_output_binary(TCCState *s1, FILE *f,
                              const int *sec_order)
{
    Section *s;
    int i, offset, size;

    offset = 0;
    for(i=1;i<s1->nb_sections;i++) {
        s = s1->sections[sec_order[i]];
        if (s->sh_type != SHT_NOBITS &&
            (s->sh_flags & SHF_ALLOC)) {
            while (offset < s->sh_offset) {
                fputc(0, f);
                offset++;
            }
            size = s->sh_size;
            fwrite(s->data, 1, size, f);
            offset += size;
        }
    }
}

/* Write an elf, coff or "binary" file */
static int tcc_write_elf_file(TCCState *s1, const char *filename, int phnum,
                              ElfW(Phdr) *phdr, int file_offset, int *sec_order)
{
    int fd, mode, file_type;
    FILE *f;

    file_type = s1->output_type;
    if (file_type == TCC_OUTPUT_OBJ)
        mode = 0666;
    else
        mode = 0777;
    unlink(filename);
    fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY, mode);
    if (fd < 0 || (f = fdopen(fd, "wb")) == NULL) {
        tcc_error_noabort("could not write '%s: %s'", filename, strerror(errno));
        return -1;
    }
    if (s1->verbose)
        printf("<- %s\n", filename);

#ifdef TCC_TARGET_COFF
    if (s1->output_format == TCC_OUTPUT_FORMAT_COFF)
        tcc_output_coff(s1, f);
    else
#endif
    if (s1->output_format == TCC_OUTPUT_FORMAT_ELF)
        tcc_output_elf(s1, f, phnum, phdr, file_offset, sec_order);
    else
        tcc_output_binary(s1, f, sec_order);
    fclose(f);

    return 0;
}

#ifndef ELF_OBJ_ONLY
/* Sort section headers by assigned sh_addr, remove sections
   that we aren't going to output.  */
static int tidy_section_headers(TCCState *s1, int *sec_order)
{
    int i, nnew, l, *backmap;
    Section **snew, *s;
    ElfW(Sym) *sym;

    snew = tcc_malloc(s1->nb_sections * sizeof(snew[0]));
    backmap = tcc_malloc(s1->nb_sections * sizeof(backmap[0]));
    for (i = 0, nnew = 0, l = s1->nb_sections; i < s1->nb_sections; i++) {
	s = s1->sections[sec_order[i]];
	if (!i || s->sh_name) {
	    backmap[sec_order[i]] = nnew;
	    snew[nnew] = s;
	    ++nnew;
	} else {
	    backmap[sec_order[i]] = 0;
	    snew[--l] = s;
	}
    }
    for (i = 0; i < nnew; i++) {
	s = snew[i];
	if (s) {
	    s->sh_num = i;
            if (s->sh_type == SHT_RELX)
		s->sh_info = backmap[s->sh_info];
	}
    }

    for_each_elem(symtab_section, 1, sym, ElfW(Sym))
	if (sym->st_shndx != SHN_UNDEF && sym->st_shndx < SHN_LORESERVE)
	    sym->st_shndx = backmap[sym->st_shndx];
    if ( !s1->static_link ) {
        for_each_elem(s1->dynsym, 1, sym, ElfW(Sym))
	    if (sym->st_shndx != SHN_UNDEF && sym->st_shndx < SHN_LORESERVE)
	        sym->st_shndx = backmap[sym->st_shndx];
    }
    for (i = 0; i < s1->nb_sections; i++)
	sec_order[i] = i;
    tcc_free(s1->sections);
    s1->sections = snew;
    tcc_free(backmap);
    return nnew;
}

#ifdef TCC_TARGET_ARM
static void create_arm_attribute_section(TCCState *s1)
{
   // Needed for DLL support.
    static const unsigned char arm_attr[] = {
        0x41,                            // 'A'
        0x2c, 0x00, 0x00, 0x00,          // size 0x2c
        'a', 'e', 'a', 'b', 'i', 0x00,   // "aeabi"
        0x01, 0x22, 0x00, 0x00, 0x00,    // 'File Attributes', size 0x22
        0x05, 0x36, 0x00,                // 'CPU_name', "6"
        0x06, 0x06,                      // 'CPU_arch', 'v6'
        0x08, 0x01,                      // 'ARM_ISA_use', 'Yes'
        0x09, 0x01,                      // 'THUMB_ISA_use', 'Thumb-1'
        0x0a, 0x02,                      // 'FP_arch', 'VFPv2'
        0x12, 0x04,                      // 'ABI_PCS_wchar_t', 4
        0x14, 0x01,                      // 'ABI_FP_denormal', 'Needed'
        0x15, 0x01,                      // 'ABI_FP_exceptions', 'Needed'
        0x17, 0x03,                      // 'ABI_FP_number_model', 'IEEE 754'
        0x18, 0x01,                      // 'ABI_align_needed', '8-byte'
        0x19, 0x01,                      // 'ABI_align_preserved', '8-byte, except leaf SP'
        0x1a, 0x02,                      // 'ABI_enum_size', 'int'
        0x1c, 0x01,                      // 'ABI_VFP_args', 'VFP registers'
        0x22, 0x01                       // 'CPU_unaligned_access', 'v6'
    };
    Section *attr = new_section(s1, ".ARM.attributes", SHT_ARM_ATTRIBUTES, 0);
    unsigned char *ptr = section_ptr_add(attr, sizeof(arm_attr));
    attr->sh_addralign = 1;
    memcpy(ptr, arm_attr, sizeof(arm_attr));
    if (s1->float_abi != ARM_HARD_FLOAT) {
        ptr[26] = 0x00; // 'FP_arch', 'No'
        ptr[41] = 0x1e; // 'ABI_optimization_goals'
        ptr[42] = 0x06; // 'Aggressive Debug'
    }
}
#endif

#if TARGETOS_OpenBSD || TARGETOS_NetBSD
static Section *create_bsd_note_section(TCCState *s1,
					const char *name,
					const char *value)
{
    Section *s = find_section (s1, name);

    if (s->data_offset == 0) {
        char *ptr = section_ptr_add(s, sizeof(ElfW(Nhdr)) + 8 + 4);
        ElfW(Nhdr) *note = (ElfW(Nhdr) *) ptr;

        s->sh_type = SHT_NOTE;
        note->n_namesz = 8;
        note->n_descsz = 4;
        note->n_type = ELF_NOTE_OS_GNU;
	strcpy (ptr + sizeof(ElfW(Nhdr)), value);
    }
    return s;
}
#endif

static void alloc_sec_names(TCCState *s1, int is_obj);

/* Output an elf, coff or binary file */
/* XXX: suppress unneeded sections */
static int elf_output_file(TCCState *s1, const char *filename)
{
    int i, ret, file_type, file_offset, *sec_order;
    struct dyn_inf dyninf = {0};
    Section *interp, *dynstr, *dynamic;
    int textrel, got_sym, dt_flags_1;

    file_type = s1->output_type;
    s1->nb_errors = 0;
    ret = -1;
    interp = dynstr = dynamic = NULL;
    sec_order = NULL;
    dyninf.roinf = &dyninf._roinf;

#ifdef TCC_TARGET_ARM
    create_arm_attribute_section (s1);
#endif

#if TARGETOS_OpenBSD
    dyninf.note = create_bsd_note_section (s1, ".note.openbsd.ident", "OpenBSD");
#endif

#if TARGETOS_NetBSD
    dyninf.note = create_bsd_note_section (s1, ".note.netbsd.ident", "NetBSD");
#endif

#if TARGETOS_FreeBSD || TARGETOS_NetBSD
    dyninf.roinf = NULL;
#endif
        /* if linking, also link in runtime libraries (libc, libgcc, etc.) */
        tcc_add_runtime(s1);
	resolve_common_syms(s1);

        if (!s1->static_link) {
            if (file_type & TCC_OUTPUT_EXE) {
                char *ptr;
                /* allow override the dynamic loader */
                const char *elfint = getenv("LD_SO");
                if (elfint == NULL)
                    elfint = DEFAULT_ELFINTERP(s1);
                /* add interpreter section only if executable */
                interp = new_section(s1, ".interp", SHT_PROGBITS, SHF_ALLOC);
                interp->sh_addralign = 1;
                ptr = section_ptr_add(interp, 1 + strlen(elfint));
                strcpy(ptr, elfint);
                dyninf.interp = interp;
            }

            /* add dynamic symbol table */
            s1->dynsym = new_symtab(s1, ".dynsym", SHT_DYNSYM, SHF_ALLOC,
                                    ".dynstr",
                                    ".hash", SHF_ALLOC);
	    /* Number of local symbols (readelf complains if not set) */
	    s1->dynsym->sh_info = 1;
            dynstr = s1->dynsym->link;
            /* add dynamic section */
            dynamic = new_section(s1, ".dynamic", SHT_DYNAMIC,
                                  SHF_ALLOC | SHF_WRITE);
            dynamic->link = dynstr;
            dynamic->sh_entsize = sizeof(ElfW(Dyn));

            got_sym = build_got(s1);
            if (file_type == TCC_OUTPUT_EXE) {
                bind_exe_dynsyms(s1);
                if (s1->nb_errors)
                    goto the_end;
            }
            build_got_entries(s1, got_sym);
            if (file_type & TCC_OUTPUT_EXE) {
                bind_libs_dynsyms(s1);
            } else {
                /* shared library case: simply export all global symbols */
                export_global_syms(s1);
            }
	    dyninf.gnu_hash = create_gnu_hash(s1);
        } else {
            build_got_entries(s1, 0);
        }
	version_add (s1);

    textrel = set_sec_sizes(s1);
    alloc_sec_names(s1, 0);

    if (!s1->static_link) {
        /* add a list of needed dlls */
        for(i = 0; i < s1->nb_loaded_dlls; i++) {
            DLLReference *dllref = s1->loaded_dlls[i];
            if (dllref->level == 0)
                put_dt(dynamic, DT_NEEDED, put_elf_str(dynstr, dllref->name));
        }

        if (s1->rpath)
            put_dt(dynamic, s1->enable_new_dtags ? DT_RUNPATH : DT_RPATH,
                   put_elf_str(dynstr, s1->rpath));

        dt_flags_1 = DF_1_NOW;
        if (file_type & TCC_OUTPUT_DYN) {
            if (s1->soname)
                put_dt(dynamic, DT_SONAME, put_elf_str(dynstr, s1->soname));
            /* XXX: currently, since we do not handle PIC code, we
               must relocate the readonly segments */
            if (textrel)
                put_dt(dynamic, DT_TEXTREL, 0);
            if (file_type & TCC_OUTPUT_EXE)
                dt_flags_1 = DF_1_NOW | DF_1_PIE;
        }
        put_dt(dynamic, DT_FLAGS, DF_BIND_NOW);
        put_dt(dynamic, DT_FLAGS_1, dt_flags_1);
        if (s1->symbolic)
            put_dt(dynamic, DT_SYMBOLIC, 0);

        dyninf.dynamic = dynamic;
        dyninf.dynstr = dynstr;
        /* remember offset and reserve space for 2nd call below */
        dyninf.data_offset = dynamic->data_offset;
        fill_dynamic(s1, &dyninf);
        dynamic->sh_size = dynamic->data_offset;
        dynstr->sh_size = dynstr->data_offset;
    }

    /* this array is used to reorder sections in the output file */
    sec_order = tcc_malloc(sizeof(int) * 2 * s1->nb_sections);
    /* compute section to program header mapping */
    file_offset = layout_sections(s1, sec_order, &dyninf);

        if (dynamic) {
            /* put in GOT the dynamic section address and relocate PLT */
            write32le(s1->got->data, dynamic->sh_addr);
            if (file_type == TCC_OUTPUT_EXE
                || (RELOCATE_DLLPLT && (file_type & TCC_OUTPUT_DYN)))
                relocate_plt(s1);
            /* relocate symbols in .dynsym now that final addresses are known */
            relocate_syms(s1, s1->dynsym, 2);
        }

        /* if building executable or DLL, then relocate each section
           except the GOT which is already relocated */
        relocate_syms(s1, s1->symtab, 0);
        if (s1->nb_errors != 0)
            goto the_end;
        relocate_sections(s1);
        if (dynamic) {
	    update_reloc_sections (s1, &dyninf);
            dynamic->data_offset = dyninf.data_offset;
            fill_dynamic(s1, &dyninf);
	}
        /* Perform relocation to GOT or PLT entries */
        if (file_type == TCC_OUTPUT_EXE && s1->static_link)
            fill_got(s1);
        else if (s1->got)
            fill_local_got_entries(s1);

    if (dyninf.gnu_hash)
        update_gnu_hash(s1, dyninf.gnu_hash);

    /* Create the ELF file with name 'filename' */
    ret = tcc_write_elf_file(s1, filename, dyninf.phnum, dyninf.phdr, file_offset, sec_order);
 the_end:
    tcc_free(sec_order);
    tcc_free(dyninf.phdr);
    return ret;
}
#endif /* ndef ELF_OBJ_ONLY */

/* Allocate strings for section names */
static void alloc_sec_names(TCCState *s1, int is_obj)
{
    int i;
    Section *s, *strsec;

    strsec = new_section(s1, ".shstrtab", SHT_STRTAB, 0);
    put_elf_str(strsec, "");
    for(i = 1; i < s1->nb_sections; i++) {
        s = s1->sections[i];
        if (is_obj)
            s->sh_size = s->data_offset;
	if (s == strsec || s->sh_size || (s->sh_flags & SHF_ALLOC))
            s->sh_name = put_elf_str(strsec, s->name);
    }
    strsec->sh_size = strsec->data_offset;
}

/* Output an elf .o file */
static int elf_output_obj(TCCState *s1, const char *filename)
{
    Section *s;
    int i, ret, file_offset;
    s1->nb_errors = 0;
    /* Allocate strings for section names */
    alloc_sec_names(s1, 1);
    file_offset = sizeof (ElfW(Ehdr));
    for(i = 1; i < s1->nb_sections; i++) {
        s = s1->sections[i];
        file_offset = (file_offset + 15) & -16;
        s->sh_offset = file_offset;
        if (s->sh_type != SHT_NOBITS)
            file_offset += s->sh_size;
    }
    /* Create the ELF file with name 'filename' */
    ret = tcc_write_elf_file(s1, filename, 0, NULL, file_offset, NULL);
    return ret;
}

LIBTCCAPI int tcc_output_file(TCCState *s, const char *filename)
{
    if (s->test_coverage)
        tcc_tcov_add_file(s, filename);
    if (s->output_type == TCC_OUTPUT_OBJ)
        return elf_output_obj(s, filename);
#ifdef TCC_TARGET_PE
    return  pe_output_file(s, filename);
#elif TCC_TARGET_MACHO
    return macho_output_file(s, filename);
#else
    return elf_output_file(s, filename);
#endif
}

ST_FUNC ssize_t full_read(int fd, void *buf, size_t count) {
    char *cbuf = buf;
    size_t rnum = 0;
    while (1) {
        ssize_t num = read(fd, cbuf, count-rnum);
        if (num < 0) return num;
        if (num == 0) return rnum;
        rnum += num;
        cbuf += num;
    }
}

ST_FUNC void *load_data(int fd, unsigned long file_offset, unsigned long size)
{
    void *data;

    data = tcc_malloc(size);
    lseek(fd, file_offset, SEEK_SET);
    full_read(fd, data, size);
    return data;
}

typedef struct SectionMergeInfo {
    Section *s;            /* corresponding existing section */
    unsigned long offset;  /* offset of the new section in the existing section */
    uint8_t new_section;       /* true if section 's' was added */
    uint8_t link_once;         /* true if link once section */
} SectionMergeInfo;

ST_FUNC int tcc_object_type(int fd, ElfW(Ehdr) *h)
{
    int size = full_read(fd, h, sizeof *h);
    if (size == sizeof *h && 0 == memcmp(h, ELFMAG, 4)) {
        if (h->e_type == ET_REL)
            return AFF_BINTYPE_REL;
        if (h->e_type == ET_DYN)
            return AFF_BINTYPE_DYN;
    } else if (size >= 8) {
        if (0 == memcmp(h, ARMAG, 8))
            return AFF_BINTYPE_AR;
#ifdef TCC_TARGET_COFF
        if (((struct filehdr*)h)->f_magic == COFF_C67_MAGIC)
            return AFF_BINTYPE_C67;
#endif
    }
    return 0;
}

/* load an object file and merge it with current files */
/* XXX: handle correctly stab (debug) info */
ST_FUNC int tcc_load_object_file(TCCState *s1,
                                int fd, unsigned long file_offset)
{
    ElfW(Ehdr) ehdr;
    ElfW(Shdr) *shdr, *sh;
    int size, i, j, offset, offseti, nb_syms, sym_index, ret, seencompressed;
    char *strsec, *strtab;
    int stab_index, stabstr_index;
    int *old_to_new_syms;
    char *sh_name, *name;
    SectionMergeInfo *sm_table, *sm;
    ElfW(Sym) *sym, *symtab;
    ElfW_Rel *rel;
    Section *s;

    lseek(fd, file_offset, SEEK_SET);
    if (tcc_object_type(fd, &ehdr) != AFF_BINTYPE_REL)
        goto fail1;
    /* test CPU specific stuff */
    if (ehdr.e_ident[5] != ELFDATA2LSB ||
        ehdr.e_machine != EM_TCC_TARGET) {
    fail1:
        tcc_error_noabort("invalid object file");
        return -1;
    }
    /* read sections */
    shdr = load_data(fd, file_offset + ehdr.e_shoff,
                     sizeof(ElfW(Shdr)) * ehdr.e_shnum);
    sm_table = tcc_mallocz(sizeof(SectionMergeInfo) * ehdr.e_shnum);

    /* load section names */
    sh = &shdr[ehdr.e_shstrndx];
    strsec = load_data(fd, file_offset + sh->sh_offset, sh->sh_size);

    /* load symtab and strtab */
    old_to_new_syms = NULL;
    symtab = NULL;
    strtab = NULL;
    nb_syms = 0;
    seencompressed = 0;
    stab_index = stabstr_index = 0;

    for(i = 1; i < ehdr.e_shnum; i++) {
        sh = &shdr[i];
        if (sh->sh_type == SHT_SYMTAB) {
            if (symtab) {
                tcc_error_noabort("object must contain only one symtab");
            fail:
                ret = -1;
                goto the_end;
            }
            nb_syms = sh->sh_size / sizeof(ElfW(Sym));
            symtab = load_data(fd, file_offset + sh->sh_offset, sh->sh_size);
            sm_table[i].s = symtab_section;

            /* now load strtab */
            sh = &shdr[sh->sh_link];
            strtab = load_data(fd, file_offset + sh->sh_offset, sh->sh_size);
        }
	if (sh->sh_flags & SHF_COMPRESSED)
	    seencompressed = 1;
    }

    /* now examine each section and try to merge its content with the
       ones in memory */
    for(i = 1; i < ehdr.e_shnum; i++) {
        /* no need to examine section name strtab */
        if (i == ehdr.e_shstrndx)
            continue;
        sh = &shdr[i];
	if (sh->sh_type == SHT_RELX)
	  sh = &shdr[sh->sh_info];
        /* ignore sections types we do not handle (plus relocs to those) */
        if (sh->sh_type != SHT_PROGBITS &&
#ifdef TCC_ARM_EABI
            sh->sh_type != SHT_ARM_EXIDX &&
#endif
#if TARGETOS_OpenBSD || TARGETOS_FreeBSD || TARGETOS_NetBSD
            sh->sh_type != SHT_X86_64_UNWIND &&
#endif
            sh->sh_type != SHT_NOTE &&
            sh->sh_type != SHT_NOBITS &&
            sh->sh_type != SHT_PREINIT_ARRAY &&
            sh->sh_type != SHT_INIT_ARRAY &&
            sh->sh_type != SHT_FINI_ARRAY &&
            strcmp(strsec + sh->sh_name, ".stabstr")
            )
            continue;
	if (seencompressed && 0 == strncmp(strsec + sh->sh_name, ".debug_", 7))
	  continue;

	sh = &shdr[i];
        sh_name = strsec + sh->sh_name;
        if (sh->sh_addralign < 1)
            sh->sh_addralign = 1;
        /* find corresponding section, if any */
        for(j = 1; j < s1->nb_sections;j++) {
            s = s1->sections[j];
            if (!strcmp(s->name, sh_name)) {
                if (!strncmp(sh_name, ".gnu.linkonce",
                             sizeof(".gnu.linkonce") - 1)) {
                    /* if a 'linkonce' section is already present, we
                       do not add it again. It is a little tricky as
                       symbols can still be defined in
                       it. */
                    sm_table[i].link_once = 1;
                    goto next;
                }
                if (stab_section) {
                    if (s == stab_section)
                        stab_index = i;
                    if (s == stab_section->link)
                        stabstr_index = i;
                }
                goto found;
            }
        }
        /* not found: create new section */
        s = new_section(s1, sh_name, sh->sh_type, sh->sh_flags & ~SHF_GROUP);
        /* take as much info as possible from the section. sh_link and
           sh_info will be updated later */
        s->sh_addralign = sh->sh_addralign;
        s->sh_entsize = sh->sh_entsize;
        sm_table[i].new_section = 1;
    found:
        if (sh->sh_type != s->sh_type) {
#if TARGETOS_OpenBSD || TARGETOS_FreeBSD || TARGETOS_NetBSD
            if (strcmp (s->name, ".eh_frame"))
#endif
            {
                tcc_error_noabort("invalid section type");
                goto fail;
	    }
        }
        /* align start of section */
        s->data_offset += -s->data_offset & (sh->sh_addralign - 1);
        if (sh->sh_addralign > s->sh_addralign)
            s->sh_addralign = sh->sh_addralign;
        sm_table[i].offset = s->data_offset;
        sm_table[i].s = s;
        /* concatenate sections */
        size = sh->sh_size;
        if (sh->sh_type != SHT_NOBITS) {
            unsigned char *ptr;
            lseek(fd, file_offset + sh->sh_offset, SEEK_SET);
            ptr = section_ptr_add(s, size);
            full_read(fd, ptr, size);
        } else {
            s->data_offset += size;
        }
    next: ;
    }

    /* gr relocate stab strings */
    if (stab_index && stabstr_index) {
        Stab_Sym *a, *b;
        unsigned o;
        s = sm_table[stab_index].s;
        a = (Stab_Sym *)(s->data + sm_table[stab_index].offset);
        b = (Stab_Sym *)(s->data + s->data_offset);
        o = sm_table[stabstr_index].offset;
        while (a < b) {
            if (a->n_strx)
                a->n_strx += o;
            a++;
        }
    }

    /* second short pass to update sh_link and sh_info fields of new
       sections */
    for(i = 1; i < ehdr.e_shnum; i++) {
        s = sm_table[i].s;
        if (!s || !sm_table[i].new_section)
            continue;
        sh = &shdr[i];
        if (sh->sh_link > 0)
            s->link = sm_table[sh->sh_link].s;
        if (sh->sh_type == SHT_RELX) {
            s->sh_info = sm_table[sh->sh_info].s->sh_num;
            /* update backward link */
            s1->sections[s->sh_info]->reloc = s;
        }
    }

    /* resolve symbols */
    old_to_new_syms = tcc_mallocz(nb_syms * sizeof(int));

    sym = symtab + 1;
    for(i = 1; i < nb_syms; i++, sym++) {
        if (sym->st_shndx != SHN_UNDEF &&
            sym->st_shndx < SHN_LORESERVE) {
            sm = &sm_table[sym->st_shndx];
            if (sm->link_once) {
                /* if a symbol is in a link once section, we use the
                   already defined symbol. It is very important to get
                   correct relocations */
                if (ELFW(ST_BIND)(sym->st_info) != STB_LOCAL) {
                    name = strtab + sym->st_name;
                    sym_index = find_elf_sym(symtab_section, name);
                    if (sym_index)
                        old_to_new_syms[i] = sym_index;
                }
                continue;
            }
            /* if no corresponding section added, no need to add symbol */
            if (!sm->s)
                continue;
            /* convert section number */
            sym->st_shndx = sm->s->sh_num;
            /* offset value */
            sym->st_value += sm->offset;
        }
        /* add symbol */
        name = strtab + sym->st_name;
        sym_index = set_elf_sym(symtab_section, sym->st_value, sym->st_size,
                                sym->st_info, sym->st_other,
                                sym->st_shndx, name);
        old_to_new_syms[i] = sym_index;
    }

    /* third pass to patch relocation entries */
    for(i = 1; i < ehdr.e_shnum; i++) {
        s = sm_table[i].s;
        if (!s)
            continue;
        sh = &shdr[i];
        offset = sm_table[i].offset;
        size = sh->sh_size;
        switch(s->sh_type) {
        case SHT_RELX:
            /* take relocation offset information */
            offseti = sm_table[sh->sh_info].offset;
	    for (rel = (ElfW_Rel *) s->data + (offset / sizeof(*rel));
		 rel < (ElfW_Rel *) s->data + ((offset + size) / sizeof(*rel));
		 rel++) {
                int type;
                unsigned sym_index;
                /* convert symbol index */
                type = ELFW(R_TYPE)(rel->r_info);
                sym_index = ELFW(R_SYM)(rel->r_info);
                /* NOTE: only one symtab assumed */
                if (sym_index >= nb_syms)
                    goto invalid_reloc;
                sym_index = old_to_new_syms[sym_index];
                /* ignore link_once in rel section. */
                if (!sym_index && !sm_table[sh->sh_info].link_once
#ifdef TCC_TARGET_ARM
                    && type != R_ARM_V4BX
#elif defined TCC_TARGET_RISCV64
                    && type != R_RISCV_ALIGN
                    && type != R_RISCV_RELAX
#endif
                   ) {
                invalid_reloc:
                    tcc_error_noabort("Invalid relocation entry [%2d] '%s' @ %.8x",
                        i, strsec + sh->sh_name, (int)rel->r_offset);
                    goto fail;
                }
                rel->r_info = ELFW(R_INFO)(sym_index, type);
                /* offset the relocation offset */
                rel->r_offset += offseti;
#ifdef TCC_TARGET_ARM
                /* Jumps and branches from a Thumb code to a PLT entry need
                   special handling since PLT entries are ARM code.
                   Unconditional bl instructions referencing PLT entries are
                   handled by converting these instructions into blx
                   instructions. Other case of instructions referencing a PLT
                   entry require to add a Thumb stub before the PLT entry to
                   switch to ARM mode. We set bit plt_thumb_stub of the
                   attribute of a symbol to indicate such a case. */
                if (type == R_ARM_THM_JUMP24)
                    get_sym_attr(s1, sym_index, 1)->plt_thumb_stub = 1;
#endif
            }
            break;
        default:
            break;
        }
    }

    ret = 0;
 the_end:
    tcc_free(symtab);
    tcc_free(strtab);
    tcc_free(old_to_new_syms);
    tcc_free(sm_table);
    tcc_free(strsec);
    tcc_free(shdr);
    return ret;
}

typedef struct ArchiveHeader {
    char ar_name[16];           /* name of this member */
    char ar_date[12];           /* file mtime */
    char ar_uid[6];             /* owner uid; printed as decimal */
    char ar_gid[6];             /* owner gid; printed as decimal */
    char ar_mode[8];            /* file mode, printed as octal   */
    char ar_size[10];           /* file size, printed as decimal */
    char ar_fmag[2];            /* should contain ARFMAG */
} ArchiveHeader;

#define ARFMAG "`\n"

static unsigned long long get_be(const uint8_t *b, int n)
{
    unsigned long long ret = 0;
    while (n)
        ret = (ret << 8) | *b++, --n;
    return ret;
}

static int read_ar_header(int fd, int offset, ArchiveHeader *hdr)
{
    char *p, *e;
    int len;
    lseek(fd, offset, SEEK_SET);
    len = full_read(fd, hdr, sizeof(ArchiveHeader));
    if (len != sizeof(ArchiveHeader))
        return len ? -1 : 0;
    p = hdr->ar_name;
    for (e = p + sizeof hdr->ar_name; e > p && e[-1] == ' ';)
        --e;
    *e = '\0';
    hdr->ar_size[sizeof hdr->ar_size-1] = 0;
    return len;
}

/* load only the objects which resolve undefined symbols */
static int tcc_load_alacarte(TCCState *s1, int fd, int size, int entrysize)
{
    int i, bound, nsyms, sym_index, len, ret = -1;
    unsigned long long off;
    uint8_t *data;
    const char *ar_names, *p;
    const uint8_t *ar_index;
    ElfW(Sym) *sym;
    ArchiveHeader hdr;

    data = tcc_malloc(size);
    if (full_read(fd, data, size) != size)
        goto the_end;
    nsyms = get_be(data, entrysize);
    ar_index = data + entrysize;
    ar_names = (char *) ar_index + nsyms * entrysize;

    do {
        bound = 0;
        for (p = ar_names, i = 0; i < nsyms; i++, p += strlen(p)+1) {
            Section *s = symtab_section;
            sym_index = find_elf_sym(s, p);
            if (!sym_index)
                continue;
            sym = &((ElfW(Sym) *)s->data)[sym_index];
            if(sym->st_shndx != SHN_UNDEF)
                continue;
            off = get_be(ar_index + i * entrysize, entrysize);
            len = read_ar_header(fd, off, &hdr);
            if (len <= 0 || memcmp(hdr.ar_fmag, ARFMAG, 2)) {
                tcc_error_noabort("invalid archive");
                goto the_end;
            }
            off += len;
            if (s1->verbose == 2)
                printf("   -> %s\n", hdr.ar_name);
            if (tcc_load_object_file(s1, fd, off) < 0)
                goto the_end;
            ++bound;
        }
    } while(bound);
    ret = 0;
 the_end:
    tcc_free(data);
    return ret;
}

/* load a '.a' file */
ST_FUNC int tcc_load_archive(TCCState *s1, int fd, int alacarte)
{
    ArchiveHeader hdr;
    /* char magic[8]; */
    int size, len;
    unsigned long file_offset;
    ElfW(Ehdr) ehdr;

    /* skip magic which was already checked */
    /* full_read(fd, magic, sizeof(magic)); */
    file_offset = sizeof ARMAG - 1;

    for(;;) {
        len = read_ar_header(fd, file_offset, &hdr);
        if (len == 0)
            return 0;
        if (len < 0) {
            tcc_error_noabort("invalid archive");
            return -1;
        }
        file_offset += len;
        size = strtol(hdr.ar_size, NULL, 0);
        /* align to even */
        size = (size + 1) & ~1;
        if (alacarte) {
            /* coff symbol table : we handle it */
            if (!strcmp(hdr.ar_name, "/"))
                return tcc_load_alacarte(s1, fd, size, 4);
            if (!strcmp(hdr.ar_name, "/SYM64/"))
                return tcc_load_alacarte(s1, fd, size, 8);
        } else if (tcc_object_type(fd, &ehdr) == AFF_BINTYPE_REL) {
            if (s1->verbose == 2)
                printf("   -> %s\n", hdr.ar_name);
            if (tcc_load_object_file(s1, fd, file_offset) < 0)
                return -1;
        }
        file_offset += size;
    }
}

#ifndef ELF_OBJ_ONLY
/* Set LV[I] to the global index of sym-version (LIB,VERSION).  Maybe resizes
   LV, maybe create a new entry for (LIB,VERSION).  */
static void set_ver_to_ver(TCCState *s1, int *n, int **lv, int i, char *lib, char *version)
{
    while (i >= *n) {
        *lv = tcc_realloc(*lv, (*n + 1) * sizeof(**lv));
        (*lv)[(*n)++] = -1;
    }
    if ((*lv)[i] == -1) {
        int v, prev_same_lib = -1;
        for (v = 0; v < nb_sym_versions; v++) {
            if (strcmp(sym_versions[v].lib, lib))
              continue;
            prev_same_lib = v;
            if (!strcmp(sym_versions[v].version, version))
              break;
        }
        if (v == nb_sym_versions) {
            sym_versions = tcc_realloc (sym_versions,
                                        (v + 1) * sizeof(*sym_versions));
            sym_versions[v].lib = tcc_strdup(lib);
            sym_versions[v].version = tcc_strdup(version);
            sym_versions[v].out_index = 0;
            sym_versions[v].prev_same_lib = prev_same_lib;
            nb_sym_versions++;
        }
        (*lv)[i] = v;
    }
}

/* Associates symbol SYM_INDEX (in dynsymtab) with sym-version index
   VERNDX.  */
static void
set_sym_version(TCCState *s1, int sym_index, int verndx)
{
    if (sym_index >= nb_sym_to_version) {
        int newelems = sym_index ? sym_index * 2 : 1;
        sym_to_version = tcc_realloc(sym_to_version,
                                     newelems * sizeof(*sym_to_version));
        memset(sym_to_version + nb_sym_to_version, -1,
               (newelems - nb_sym_to_version) * sizeof(*sym_to_version));
        nb_sym_to_version = newelems;
    }
    if (sym_to_version[sym_index] < 0)
      sym_to_version[sym_index] = verndx;
}

struct versym_info {
    int nb_versyms;
    ElfW(Verdef) *verdef;
    ElfW(Verneed) *verneed;
    ElfW(Half) *versym;
    int nb_local_ver, *local_ver;
};


static void store_version(TCCState *s1, struct versym_info *v, char *dynstr)
{
    char *lib, *version;
    uint32_t next;
    int i;

#define	DEBUG_VERSION 0

    if (v->versym && v->verdef) {
      ElfW(Verdef) *vdef = v->verdef;
      lib = NULL;
      do {
        ElfW(Verdaux) *verdaux =
	  (ElfW(Verdaux) *) (((char *) vdef) + vdef->vd_aux);

#if DEBUG_VERSION
	printf ("verdef: version:%u flags:%u index:%u, hash:%u\n",
	        vdef->vd_version, vdef->vd_flags, vdef->vd_ndx,
		vdef->vd_hash);
#endif
	if (vdef->vd_cnt) {
          version = dynstr + verdaux->vda_name;

	  if (lib == NULL)
	    lib = version;
	  else
            set_ver_to_ver(s1, &v->nb_local_ver, &v->local_ver, vdef->vd_ndx,
                           lib, version);
#if DEBUG_VERSION
	  printf ("  verdaux(%u): %s\n", vdef->vd_ndx, version);
#endif
	}
        next = vdef->vd_next;
        vdef = (ElfW(Verdef) *) (((char *) vdef) + next);
      } while (next);
    }
    if (v->versym && v->verneed) {
      ElfW(Verneed) *vneed = v->verneed;
      do {
        ElfW(Vernaux) *vernaux =
	  (ElfW(Vernaux) *) (((char *) vneed) + vneed->vn_aux);

        lib = dynstr + vneed->vn_file;
#if DEBUG_VERSION
	printf ("verneed: %u %s\n", vneed->vn_version, lib);
#endif
	for (i = 0; i < vneed->vn_cnt; i++) {
	  if ((vernaux->vna_other & 0x8000) == 0) { /* hidden */
              version = dynstr + vernaux->vna_name;
              set_ver_to_ver(s1, &v->nb_local_ver, &v->local_ver, vernaux->vna_other,
                             lib, version);
#if DEBUG_VERSION
	    printf ("  vernaux(%u): %u %u %s\n",
		    vernaux->vna_other, vernaux->vna_hash,
		    vernaux->vna_flags, version);
#endif
	  }
	  vernaux = (ElfW(Vernaux) *) (((char *) vernaux) + vernaux->vna_next);
	}
        next = vneed->vn_next;
        vneed = (ElfW(Verneed) *) (((char *) vneed) + next);
      } while (next);
    }

#if DEBUG_VERSION
    for (i = 0; i < v->nb_local_ver; i++) {
      if (v->local_ver[i] > 0) {
        printf ("%d: lib: %s, version %s\n",
		i, sym_versions[v->local_ver[i]].lib,
                sym_versions[v->local_ver[i]].version);
      }
    }
#endif
}

/* load a DLL and all referenced DLLs. 'level = 0' means that the DLL
   is referenced by the user (so it should be added as DT_NEEDED in
   the generated ELF file) */
ST_FUNC int tcc_load_dll(TCCState *s1, int fd, const char *filename, int level)
{
    ElfW(Ehdr) ehdr;
    ElfW(Shdr) *shdr, *sh, *sh1;
    int i, nb_syms, nb_dts, sym_bind, ret = -1;
    ElfW(Sym) *sym, *dynsym;
    ElfW(Dyn) *dt, *dynamic;

    char *dynstr;
    int sym_index;
    const char *name, *soname;
    struct versym_info v;

    full_read(fd, &ehdr, sizeof(ehdr));

    /* test CPU specific stuff */
    if (ehdr.e_ident[5] != ELFDATA2LSB ||
        ehdr.e_machine != EM_TCC_TARGET) {
        tcc_error_noabort("bad architecture");
        return -1;
    }

    /* read sections */
    shdr = load_data(fd, ehdr.e_shoff, sizeof(ElfW(Shdr)) * ehdr.e_shnum);

    /* load dynamic section and dynamic symbols */
    nb_syms = 0;
    nb_dts = 0;
    dynamic = NULL;
    dynsym = NULL; /* avoid warning */
    dynstr = NULL; /* avoid warning */
    memset(&v, 0, sizeof v);

    for(i = 0, sh = shdr; i < ehdr.e_shnum; i++, sh++) {
        switch(sh->sh_type) {
        case SHT_DYNAMIC:
            nb_dts = sh->sh_size / sizeof(ElfW(Dyn));
            dynamic = load_data(fd, sh->sh_offset, sh->sh_size);
            break;
        case SHT_DYNSYM:
            nb_syms = sh->sh_size / sizeof(ElfW(Sym));
            dynsym = load_data(fd, sh->sh_offset, sh->sh_size);
            sh1 = &shdr[sh->sh_link];
            dynstr = load_data(fd, sh1->sh_offset, sh1->sh_size);
            break;
        case SHT_GNU_verdef:
	    v.verdef = load_data(fd, sh->sh_offset, sh->sh_size);
	    break;
        case SHT_GNU_verneed:
	    v.verneed = load_data(fd, sh->sh_offset, sh->sh_size);
	    break;
        case SHT_GNU_versym:
            v.nb_versyms = sh->sh_size / sizeof(ElfW(Half));
	    v.versym = load_data(fd, sh->sh_offset, sh->sh_size);
	    break;
        default:
            break;
        }
    }

    if (!dynamic)
        goto the_end;

    /* compute the real library name */
    soname = tcc_basename(filename);
    for(i = 0, dt = dynamic; i < nb_dts; i++, dt++)
        if (dt->d_tag == DT_SONAME)
            soname = dynstr + dt->d_un.d_val;

    /* if the dll is already loaded, do not load it */
    if (tcc_add_dllref(s1, soname, level)->found)
        goto ret_success;

    if (v.nb_versyms != nb_syms)
        tcc_free (v.versym), v.versym = NULL;
    else
        store_version(s1, &v, dynstr);

    /* add dynamic symbols in dynsym_section */
    for(i = 1, sym = dynsym + 1; i < nb_syms; i++, sym++) {
        sym_bind = ELFW(ST_BIND)(sym->st_info);
        if (sym_bind == STB_LOCAL)
            continue;
        name = dynstr + sym->st_name;
        sym_index = set_elf_sym(s1->dynsymtab_section, sym->st_value, sym->st_size,
                                sym->st_info, sym->st_other, sym->st_shndx, name);
        if (v.versym) {
            ElfW(Half) vsym = v.versym[i];
            if ((vsym & 0x8000) == 0 && vsym > 0 && vsym < v.nb_local_ver)
                set_sym_version(s1, sym_index, v.local_ver[vsym]);
        }
    }

    for(i = 0, dt = dynamic; i < nb_dts; i++, dt++)
        if (dt->d_tag == DT_RPATH)
            tcc_add_library_path(s1, dynstr + dt->d_un.d_val);

    /* load all referenced DLLs */
    for(i = 0, dt = dynamic; i < nb_dts; i++, dt++) {
        switch(dt->d_tag) {
        case DT_NEEDED:
            name = dynstr + dt->d_un.d_val;
            if (tcc_add_dllref(s1, name, -1))
                continue;
            if (tcc_add_dll(s1, name, AFF_REFERENCED_DLL) < 0) {
                tcc_error_noabort("referenced dll '%s' not found", name);
                goto the_end;
            }
        }
    }

 ret_success:
    ret = 0;
 the_end:
    tcc_free(dynstr);
    tcc_free(dynsym);
    tcc_free(dynamic);
    tcc_free(shdr);
    tcc_free(v.local_ver);
    tcc_free(v.verdef);
    tcc_free(v.verneed);
    tcc_free(v.versym);
    return ret;
}

#define LD_TOK_NAME 256
#define LD_TOK_EOF  (-1)

static int ld_inp(TCCState *s1)
{
    char b;
    if (s1->cc != -1) {
        int c = s1->cc;
        s1->cc = -1;
        return c;
    }
    if (1 == read(s1->fd, &b, 1))
        return b;
    return CH_EOF;
}

/* return next ld script token */
static int ld_next(TCCState *s1, char *name, int name_size)
{
    int c, d, ch;
    char *q;

 redo:
    ch = ld_inp(s1);
    switch(ch) {
    case ' ':
    case '\t':
    case '\f':
    case '\v':
    case '\r':
    case '\n':
        goto redo;
    case '/':
        ch = ld_inp(s1);
        if (ch == '*') { /* comment */
            for (d = 0;; d = ch) {
                ch = ld_inp(s1);
                if (ch == CH_EOF || (ch == '/' && d == '*'))
                    break;
            }
            goto redo;
        } else {
            q = name;
            *q++ = '/';
            goto parse_name;
        }
        break;
    case '\\':
    /* case 'a' ... 'z': */
    case 'a':
       case 'b':
       case 'c':
       case 'd':
       case 'e':
       case 'f':
       case 'g':
       case 'h':
       case 'i':
       case 'j':
       case 'k':
       case 'l':
       case 'm':
       case 'n':
       case 'o':
       case 'p':
       case 'q':
       case 'r':
       case 's':
       case 't':
       case 'u':
       case 'v':
       case 'w':
       case 'x':
       case 'y':
       case 'z':
    /* case 'A' ... 'z': */
    case 'A':
       case 'B':
       case 'C':
       case 'D':
       case 'E':
       case 'F':
       case 'G':
       case 'H':
       case 'I':
       case 'J':
       case 'K':
       case 'L':
       case 'M':
       case 'N':
       case 'O':
       case 'P':
       case 'Q':
       case 'R':
       case 'S':
       case 'T':
       case 'U':
       case 'V':
       case 'W':
       case 'X':
       case 'Y':
       case 'Z':
    case '_':
    case '.':
    case '$':
    case '~':
        q = name;
    parse_name:
        for(;;) {
            if (!((ch >= 'a' && ch <= 'z') ||
                  (ch >= 'A' && ch <= 'Z') ||
                  (ch >= '0' && ch <= '9') ||
                  strchr("/.-_+=$:\\,~", ch)))
                break;
            if ((q - name) < name_size - 1) {
                *q++ = ch;
            }
            ch = ld_inp(s1);
        }
        s1->cc = ch;
        *q = '\0';
        c = LD_TOK_NAME;
        break;
    case CH_EOF:
        c = LD_TOK_EOF;
        break;
    default:
        c = ch;
        break;
    }
    return c;
}

static int ld_add_file(TCCState *s1, const char filename[])
{
    if (filename[0] == '/') {
        if (CONFIG_SYSROOT[0] == '\0'
            && tcc_add_file_internal(s1, filename, AFF_TYPE_BIN) == 0)
            return 0;
        filename = tcc_basename(filename);
    }
    return tcc_add_dll(s1, filename, 0);
}

static int ld_add_file_list(TCCState *s1, const char *cmd, int as_needed)
{
    char filename[1024], libname[1024];
    int t, group, nblibs = 0, ret = 0;
    char **libs = NULL;

    group = !strcmp(cmd, "GROUP");
    if (!as_needed)
        s1->new_undef_sym = 0;
    t = ld_next(s1, filename, sizeof(filename));
    if (t != '(') {
        tcc_error_noabort("( expected");
        ret = -1;
        goto lib_parse_error;
    }
    t = ld_next(s1, filename, sizeof(filename));
    for(;;) {
        libname[0] = '\0';
        if (t == LD_TOK_EOF) {
            tcc_error_noabort("unexpected end of file");
            ret = -1;
            goto lib_parse_error;
        } else if (t == ')') {
            break;
        } else if (t == '-') {
            t = ld_next(s1, filename, sizeof(filename));
            if ((t != LD_TOK_NAME) || (filename[0] != 'l')) {
                tcc_error_noabort("library name expected");
                ret = -1;
                goto lib_parse_error;
            }
            pstrcpy(libname, sizeof libname, &filename[1]);
            if (s1->static_link) {
                snprintf(filename, sizeof filename, "lib%s.a", libname);
            } else {
                snprintf(filename, sizeof filename, "lib%s.so", libname);
            }
        } else if (t != LD_TOK_NAME) {
            tcc_error_noabort("filename expected");
            ret = -1;
            goto lib_parse_error;
        }
        if (!strcmp(filename, "AS_NEEDED")) {
            ret = ld_add_file_list(s1, cmd, 1);
            if (ret)
                goto lib_parse_error;
        } else {
            /* TODO: Implement AS_NEEDED support. Ignore it for now */
            if (!as_needed) {
                ret = ld_add_file(s1, filename);
                if (ret)
                    goto lib_parse_error;
                if (group) {
                    /* Add the filename *and* the libname to avoid future conversions */
                    dynarray_add(&libs, &nblibs, tcc_strdup(filename));
                    if (libname[0] != '\0')
                        dynarray_add(&libs, &nblibs, tcc_strdup(libname));
                }
            }
        }
        t = ld_next(s1, filename, sizeof(filename));
        if (t == ',') {
            t = ld_next(s1, filename, sizeof(filename));
        }
    }
    if (group && !as_needed) {
        while (s1->new_undef_sym) {
            int i;
            s1->new_undef_sym = 0;
            for (i = 0; i < nblibs; i ++)
                ld_add_file(s1, libs[i]);
        }
    }
lib_parse_error:
    dynarray_reset(&libs, &nblibs);
    return ret;
}

/* interpret a subset of GNU ldscripts to handle the dummy libc.so
   files */
ST_FUNC int tcc_load_ldscript(TCCState *s1, int fd)
{
    char cmd[64];
    char filename[1024];
    int t, ret;

    s1->fd = fd;
    s1->cc = -1;
    for(;;) {
        t = ld_next(s1, cmd, sizeof(cmd));
        if (t == LD_TOK_EOF)
            return 0;
        else if (t != LD_TOK_NAME)
            return -1;
        if (!strcmp(cmd, "INPUT") ||
            !strcmp(cmd, "GROUP")) {
            ret = ld_add_file_list(s1, cmd, 0);
            if (ret)
                return ret;
        } else if (!strcmp(cmd, "OUTPUT_FORMAT") ||
                   !strcmp(cmd, "TARGET")) {
            /* ignore some commands */
            t = ld_next(s1, cmd, sizeof(cmd));
            if (t != '(') {
                tcc_error_noabort("( expected");
                return -1;
            }
            for(;;) {
                t = ld_next(s1, filename, sizeof(filename));
                if (t == LD_TOK_EOF) {
                    tcc_error_noabort("unexpected end of file");
                    return -1;
                } else if (t == ')') {
                    break;
                }
            }
        } else {
            return -1;
        }
    }
    return 0;
}
#endif /* !ELF_OBJ_ONLY */