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#include <cpptrace/cpptrace.hpp>
#include <cpptrace/from_current.hpp>
#include <cstdint>
#include <exception>
#include <system_error>
#include <typeinfo>
#include "platform/platform.hpp"
#include "platform/memory_mapping.hpp"
#include "utils/error.hpp"
#include "utils/microfmt.hpp"
#include "utils/utils.hpp"
#include "logging.hpp"
#include "unwind/unwind.hpp"
#ifndef _MSC_VER
#include <cstring>
#endif
CPPTRACE_BEGIN_NAMESPACE
namespace detail {
thread_local lazy_trace_holder current_exception_trace;
thread_local lazy_trace_holder saved_rethrow_trace;
bool& get_rethrow_switch() {
static thread_local bool rethrow_switch = false;
return rethrow_switch;
}
void save_current_trace(raw_trace trace) {
if(get_rethrow_switch()) {
saved_rethrow_trace = lazy_trace_holder(std::move(trace));
} else {
current_exception_trace = lazy_trace_holder(std::move(trace));
saved_rethrow_trace = lazy_trace_holder();
}
}
#if defined(_MSC_VER) && defined(CPPTRACE_UNWIND_WITH_DBGHELP)
CPPTRACE_FORCE_NO_INLINE void collect_current_trace(std::size_t skip, EXCEPTION_POINTERS* exception_ptrs) {
try {
#if defined(_M_IX86) || defined(__i386__)
(void)skip; // don't skip any frames, the context record is at the throw point
auto trace = raw_trace{detail::capture_frames(0, SIZE_MAX, exception_ptrs)};
#else
(void)exception_ptrs;
auto trace = raw_trace{detail::capture_frames(skip + 1, SIZE_MAX)};
#endif
save_current_trace(std::move(trace));
} catch(...) {
detail::log_and_maybe_propagate_exception(std::current_exception());
}
}
#else
CPPTRACE_FORCE_NO_INLINE void collect_current_trace(std::size_t skip) {
try {
auto trace = raw_trace{detail::capture_frames(skip + 1, SIZE_MAX)};
save_current_trace(std::move(trace));
} catch(...) {
detail::log_and_maybe_propagate_exception(std::current_exception());
}
}
#endif
#ifdef _MSC_VER
// https://www.youtube.com/watch?v=COEv2kq_Ht8
// https://github.com/tpn/pdfs/blob/master/2018%20CppCon%20Unwinding%20the%20Stack%20-%20Exploring%20how%20C%2B%2B%20Exceptions%20work%20on%20Windows%20-%20James%20McNellis.pdf
// https://github.com/ecatmur/stacktrace-from-exception/blob/main/stacktrace-from-exception.cpp
// https://github.com/wine-mirror/wine/blob/7f833db11ffea4f3f4fa07be31d30559aff9c5fb/dlls/msvcrt/except.c#L371
// https://github.com/facebook/folly/blob/d17bf897cb5bbf8f07b122a614e8cffdc38edcde/folly/lang/Exception.cpp
// ClangCL doesn't define ThrowInfo so we use our own
// sources:
// - https://github.com/ecatmur/stacktrace-from-exception/blob/main/stacktrace-from-exception.cpp
// - https://github.com/catboost/catboost/blob/master/contrib/libs/cxxsupp/libcxx/src/support/runtime/exception_pointer_msvc.ipp
// - https://www.geoffchappell.com/studies/msvc/language/predefined/index.htm
#pragma pack(push, 4)
struct CatchableType {
std::uint32_t properties;
std::int32_t pType;
std::uint32_t non_virtual_adjustment; // these next three are from _PMD
std::uint32_t offset_to_virtual_base_ptr;
std::uint32_t virtual_base_table_index;
std::uint32_t sizeOrOffset;
std::int32_t copyFunction;
};
struct ThrowInfo {
std::uint32_t attributes;
std::int32_t pmfnUnwind;
std::int32_t pForwardCompat;
std::int32_t pCatchableTypeArray;
};
#pragma warning(push)
#pragma warning(disable:4200)
#if IS_CLANG
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wc99-extensions"
#endif
struct CatchableTypeArray {
uint32_t nCatchableTypes;
int32_t arrayOfCatchableTypes[];
};
#if IS_CLANG
#pragma clang diagnostic pop
#endif
#pragma warning(pop)
#pragma pack(pop)
static constexpr unsigned EH_MAGIC_NUMBER1 = 0x19930520; // '?msc' version magic, see ehdata.h
static constexpr unsigned EH_EXCEPTION_NUMBER = 0xE06D7363; // '?msc', 'msc' | 0xE0000000
using catchable_type_array_t = decltype(ThrowInfo::pCatchableTypeArray);
class catchable_type_info {
HMODULE module_pointer = nullptr;
const CatchableTypeArray* catchable_types = nullptr;
public:
catchable_type_info(const HMODULE module_pointer, catchable_type_array_t catchable_type_array)
: module_pointer(module_pointer) {
catchable_types = rtti_rva<const CatchableTypeArray*>(catchable_type_array);
}
class iterator {
const catchable_type_info& info;
std::size_t i;
public:
iterator(const catchable_type_info& info, std::size_t i) : info(info), i(i) {}
const std::type_info& operator*() const {
return info.get_type_info(i);
}
bool operator!=(const iterator& other) const {
return i != other.i;
}
iterator& operator++() {
i++;
return *this;
}
};
using const_iterator = iterator;
const_iterator begin() const {
return {*this, 0};
}
const_iterator end() const {
return {*this, catchable_types ? catchable_types->nCatchableTypes : std::size_t{}};
}
private:
template<typename T, typename A>
T rtti_rva(A address) const {
#ifdef _WIN64
return reinterpret_cast<T>((uintptr_t)module_pointer + (uintptr_t)address);
#else
(void)module_pointer;
return reinterpret_cast<T>(address);
#endif
}
const std::type_info& get_type_info(std::size_t i) const {
return *rtti_rva<const std::type_info*>(get_catchable_type(i)->pType);
}
const CatchableType* get_catchable_type(std::size_t i) const {
return rtti_rva<const CatchableType*>(
reinterpret_cast<const std::int32_t*>(catchable_types->arrayOfCatchableTypes)[i]
);
}
};
catchable_type_info get_catchable_types(const EXCEPTION_RECORD* exception_record) {
static_assert(EXCEPTION_MAXIMUM_PARAMETERS >= 4, "Unexpected EXCEPTION_MAXIMUM_PARAMETERS");
// ExceptionInformation will contain
// [0] EH_MAGIC_NUMBER1
// [1] ExceptionObject
// [2] ThrowInfo
HMODULE module_pointer = nullptr;
catchable_type_array_t catchable_type_array{}; // will be either an int or pointer
if(
exception_record->ExceptionInformation[0] == EH_MAGIC_NUMBER1
&& exception_record->NumberParameters >= 3
) {
if(exception_record->NumberParameters >= 4) {
module_pointer = reinterpret_cast<HMODULE>(exception_record->ExceptionInformation[3]);
}
auto throw_info = reinterpret_cast<const ThrowInfo*>(exception_record->ExceptionInformation[2]);
if (throw_info) {
catchable_type_array = throw_info->pCatchableTypeArray;
}
}
return {module_pointer, catchable_type_array};
}
bool matches_exception(EXCEPTION_RECORD* exception_record, const std::type_info& type_info) {
if (type_info == typeid(void)) {
return true;
}
for (const auto& catchable_type : get_catchable_types(exception_record)) {
if (catchable_type == type_info) {
return true;
}
}
return false;
}
#endif
#ifndef _MSC_VER
#if IS_LIBSTDCXX
constexpr size_t vtable_size = 11;
#elif IS_LIBCXX
constexpr size_t vtable_size = 10;
#else
#warning "Cpptrace from_current: Unrecognized C++ standard library, from_current() won't be supported"
constexpr size_t vtable_size = 0;
#endif
void perform_typeinfo_surgery(const std::type_info& info, bool(*do_catch_function)(const std::type_info*, const std::type_info*, void**, unsigned)) {
if(vtable_size == 0) { // set to zero if we don't know what standard library we're working with
return;
}
void* type_info_pointer = const_cast<void*>(static_cast<const void*>(&info));
void** type_info_vtable_pointer = *static_cast<void***>(type_info_pointer);
// the type info vtable pointer points to two pointers inside the vtable, adjust it back
// https://itanium-cxx-abi.github.io/cxx-abi/abi.html#vtable-components (see offset to top, typeinfo ptr,
// and the following bullet point)
type_info_vtable_pointer -= 2;
// for libstdc++ the class type info vtable looks like
// 0x7ffff7f89d18 <_ZTVN10__cxxabiv117__class_type_infoE>: 0x0000000000000000 0x00007ffff7f89d00
// [offset ][typeinfo pointer ]
// 0x7ffff7f89d28 <_ZTVN10__cxxabiv117__class_type_infoE+16>: 0x00007ffff7dd65a0 0x00007ffff7dd65c0
// [base destructor ][deleting dtor ]
// 0x7ffff7f89d38 <_ZTVN10__cxxabiv117__class_type_infoE+32>: 0x00007ffff7dd8f10 0x00007ffff7dd8f10
// [__is_pointer_p ][__is_function_p ]
// 0x7ffff7f89d48 <_ZTVN10__cxxabiv117__class_type_infoE+48>: 0x00007ffff7dd6640 0x00007ffff7dd6500
// [__do_catch ][__do_upcast ]
// 0x7ffff7f89d58 <_ZTVN10__cxxabiv117__class_type_infoE+64>: 0x00007ffff7dd65e0 0x00007ffff7dd66d0
// [__do_upcast ][__do_dyncast ]
// 0x7ffff7f89d68 <_ZTVN10__cxxabiv117__class_type_infoE+80>: 0x00007ffff7dd6580 0x00007ffff7f8abe8
// [__do_find_public_src][other ]
// In libc++ the layout is
// [offset ][typeinfo pointer ]
// [base destructor ][deleting dtor ]
// [noop1 ][noop2 ]
// [can_catch ][search_above_dst ]
// [search_below_dst ][has_unambiguous_public_base]
// Relevant documentation/implementation:
// https://itanium-cxx-abi.github.io/cxx-abi/abi.html
// libstdc++
// https://github.com/gcc-mirror/gcc/blob/b13e34699c7d27e561fcfe1b66ced1e50e69976f/libstdc%252B%252B-v3/libsupc%252B%252B/typeinfo
// https://github.com/gcc-mirror/gcc/blob/b13e34699c7d27e561fcfe1b66ced1e50e69976f/libstdc%252B%252B-v3/libsupc%252B%252B/class_type_info.cc
// libc++
// https://github.com/llvm/llvm-project/blob/648f4d0658ab00cf1e95330c8811aaea9481a274/libcxx/include/typeinfo
// https://github.com/llvm/llvm-project/blob/648f4d0658ab00cf1e95330c8811aaea9481a274/libcxxabi/src/private_typeinfo.h
// shouldn't be anything other than 4096 but out of an abundance of caution
auto page_size = get_page_size();
if(page_size <= 0 && is_positive_power_of_two(page_size)) {
throw internal_error("getpagesize() is not a power of 2 greater than zero (was {})", page_size);
}
if(static_cast<size_t>(page_size) < vtable_size * sizeof(void*)) {
throw internal_error(
"Page size isn't big enough for a vtable: Needed {}, got {}",
vtable_size * sizeof(void*),
page_size
);
}
// allocate a page for the new vtable so it can be made read-only later
// the OS cleans this up, no cleanup done here for it
void* new_vtable_page = allocate_page(page_size);
// Double-check alignment: "This address must have the alignment required for pointers"
// https://itanium-cxx-abi.github.io/cxx-abi/abi.html#vtable-components
constexpr auto ptr_align = alignof(void*);
static_assert(is_positive_power_of_two(ptr_align), "alignof has to return a power of two");
auto align_mask = ptr_align - 1;
if((reinterpret_cast<uintptr_t>(new_vtable_page) & align_mask) != 0) {
throw internal_error("Bad allocation alignment: {}", reinterpret_cast<uintptr_t>(new_vtable_page));
}
// make our own copy of the vtable
std::memcpy(new_vtable_page, type_info_vtable_pointer, vtable_size * sizeof(void*));
// ninja in the custom __do_catch interceptor
auto new_vtable = static_cast<void**>(new_vtable_page);
// double cast is done here because older (and some newer gcc versions) warned about it under -Wpedantic
new_vtable[6] = reinterpret_cast<void*>(reinterpret_cast<std::uintptr_t>(do_catch_function));
// make the page read-only
mprotect_page(new_vtable_page, page_size, memory_readonly);
// make the vtable pointer for unwind_interceptor's type_info point to the new vtable
auto type_info_addr = reinterpret_cast<uintptr_t>(type_info_pointer);
auto page_addr = type_info_addr & ~(page_size - 1);
// make sure the memory we're going to set is within the page
if(type_info_addr - page_addr + sizeof(void*) > static_cast<unsigned>(page_size)) {
throw internal_error("pointer crosses page boundaries");
}
auto old_protections = mprotect_page_and_return_old_protections(
reinterpret_cast<void*>(page_addr),
page_size,
memory_readwrite
);
*static_cast<void**>(type_info_pointer) = static_cast<void*>(new_vtable + 2);
mprotect_page(reinterpret_cast<void*>(page_addr), page_size, old_protections);
}
bool can_catch(
const std::type_info* type,
const std::type_info* throw_type,
void** throw_obj,
unsigned outer
) {
if (*type == typeid(void)) {
return true;
}
// get the vtable for the type_info and call the function pointer in the 6th slot
// see below: perform_typeinfo_surgery
void* type_info_pointer = const_cast<void*>(static_cast<const void*>(type));
void** type_info_vtable_pointer = *static_cast<void***>(type_info_pointer);
// the type info vtable pointer points to two pointers inside the vtable, adjust it back
type_info_vtable_pointer -= 2;
auto* can_catch_fn =
#if IS_GCC
// error: ISO C++ forbids casting between pointer-to-function and pointer-to-object on old gcc
__extension__
#endif
reinterpret_cast<decltype(can_catch)*>(type_info_vtable_pointer[6]);
return can_catch_fn(type, throw_type, throw_obj, outer);
}
#endif
// called when unwinding starts after rethrowing, after search phase
void rethrow_scope_cleanup() {
get_rethrow_switch() = false;
}
scope_guard<void(&)()> setup_rethrow() {
get_rethrow_switch() = true;
// will flip the switch back to true as soon as the search phase completes and the unwinding begins
return scope_exit<void(&)()>(rethrow_scope_cleanup);
}
}
CPPTRACE_END_NAMESPACE
CPPTRACE_BEGIN_NAMESPACE
namespace detail {
#ifdef _MSC_VER
bool matches_exception(EXCEPTION_POINTERS* exception_ptrs, const std::type_info& type_info) {
CPPTRACE_PUSH_EXTENSION_WARNINGS
__try {
auto* exception_record = exception_ptrs->ExceptionRecord;
// Check if the SEH exception is a C++ exception
if(exception_record->ExceptionCode == EH_EXCEPTION_NUMBER) {
return detail::matches_exception(exception_record, type_info);
}
} __except(EXCEPTION_EXECUTE_HANDLER) {
// pass
}
CPPTRACE_POP_EXTENSION_WARNINGS
return false;
}
CPPTRACE_FORCE_NO_INLINE
int maybe_collect_trace(EXCEPTION_POINTERS* exception_ptrs, int filter_result) {
if(filter_result == EXCEPTION_EXECUTE_HANDLER) {
#ifdef CPPTRACE_UNWIND_WITH_DBGHELP
collect_current_trace(1, exception_ptrs);
#else
collect_current_trace(1);
(void)exception_ptrs;
#endif
}
return filter_result;
}
CPPTRACE_FORCE_NO_INLINE
void maybe_collect_trace(EXCEPTION_POINTERS* exception_ptrs, const std::type_info& type_info) {
if(matches_exception(exception_ptrs, type_info)) {
#ifdef CPPTRACE_UNWIND_WITH_DBGHELP
collect_current_trace(2, exception_ptrs);
#else
collect_current_trace(2);
(void)exception_ptrs;
#endif
}
}
#else
CPPTRACE_FORCE_NO_INLINE
void maybe_collect_trace(
const std::type_info* type,
const std::type_info* throw_type,
void** throw_obj,
unsigned outer
) {
if(detail::can_catch(type, throw_type, throw_obj, outer)) {
collect_current_trace(2);
}
}
void do_prepare_unwind_interceptor(const std::type_info& type_info, bool(*can_catch)(const std::type_info*, const std::type_info*, void**, unsigned)) {
try {
detail::perform_typeinfo_surgery(
type_info,
can_catch
);
} catch(std::exception& e) {
detail::log::error("Exception occurred while preparing from_current support: {}", e.what());
} catch(...) {
detail::log::error("Unknown exception occurred while preparing from_current support");
}
}
#endif
}
const raw_trace& raw_trace_from_current_exception() {
return detail::current_exception_trace.get_raw_trace();
}
const stacktrace& from_current_exception() {
return detail::current_exception_trace.get_resolved_trace();
}
const raw_trace& raw_trace_from_current_exception_rethrow() {
return detail::saved_rethrow_trace.get_raw_trace();
}
const stacktrace& from_current_exception_rethrow() {
return detail::saved_rethrow_trace.get_resolved_trace();
}
bool current_exception_was_rethrown() {
if(detail::saved_rethrow_trace.is_resolved()) {
return !detail::saved_rethrow_trace.get_resolved_trace().empty();
} else {
return !detail::saved_rethrow_trace.get_raw_trace().empty();
}
}
// The non-argument overload is to serve as room for possible future optimization under Microsoft's STL
CPPTRACE_FORCE_NO_INLINE void rethrow() {
auto guard = detail::setup_rethrow();
std::rethrow_exception(std::current_exception());
}
CPPTRACE_FORCE_NO_INLINE void rethrow(std::exception_ptr exception) {
auto guard = detail::setup_rethrow();
std::rethrow_exception(exception);
}
void clear_current_exception_traces() {
detail::current_exception_trace = detail::lazy_trace_holder{raw_trace{}};
detail::saved_rethrow_trace = detail::lazy_trace_holder{raw_trace{}};
}
CPPTRACE_END_NAMESPACE