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[an error occurred while processing this directive]
int main(){
int A[3];
printf("a");
A[3] = 1;
return 0;
}
‚±‚ê‚ðŽÀs‚·‚é‚ÆAŒ‹‰Ê‚Í’P‚ÉSegmentation Fault‚Æo‚邾‚¯‚ÅA‚Ç‚±‚ª‚¨‚©‚µ‚¢‚©‚í‚©‚ç‚È‚¢B
‚±‚ê‚ð
printf("a\n");
–”‚Í
printf("a");
fflush(stdout);
‚Æ‚·‚é‚ÆA‚¿‚á‚ñ‚Æa‚ð•\Ž¦‚µ‚½Œã‚Å—Ž‚¿‚Ä‚‚ê‚éB
#define OUT(A) printf("%s = %d\n",#A, A)
‚Æ‚¢‚¤ƒ}ƒNƒ‚ð’è‹`‚µ‚Ä‚¨‚‚ÆA
int main(){
int i = 3;
OUT(i);
}
‚Æ‚·‚邾‚¯‚ÅA
i = 3‚Ý‚½‚¢‚Èo—Í‚ª“¾‚ç‚ê‚éB‚±‚ê‚Í%d‚©‚番‚©‚é‚悤‚É®”‚É‚µ‚©Žg‚¦‚È‚¢‚¯‚ÇAC++Žg‚Á‚Ä‚é‚È‚ç
#include<iostream>
#define OUT(A) std::cout << #A << '='<<A << std::endl;
int main(){
int i = 3;
OUT(i);
}
‚Æ‚·‚é‚ÆAint‚Å‚àdouble‚Å‚àstring‚Å‚àŽg‚¦‚Ü‚·B
#include <assert.h> ‚±‚ê‚Í擪‚É‘‚
...
assert(x != 0);
‚±‚¤‚·‚é‚ÆA‚à‚µx‚ª0‚É‚È‚Á‚½‚Æ‚«‚É‚¿‚傤‚Ç‚»‚±‚Å—Ž‚¿‚Ä‚‚ê‚Ü‚·B
ŽŸ‚Ìgdb‚Æ‘g‚݇‚킹‚é‚ÆAƒfƒoƒbƒO‚Ì‹‚¢–¡•û‚É‚È‚è‚Ü‚·B
$ gcc test.c -g -o test‚ÅAgdb‚ÉH‚킹‚éB
$ gdb test (gdb)‚±‚±‚ÅA?‚Ƒł‚Ǝg‚¦‚éƒRƒ}ƒ“ƒh‚̈ꗗ‚ªo‚éB
#include <stdio.h>
void init(int *A, int size){
int i;
for(i = 0; i < size; i++)
A[i] = i * i;
}
void print(int *A, int size){
int i;
for(i = 0; i < size; i++)
printf("A[%d] = %d\n", i, A[i]);
}
int main(void){
int i;
int size = 4;
int A[4];
init(A, size);
A[1000] = 10;
print(A, size);
}
ŽÀs‚µ‚½‚çA‘½•ªA[1000] = 10;‚Ìs‚Å—Ž‚¿‚Ü‚·B
‚»‚±‚Å‚±‚ê‚ðgdb‚ÅŽÀsB
$ gdb test (gdb) run (‚Æ‚è‚ ‚¦‚¸ŽÀs) Program received signal SIGSEGV, Segmentation fault. main () at test.c:22 (gdb) where (¡‚Ç‚±‚É‚¢‚é‚©‚ð•\Ž¦) #0 main () at test.c:22 (gdb) list (¡‚¢‚é‚ ‚½‚è‚̃\[ƒX‚ð•\Ž¦) 21 init(A, size); 22 A[1000] = 10; 23 print(A, size); (gdb) print A[0] (A[0]‚Ì’†g‚ð•\Ž¦) $1 = 0 (gdb) call print(A, size) (print‚Á‚ÄŠÖ”‚ðŒÄ‚ñ‚Å‚Ý‚é) A[0] = 0 A[1] = 1 A[2] = 4 A[3] = 9 (gdb)‚±‚ñ‚ÈŠ´‚¶‚ÅAA•Ï”’†g‚ðŠÈ’P‚É‚Ì‚¼‚¯‚éB
(gdb) break init
‚Æ‚·‚é‚ÆAinit()‚É“ü‚Á‚½‚Æ‚±‚ÅŽ~‚Ü‚é‚©‚çA‚»‚±‚©‚çstep‚ňês‚¸‚Âi‚ß‚½‚è‚Å‚«‚éB
#include<stdio.h>
typedef struct kei_{
int i;
} kei;
kei *new(){
kei *k;
k = (kei *)malloc(sizeof(kei));
k->i = 23;
/* ‚±‚±‚Éreturn k‚ª‚È‚¢ */
}
int main(){
kei *k;
k = new();
printf("%d\n", k->i);
}
‚±‚ê‚ðŽÀs‚·‚é‚ÆA–l‚̊‹«‚Å‚Í23‚Æ•\Ž¦‚³‚ê‚Ü‚µ‚½‚ªAƒRƒ“ƒpƒCƒ‹ƒIƒvƒVƒ‡ƒ“‚ð-O3‚É•Ï‚¦‚é‚Æ“®‚©‚È‚‚È‚è‚Ü‚µ‚½B
‚±‚¤‚¢‚¤‚½‚¿‚̈«‚¢ƒoƒO‚ð–h‚®‚É‚ÍA
% gcc -g -Wall test.c‚Æ‚µ‚ăRƒ“ƒpƒCƒ‹‚·‚é‚ÆA
warning: control reaches end of non-void function‚ÆŒx‚ðo‚µ‚Ä‚‚ê‚Ü‚·B
gcc test.c -lefence‚Æ‚·‚邾‚¯‚Å‚·Bo—ˆ‚½ƒoƒCƒiƒŠ‚Í•’Ê‚ÉŽÀs‚µ‚ĉº‚³‚¢B ŽÀsŽž‚É"Electric Fence‚È‚ñ‚Æ‚©"‚Á‚ăƒbƒZ[ƒW‚ªo‚ê‚΂¿‚á‚ñ‚ƃŠƒ“ƒN‚³‚ê‚Ä‚Ü‚·B
#ifdef DEBUG #define DPRINT(s...) fprintf(stderr, s) #else #define DPRINT(s...) #endifƒR[ƒh‚Ì‚Ù‚¤‚Í‚±‚ñ‚È‚Ó‚¤‚É‘‚B
DPRINT("debug message %d\n", i);
‚»‚Ì‚¤‚¦‚ÅAdebug ‚µ‚½‚¢‚Æ‚«‚Í #define DEBUG ‚·‚é‚ÆAƒƒbƒZ[ƒW‚ª•\Ž¦‚³‚ê‚éB
ˆÀ’肵‚Ä‚«‚½‚çAdefine DEBUG ‚ð‚Í‚¸‚¹‚΂悢B
void err_printf(const char *format, ...){
va_list arg;
char buf[MAX_LEN];
va_start(arg, format);
vsprintf(buf, format, arg);
va_end(arg);
fprintf(FP, buf);
}