为什么使用两个版本的 gcc 编译器会得到不同的结果？
使用 gcc 版本 4.9.2，我的程序可以在没有核心转储的情况下编译和运行。但使用 gcc 5.3 版本时，它编译时没有任何警告，但在执行时会转储核心。是什么导致了这种差异？我尝试过使用
malloc有问题的版本是
代码片段如下：
#include <stdio.h>
#include <string.h>
#include <strings.h>
#include <stdlib.h>
char *somval[12][2] =
{
{"one", "ONE"},
{"two", "TWO"},
{"three", "THREE"},
{"four", "FOUR"},
{"five", "FIVE"},
{"six", "SIX"},
{"seven", "SEVEN"},
{"eight", "EIGHT"},
{"nine", "NINE"},
{"ten", "TEN"},
{NULL, NULL}
};
typedef struct _getval
{
char **val1;
char **val2;
}GETVAL;
int main()
{
int i;
GETVAL *getval;
getval = calloc(1, sizeof(GETVAL));
getval->val1 = calloc(12, sizeof(int));
getval->val2 = calloc(12, sizeof(int));
for(i = 0; somval[i][1] != NULL; i++)
{
getval->val1[i] = calloc(101, sizeof(int));
getval->val1[i] = somval[i][0];
getval->val2[i] = somval[i][1];
printf("%s = %s\n", getval->val1[i], getval->val2[i]);
}
for(i = 0; somval[i][1] != NULL; i++)
{
free(getval->val1[i]);
}
free(getval->val1);
free(getval->val2);
free(getval);
return 0;
}
Compile the program with gcc or cc and valgrind ./a.out gives the following on gcc version 4.92. The program runs fine without a core dump and executed without valgrind.
==4818== Memcheck, a memory error detector
==4818== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==4818== Using Valgrind-3.10.1 and LibVEX; rerun with -h for copyright info
==4818== Command: ./a.out
==4818==
one = ONE
two = TWO
three = THREE
four = FOUR
five = FIVE
six = SIX
seven = SEVEN
eight = EIGHT
nine = NINE
ten = TEN
==4818== Invalid free() / delete / delete[] / realloc()
==4818== at 0x40082CD: free (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==4818== by 0x80485A1: main (in /users/netha/NTFiles/progs/cprog/test/a.out)
==4818== Address 0x8048684 is not stack'd, malloc'd or (recently) free'd
==4818==
==4818==
==4818== HEAP SUMMARY:
==4818== in use at exit: 4,040 bytes in 10 blocks
==4818== total heap usage: 13 allocs, 13 frees, 4,144 bytes allocated
==4818==
==4818== LEAK SUMMARY:
==4818== definitely lost: 4,040 bytes in 10 blocks
==4818== indirectly lost: 0 bytes in 0 blocks
==4818== possibly lost: 0 bytes in 0 blocks
==4818== still reachable: 0 bytes in 0 blocks
==4818== suppressed: 0 bytes in 0 blocks
==4818== Rerun with --leak-check=full to see details of leaked memory
==4818==
==4818== For counts of detected and suppressed errors, rerun with: -v
==4818== ERROR SUMMARY: 10 errors from 1 contexts (suppressed: 0 from 0)
----------------------------------------------------
Compile the program with gcc or cc and valgrind ./a.out gives the following on gcc version 5.3. The program runs fine without a core dump and executed with valgrind. Otherwise, the program dumps core without valgrind.
==29481== Memcheck, a memory error detector
==29481== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==29481== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info
==29481== Command: ./a.out
==29481==
one = ONE
two = TWO
three = THREE
four = FOUR
five = FIVE
six = SIX
==29481== Invalid write of size 8
==29481== at 0x400645: main (in /XtraStorage/netha/jayami/progs/cprog/gtk_examples/a.out)
==29481== Address 0x51f60c0 is 0 bytes after a block of size 48 alloc'd
==29481== at 0x4C2AA98: calloc (vg_replace_malloc.c:711)
==29481== by 0x4005F0: main (in /XtraStorage/netha/jayami/progs/cprog/gtk_examples/a.out)
==29481==
==29481== Invalid write of size 8
==29481== at 0x40066E: main (in /XtraStorage/netha/jayami/progs/cprog/gtk_examples/a.out)
==29481== Address 0x51f60c0 is 0 bytes after a block of size 48 alloc'd
==29481== at 0x4C2AA98: calloc (vg_replace_malloc.c:711)
==29481== by 0x4005F0: main (in /XtraStorage/netha/jayami/progs/cprog/gtk_examples/a.out)
==29481==
==29481== Invalid write of size 8
==29481== at 0x400698: main (in /XtraStorage/netha/jayami/progs/cprog/gtk_examples/a.out)
==29481== Address 0x51f6130 is 0 bytes after a block of size 48 alloc'd
==29481== at 0x4C2AA98: calloc (vg_replace_malloc.c:711)
==29481== by 0x400609: main (in /XtraStorage/netha/jayami/progs/cprog/gtk_examples/a.out)
==29481==
==29481== Invalid read of size 8
==29481== at 0x4006B0: main (in /XtraStorage/netha/jayami/progs/cprog/gtk_examples/a.out)
==29481== Address 0x51f6130 is 0 bytes after a block of size 48 alloc'd
==29481== at 0x4C2AA98: calloc (vg_replace_malloc.c:711)
==29481== by 0x400609: main (in /XtraStorage/netha/jayami/progs/cprog/gtk_examples/a.out)
==29481==
==29481== Invalid read of size 8
==29481== at 0x4006C7: main (in /XtraStorage/netha/jayami/progs/cprog/gtk_examples/a.out)
==29481== Address 0x51f60c0 is 0 bytes after a block of size 48 alloc'd
==29481== at 0x4C2AA98: calloc (vg_replace_malloc.c:711)
==29481== by 0x4005F0: main (in /XtraStorage/netha/jayami/progs/cprog/gtk_examples/a.out)
==29481==
seven = SEVEN
eight = EIGHT
nine = NINE
ten = TEN
==29481== Invalid free() / delete / delete[] / realloc()
==29481== at 0x4C29E00: free (vg_replace_malloc.c:530)
==29481== by 0x400722: main (in /XtraStorage/netha/jayami/progs/cprog/gtk_examples/a.out)
==29481== Address 0x400810 is in a r-x mapped file /XtraStorage/netha/jayami/progs/cprog/gtk_examples/a.out segment
==29481==
==29481== Invalid read of size 8
==29481== at 0x400718: main (in /XtraStorage/netha/jayami/progs/cprog/gtk_examples/a.out)
==29481== Address 0x51f60c0 is 0 bytes after a block of size 48 alloc'd
==29481== at 0x4C2AA98: calloc (vg_replace_malloc.c:711)
==29481== by 0x4005F0: main (in /XtraStorage/netha/jayami/progs/cprog/gtk_examples/a.out)
==29481==
==29481==
==29481== HEAP SUMMARY:
==29481== in use at exit: 4,040 bytes in 10 blocks
==29481== total heap usage: 13 allocs, 13 frees, 4,152 bytes allocated
==29481==
==29481== LEAK SUMMARY:
==29481== definitely lost: 4,040 bytes in 10 blocks
==29481== indirectly lost: 0 bytes in 0 blocks
==29481== possibly lost: 0 bytes in 0 blocks
==29481== still reachable: 0 bytes in 0 blocks
==29481== suppressed: 0 bytes in 0 blocks
==29481== Rerun with --leak-check=full to see details of leaked memory
==29481==
==29481== For counts of detected and suppressed errors, rerun with: -v
==29481== ERROR SUMMARY: 34 errors from 7 contexts (suppressed: 0 from 0)
val1val2sizeof(int)*val1*val2感谢您指出。我一直通过 sizeof(int) 分配内存，并且在这个新的 gcc 版本之前没有任何程序崩溃。我已经更新了代码并将其与 gcc 版本 5.3 上的 valgrind 结果粘贴在下面。我用 sizeof(void *) 替换了 sizeof(int)
#include <stdio.h>
#include <string.h>
#include <strings.h>
#include <stdlib.h>
char *somval[12][2] =
{
{"one", "ONE"},
{"two", "TWO"},
{"three", "THREE"},
{"four", "FOUR"},
{"five", "FIVE"},
{"six", "SIX"},
{"seven", "SEVEN"},
{"eight", "EIGHT"},
{"nine", "NINE"},
{"ten", "TEN"},
{NULL, NULL}
};
typedef struct _getval
{
char **val1;
char **val2;
}GETVAL;
int main()
{
int i;
GETVAL *getval;
getval = calloc(1, sizeof(GETVAL));
getval->val1 = calloc(12, sizeof(void *));
getval->val2 = calloc(12, sizeof(void *));
for(i = 0; somval[i][1] != NULL; i++)
{
getval->val1[i] = somval[i][0];
getval->val2[i] = somval[i][1];
printf("%s = %s\n", getval->val1[i], getval->val2[i]);
}
free(getval->val1);
free(getval->val2);
free(getval);
return 0;
}
-------------------------------------------
Compile with cc or gcc and ran with valgrind gave the below result. Without valgrind the program did not dump core.
==31006== Memcheck, a memory error detector
==31006== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==31006== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info
==31006== Command: ./a.out
==31006==
one = ONE
two = TWO
three = THREE
four = FOUR
five = FIVE
six = SIX
seven = SEVEN
eight = EIGHT
nine = NINE
ten = TEN
==31006==
==31006== HEAP SUMMARY:
==31006== in use at exit: 0 bytes in 0 blocks
==31006== total heap usage: 3 allocs, 3 frees, 208 bytes allocated
==31006==
==31006== All heap blocks were freed -- no leaks are possible
==31006==
==31006== For counts of detected and suppressed errors, rerun with: -v
==31006== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)