Question

当我运行我的代码时，valgrind会发出此错误。

   Invalid free() / delete / delete[] / realloc()
   ==7363==    at 0x4C2A82E: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
   ==7363==    by 0x4009F8: main (in /home/arihant/ELF/elf)
   ==7363==  Address 0x51f3fa0 is 0 bytes inside a block of size 16 free'd
   ==7363==    at 0x4C2A82E: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
   ==7363==    by 0x4009B1: main (in /home/arihant/ELF/elf)
   ==7363== 
   ==7363== 
   ==7363== HEAP SUMMARY:
   ==7363==     in use at exit: 160 bytes in 4 blocks
   ==7363==   total heap usage: 448 allocs, 448 frees, 34,684 bytes allocated
   ==7363== 
   ==7363== LEAK SUMMARY:
   ==7363==    definitely lost: 160 bytes in 4 blocks
   ==7363==    indirectly lost: 0 bytes in 0 blocks
   ==7363==      possibly lost: 0 bytes in 0 blocks
   ==7363==    still reachable: 0 bytes in 0 blocks
   ==7363==         suppressed: 0 bytes in 0 blocks
   ==7363== Rerun with --leak-check=full to see details of leaked memory
   ==7363== 
   ==7363== For counts of detected and suppressed errors, rerun with: -v
   ==7363== ERROR SUMMARY: 6 errors from 2 contexts (suppressed: 2 from 2)

为什么我会丢失160个字节，尽管alloc的数量和free相等

我的代码是

     18         fp = fopen("output", "r");
     19         obj_elf = (Elf32_Ehdr *)malloc(sizeof(Elf32_Ehdr));
     20         fread(obj_elf, 1, sizeof(Elf32_Ehdr), fp);
     21 
     22         if (argc < 2) {
     23                 print_menu();
     24                 free(obj_elf);
     25                 fclose(fp);
     26                 return 0;
     27         }
     28 
     29         if (argv[1][0] == '-') {
     30                 switch (argv[1][1]) {
     31                 case 'e':
     32                         elf_header(obj_elf); /*elf header function call*/
     33                         break;
     34                 case 's':
     35                         read_section_header(fp, obj_elf, obj_sect_hdr);
     36                         print_section_header(fp, obj_sect_hdr, obj_elf);
     37 
     38                         for (i = 0; i < obj_elf->e_shnum; i++) {
     39                                 free(obj_sect_hdr[i]);
     40                                 free(sec_name[i]);
     41                         }
     42                         break;
     43                 case 'S':
     44                         read_section_header(fp, obj_elf, obj_sect_hdr);
     45                         read_symbol_table(fp, obj_elf, obj_sect_hdr, obj_sym);
     46                         symbol_table(fp, obj_elf, obj_sect_hdr, obj_sym);
     47 
     48                         for (i = 0; i < obj_elf->e_shnum; i++) {
     49                                 free(obj_sect_hdr[i]);
     50                                 free(sec_name[i]);
     51                         }
     52                         for (i = 0; i < n_entries_sym_t; i++) {
     53                                 free(obj_sym[i]);
     54                                 free(symbol_name[i]);
     55                         }
     56

在main函数中有很多free我怎么知道哪个free是无效的？

Answer 1

您的答案位于输出的顶部：

   Invalid free() / delete / delete[] / realloc()
   ==7363==    at 0x4C2A82E: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
   ==7363==    by 0x4009F8: main (in /home/arihant/ELF/elf)
   ==7363==  Address 0x51f3fa0 is 0 bytes inside a block of size 16 free'd
   ==7363==    at 0x4C2A82E: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
   ==7363==    by 0x4009B1: main (in /home/arihant/ELF/elf)

当您的一个或多个免费通话无效时，仅仅匹配分配和释放的数量是不够的。您需要使用调试来构建以查看哪个free（）是问题。看起来它可能是在read_section_header（）中分配的东西或未列出的其他东西。

valgrind在4个块中给出160个字节，尽管总堆使用率是：448个allocs，448个frees，34,684个字节分配

1 个答案: