c - Valgrind 内存泄漏可达

Question

printf 和 scanf 语句不断发生可访问内存泄漏。我需要完全没有泄漏。当我运行报告时，它说我在打印语句和扫描语句中得到了可到达的泄漏。我的问题是如何修复泄漏？

这是 valgrind 报告:

kidslove-MacBook:src kidslove$ valgrind --leak-check=full --show-leak-kinds=all ./a.out

==6405== Memcheck, a memory error detector
==6405== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==6405== Using Valgrind-3.11.0.SVN and LibVEX; rerun with -h for copyright info
==6405== Command: ./a.out
==6405== 
Enter File Name: input2.txt
1.  Print the array sorted by street.
2.  Print the array sorted by city.
3.  Print the array sorted by state then city
4.  Print the array sorrted by zip.
5.  Quit

--> 5
==6405== 
==6405== HEAP SUMMARY:
==6405==     in use at exit: 42,554 bytes in 422 blocks
==6405==   total heap usage: 513 allocs, 91 frees, 53,707 bytes allocated
==6405== 
==6405== 4,096 bytes in 1 blocks are still reachable in loss record 77 of 78
==6405==    at 0x1000076C1: malloc (vg_replace_malloc.c:303)
==6405==    by 0x1001F1836: __smakebuf (in /usr/lib/system/libsystem_c.dylib)
==6405==    by 0x100206387: __swsetup (in /usr/lib/system/libsystem_c.dylib)
==6405==    by 0x10022075D: __v2printf (in /usr/lib/system/libsystem_c.dylib)
==6405==    by 0x100220C80: __xvprintf (in /usr/lib/system/libsystem_c.dylib)
==6405==    by 0x1001F6B71: vfprintf_l (in /usr/lib/system/libsystem_c.dylib)
==6405==    by 0x1001F49D7: printf (in /usr/lib/system/libsystem_c.dylib)
==6405==    by 0x1000010B3: openFile (hw5.c:15)
==6405==    by 0x100001CD5: main (cscd240hw5.c:9)
==6405== 
==6405== 4,096 bytes in 1 blocks are still reachable in loss record 78 of 78
==6405==    at 0x1000076C1: malloc (vg_replace_malloc.c:303)
==6405==    by 0x1001F1836: __smakebuf (in /usr/lib/system/libsystem_c.dylib)
==6405==    by 0x1001F4E99: __srefill0 (in /usr/lib/system/libsystem_c.dylib)
==6405==    by 0x1001F4F94: __srefill (in /usr/lib/system/libsystem_c.dylib)
==6405==    by 0x1001FC00D: __svfscanf_l (in /usr/lib/system/libsystem_c.dylib)
==6405==    by 0x1001F515D: scanf (in /usr/lib/system/libsystem_c.dylib)
==6405==    by 0x1000010C8: openFile (hw5.c:16)
==6405==    by 0x100001CD5: main (cscd240hw5.c:9)
==6405== 
==6405== LEAK SUMMARY:
==6405==    definitely lost: 0 bytes in 0 blocks
==6405==    indirectly lost: 0 bytes in 0 blocks
==6405==      possibly lost: 0 bytes in 0 blocks
==6405==    still reachable: 8,192 bytes in 2 blocks
==6405==         suppressed: 34,362 bytes in 420 blocks
==6405== 
==6405== For counts of detected and suppressed errors, rerun with: -v
==6405== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 15 from 15)

返回泄漏的我程序的一部分:

FILE *openFile() {
  char name[20];
  FILE *fin;

  do {
    printf("Enter File Name: "); //line 15 leak
    scanf("%s", name); // line 16 leak
    fin = fopen(name, "r");
  }while(fin == NULL);
  return fin;

}

原来的电话是:

fin = openFile();

Answer 1

您系统上的标准 C 库似乎不会费心释放 stdio 使用的缓冲区。这没什么好担心的。当您的程序退出时，系统会释放内存。

通常操作系统提供的 valgrind 包包含抑制文件，这些文件告诉 valgrind 不要报告大量那些预期的泄漏。要么您使用的是非标准的 valgrind 包，要么您禁用了标准抑制，要么在该系统上构建 valgrind 的人没有打扰。