Question

我试图弄清楚我的valgrind调试有什么问题。我慢慢地学习这个valgrind。

调试：

==1701== HEAP SUMMARY:
==1701==     in use at exit: 390 bytes in 12 blocks
==1701==   total heap usage: 59 allocs, 47 frees, 1,097 bytes allocated
==1701==
==1701== 39 bytes in 1 blocks are definitely lost in loss record 6 of 12
==1701==    at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==1701==    by 0x401246: songToString (song.c:147)
==1701==    by 0x40083C: main (songtest.c:52)
==1701==

代码（songToString函数）：

char *songToString(const song *s)
{
    char *sstr = NULL ;
    char *st = NULL ;
    char *sa = NULL ;
    char *tt = NULL ;
    int len = 0 ;

    st = songGetTitle(s) ;
    sa = songGetArtist(s) ;

    // calculate the total string length needed.
    len = strlen("Title: ") + strlen(st) +
                  strlen("  Artist: ") + strlen(sa) + 1 ;

    if (NULL != s->lastPlayed)
    {
        tt = mtimeToString(s->lastPlayed) ;
        len += strlen(" at ") + strlen(tt) ;
    }

    // allocate enough space for the song
    sstr = malloc( len ) ;

    sprintf(sstr, "Title: %s  Artist: %s", st, sa) ;

    if (NULL != s->lastPlayed)
    {
        sstr = strcat(sstr, " at ") ;
        sstr = strcat(sstr, tt) ;
    }

    free(sa) ;
    free(st) ;
    free(tt) ;
    return sstr ;
}

在songToString中，第147行是sstr = malloc( len ) ;

歌曲测试中的

（第52行）：

char * sstr = songToString( song1 ) ;

任何帮助都会很棒。谢谢。

Answer 1

valgrind显示泄露的内存已分配，但实际的错误必须跟踪内存结束的位置。

显然，在sstr分配给main之后，您永远不会free。

Answer 2

@ o11c 你提出了错误的建议。见链接： http://c-faq.com/ptrs/passptrinit.html

另一个解决方案是让函数返回指针：

int *f()
{
    static int dummy = 5;
    return &dummy;
}

...

int *ip = f();

Valgrind的盖帽肯定会在损失记录中丢失

2 个答案: