c - valgrind 中的内存

Question

我对 memory inn valgrind 有疑问。我一直在试图找出问题所在，但似乎找不到。这是我的问题:

==32233== Invalid write of size 1
==32233==    at 0x4C2E1E0: strcpy (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==32233==    by 0x4010C7: songCopy (song.c:102)
==32233==    by 0x4009E6: main (songtest.c:82)
==32233==  Address 0x51fda09 is 0 bytes after a block of size 9 alloc'd
==32233==    at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==32233==    by 0x4010A4: songCopy (song.c:101)
==32233==    by 0x4009E6: main (songtest.c:82)

这就是问题所在。

song *songCopy(const song *s)
{
//song *d = NULL ;
mtime *tmp = NULL ;

song *d = malloc(sizeof(song));

d->artist = malloc(sizeof(s->artist) + 1) ;
strcpy(d->artist, s->artist) ;

d->title = malloc(sizeof(s->title) + 1) ;
strcpy(d->title, s->title) ;

if (NULL != s->lastPlayed)
{
    // copy the last played
    tmp = mtimeCopy(s->lastPlayed) ;
    d->lastPlayed = tmp ;
}
else
{
    // set lastPlayed to NULL
    d->lastPlayed = NULL ;
}
return d ;

我已经尝试取消引用并向 malloc 添加更多空间。我知道它在 strcpy 中出错了，但我不确定为什么。

Answer 1

您没有显示song 的声明，但从用法上看它的artist 和title 成员是char * 指针。您可以使用 sizeof 来测量数组，但不能测量指针指向的 block 。 sizeof 对于您机器上的所有 char* 指针都是相同的，无论它们指向的字符串有多长。

你需要使用 strlen(str)+1 而不是 sizeof(str)+1 来解决这个问题:

d->artist = malloc(strlen(s->artist) + 1) ;
strcpy(d->artist, s->artist) ;

d->title = malloc(strlen(s->title) + 1) ;
strcpy(d->title, s->title) ;