調試Valgrind in C

Question

我仍在學習valgrind和c。我如何消除「無效的免費（）」？

錯誤：

==31415== Invalid free()/delete/delete[]/realloc() 
==31415== at 0x4C2BDEC: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) 
==31415== by 0x400EE1: songDelete (song.c:44) 
==31415== by 0x400B70: main (songtest.c:117) 
==31415== Address 0x51fd9f0 is 0 bytes inside a block of size 14 free'd 
==31415== at 0x4C2BDEC: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) 
==31415== by 0x400EE1: songDelete (song.c:44) 
==31415== by 0x400AD3: main (songtest.c:105) 
....... 

代碼：

void songDelete(song *s) 
{ 
    if(s == NULL){ 
     return; 
    } 

    //artist 
    free(s->artist) ; 
    //title 
    free(s->title) ; 
    //time 
    if(NULL != s->lastPlayed) 
     mtimeDelete(s->lastPlayed) ; 
    //song 
    free(s) ; 
    s = NULL; 
} 

我加入free(s);和s=NULL;和if(s == NULL)..

結構：

typedef struct song_{ 
    char *artist; 
    char *title; 
    mtime *lastPlayed; 
}song; 

所以我不太清楚我會如何解決這個問題？

Answer 1

在主，叫songDelete(&song1);並更改songDelete到：

void songDelete(song **s) 
{ 
    if(*s == NULL){ 
     return; 
    } 

    //artist 
    free((*s)->artist) ; 
    //title 
    free((*s)->title) ; 
    //time 
    if(NULL != (*s)->lastPlayed) 
     mtimeDelete((*s)->lastPlayed) ; 
    //song 
    free(*s) ; 
    *s = NULL; 
} 

這將讓你真正引起main變量，如song1實際上被設置爲NULL釋放之後。