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Debugging Valgrind in C

I am still learning valgrind and c. How do I remove "Invalid Free ()"?

Mistake:

==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)
.......

code:

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;
}

I added free(s);

and s=NULL;

andif(s == NULL)..

structure:

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

So, I'm not really sure how I would go about solving this problem?

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1 answer


Basically call songDelete( &song1 );

and change songDelete to:

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;
}


This will allow you to actually force the variable into main

, for example song1

, to actually set to NULL after it is freed.

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