CODEWITHSUNDEEP
cpointersmalloc
jop
jop

Reputation: 121

pointer freed not allocated

when I compile this piece of code, the pointer freed not allocated error pops up. Could someone please explain why that is? Thank you!

static int make_buffer(FILE *input, char *buffer[]){
  *buffer = (char *)malloc(INIT_BUFFER_SIZE*sizeof(char));

  int buffer_size = INIT_BUFFER_SIZE;
  int txt_size = 0;

  char cha;
  while((cha = fgetc(input)) != EOF){
    if (txt_size == buffer_size){
      *buffer = (char *)realloc(buffer, buffer_size*2*sizeof(char));
      buffer_size *= 2;
    }
    (*buffer)[txt_size] = cha;
    txt_size ++;
  }

  free(*buffer);
  return txt_size;
}

Upvotes: 0

Views: 371

Answers (1)

DrC
DrC

Reputation: 7698

It means that the code is attempting to free something that was not allocated using malloc/realloc. In your case, I think the problem is in

*buffer = (char *)realloc(buffer, buffer_size*2*sizeof(char));

which should be

*buffer = realloc(*buffer, buffer_size*2);

Probably also want to check the result of realloc just for form. Note I simplified yours a bit in that sizeof(char) == 1 by definition and the cast shouldn't be needed these days (it used to be). The commend by David S. about the usefulness of freeing the result is also valid.

Upvotes: 2

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