Question

struct str {
uint8_t *data;
};

int main() {
    struct str *buffer;
    free(buffer->data);
}

How to right check data before use free ? This example call Segmentation failed …

Answer 1

This is because your data has not been allocated. You only create a pointer on a struct str. The correct use is the following:

int main() {
  struct str *buffer = (struct str*)malloc(sizeof(struct str));
  if (buffer == NULL) { fprintf(stderr, "Error with malloc\n"); exit (EXIT_FAILURE); }
  buffer->data = (uint8_t*)malloc(sizeof uint8_t);
  if (buffer->data == NULL) { fprintf(stderr, "Error with malloc\n"); exit (EXIT_FAILURE); }
  // Process data here
  free(buffer->data);
  free(buffer);
  return 0;
}