c - Is it possible to free a char * allocated with a calloc" -

i know if it's possible free char * (string) allocated calloc several times.

char * signal;    (int = 0 ; < n ; i++)  {       signal = (char*) calloc(n, sizeof(char));    if (a = true) {       signal[i] = 1;    }     /* stuff */     free(signal); /* error here : double free or corruption */    } 

why error on free()?

would know if it's possible free char * (string) allocated calloc several times.

short answer: no

long answer: 1 call malloc(), calloc(), realloc(null, ...)^(*1) allows (requires, not leak memory) exactly one call free() passing value latter returned 1 of former.

so, if passing free()ed address free() , assuming had not been returned allocation after previous call free(), code invokes undefined behaviour, can happen on.

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^(*1) notes on realloc():

• successive calls realloc() not passing null not increment sum of necessary calls free(). in other words

  char * p = malloc(42); p = realloc(43); 

  does require one call free()

  free(p); 

• passing null realloc() makes realloc() count call malloc().

  doing

  char * p = realloc(null, 42);  

  is same doing

  char * p = malloc(42);