Freeing memory twicesuggest change
Freeing memory twice is undefined behavior, e.g.
int * x = malloc(sizeof(int)); *x = 9; free(x); free(x);
Quote from standard(18.104.22.168. The free function of C99 ):
Otherwise, if the argument does not match a pointer earlier returned by the calloc, malloc, or realloc function, or if the space has been deallocated by a call to free or realloc, the behavior is undefined.
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