-mno-wide-multiply
-mwide-multiply
Control whether GNU CC uses the mul and imul that produce 64 bit results in eax:edx from 32 bit operands to do long long multiplies and 32-bit division by constants.

We recommend using calloc(3) whenever allocating multiple objects of the same size. The above code would be written as:

size_t num, size;
char *ptr;
...
if ((ptr = calloc(num, size)) == NULL)
return (NULL);

calloc(3) has checks to make sure the multiplication does not overflow.