On 01.10.2015 23:45, Alexander Cherepanov wrote:
On 2015-09-17 12:40, Mark Wielaard wrote:
>>* Now const size_t is used instead of const int for malloc argument
>>type.
>
>Thanks. I am still interested in the overflow issue. I believe since we
>are using unsigned arithmetic and we know the size is always > 0, it
>should be as simple as doing:
>
> const size_t elem_size = ... sizeof (...);
> const size_t bytes = num * elem_size;
> if (unlikely (bytes / elem_size != num))
> return E_NOMEM;
> ... malloc (bytes);
Sorry, I'm late to the party but why not check it before multiplication
in a usual way:
if (num > SIZE_MAX / elem_size)
return E_NOMEM;
IIUC elem_size is a compile time constant so the whole division is
computed by compiler.
I had not thought of that. Yes, that is a nicer check.
Thanks,
Mark