malloc and buffer overflow attacks

[sarn]

On Friday, 31 December 2021 at 00:15:48 UTC, Adam Ruppe wrote:
> On Friday, 31 December 2021 at 00:13:56 UTC, Walter Bright 
> wrote:
>> While D offers buffer overflow detection, it does not protect 
>> against buffer overflows resulting from an array size 
>> calculation overflow:
>>
>>     T* p = cast(T*)malloc(len * T.sizeof);
>
> What I do in D is always slice the malloc to the given size 
> immediately;
>
> T[] p = (cast(T*)malloc(len * T.sizeof))[0 .. len * T.sizepf];
>
> Then you'd get the protection of bounds checking and if you 
> need the ptr, there's still that property.
>
> I'd suggest everyone always do that.

Good thing to do, but Walter's talking about integer overflow 
with the `len * T.sizeof` calculation itself.

calloc() doesn't have this problem.