How to check for overflow when adding/multiplying numbers?

[Ola Fosheim Grøstad]

On Monday, 6 December 2021 at 17:46:35 UTC, Dave P. wrote:
> I’m porting some C code which uses the gcc intrinsics to do a 
> multiply/add with overflow checking. See 
> [here](https://gcc.gnu.org/onlinedocs/gcc/Integer-Overflow-Builtins.html) for reference. Is there a D equivalent?

There is:

https://dlang.org/phobos/core_checkedint.html

I have never used it, so I don't know how well it performs.