Overflow traps

[philberty]

GCC has plenty of builtin_overflow functions ADA has overflow traps akin to rust so we should be able to port this function:

https://github.com/Rust-GCC/gccrs/blob/c7275a7fb89f324e7cd7881d12a49287a89f1c74/gcc/ada/gcc-interface/trans.cc#L9531-L9726

[bjorn3]

Does that emit a trap instruction? In rustc with overflow checks enabled the panic handler is called instead. Providing a trap instruction as option in addition to wrapping and calling the panic handler on overflow may be fine though.

[philberty]

I use the word trap, as in to trap the case of when overflow occurs we can amend this to call whatever panic handler we want. I am linking to this code fragment just so we can find the code to call into the internal builtin functions which GCC to get the overflow condition.