[cfe-dev] Feature request: C intrinsics for overflow detection

Stephen Canon scanon at apple.com
Fri May 9 10:52:52 PDT 2014


You mean something like the __builtin_[u]add[ll]_overflow intrinsics?

– Steve

On May 9, 2014, at 1:27 PM, Andy Lutomirski <luto at amacapital.net> wrote:

> LLVM has the llvm.*.with.overflow.* intrinsics.  Can these be exposed
> to C code?  I imagine this would be straightforward, aside from the
> obligatory bikeshedding about exactly what the interface should be.
> 
> This would eliminate a lot of nasty hacks used to check for overflow,
> especially for multiplication overflow.  I currently write this stuff
> in inline x86 assembler -- ugh!  And maybe gcc would go along if clang
> paved the way :)
> 
> --Andy
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