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

[Alp Toker]

On 09/05/2014 23:05, Richard Smith wrote:
> On Fri, May 9, 2014 at 10:55 AM, Reid Kleckner <rnk at google.com 
> <mailto:rnk at google.com>> wrote:
>
>     They are exposed:
>     http://clang.llvm.org/docs/LanguageExtensions.html#checked-arithmetic-builtins
>
>     ... but that's not indexed by Google.  Maybe this is the problem?
>     http://clang.llvm.org/robots.txt:
>     User-agent: *
>     Disallow:
>
>
> That's an 'allow everything' robots.txt. The results are there; try 
> searching for: "__builtin_uadd_overflow" clang

I've found Bing yields *far* better results for compiler-related 
technical searches. Definitely worth changing habits and checking out 
for a few days:

   http://www.bing.com/search?q=builtin_uadd_overflow (54 results)

   https://www.google.com/#q=builtin_uadd_overflow (0 results)

I'm not sure why but Google search seems to expect an exact match for 
many of the constructs one encounters in C and C++ so you rarely get 
pertinent results. I was talking with a Google search engineer and they 
said their focus is on the most popular consumer searches so perhaps 
that's the reason.

Cheers
Alp.


>     On Fri, May 9, 2014 at 10:27 AM, Andy Lutomirski
>     <luto at amacapital.net <mailto: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
>         _______________________________________________
>         cfe-dev mailing list
>         cfe-dev at cs.uiuc.edu <mailto:cfe-dev at cs.uiuc.edu>
>         http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
>
>
>
>     _______________________________________________
>     cfe-dev mailing list
>     cfe-dev at cs.uiuc.edu <mailto:cfe-dev at cs.uiuc.edu>
>     http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
>
>
>
>
> _______________________________________________
> cfe-dev mailing list
> cfe-dev at cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev

-- 
http://www.nuanti.com
the browser experts