Left shift of negative value

Martin Sebor msebor@gmail.com
Tue Dec 1 17:11:00 GMT 2015


On 12/01/2015 09:07 AM, Andrew Haley wrote:
> Do we support left shift of a negative value?  Technically it's
> undefined and ubsan warns about it.  However, a ton of software would
> surely break if we didn't do the obvious right thing.  I can't find
> anything in the GCC manual.
>

I believe gcc does the expected thing but see bug 65179:
   http://gcc.gnu.org/bugzilla/show_bug.cgi?id=65179

There have been discussions on gcc-patches about some of
the issues the warning has exposed (real or otherwise),
for example:

https://gcc.gnu.org/ml/gcc-patches/2015-05/msg00696.html

Martin



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