[llvm-dev] GCC 5 and -Wstrict-aliasing in JSON.h

Andrew Haley via llvm-dev
Tue, 14 Aug 2018 09:51:16 -0000

On 08/12/2018 02:19 PM, Kim Gräsman wrote:
> I still feel a little uncomfortable, because I think Jonathan makes an
> excellent point -- if GCC thinks there's a strict-aliasing violation
> (whether the standard agrees or not) and classifies this as undefined
> behavior, we might invoke the optimizers wrath. The warning is a nice
> hint that this could happen.

Indeed.  And I'm not convinced that the pointer cast is necessary anyway:
if the type passed in is a union, why not simply take the union member of
the appropriate type?

I don't think that GCC would produce this warning unnecessarily.  You
are in dangerous waters.

--
Andrew Haley
Java Platform Lead Engineer
Red Hat UK Ltd. <https://www.redhat.com>
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