[PATCH] detect incompatible aliases (PR c/81854)

[Joseph Myers]

On Mon, 18 Sep 2017, Martin Sebor wrote:

> It's meant as an escape hatch.  It allows declaring compatibility
> symbols, for example by the libstdc++ _GLIBCXX_3_4_SYMVER macro
> defined in libstdc++-v3/src/c++98/compatibility.cc.  The macro is
> used to declare compatibility functions of all sorts of incompatible
> types.  The originally posted patch had libstdc++ disable the warning
> for the file with the symbols but Jonathan preferred this solution.
> 
> It could perhaps be tightened up to detect some of the cases on your
> list but I'm not sure it's worth the effort and added complexity.
> Let me know if you feel differently (or have a different suggestion),
> otherwise I will go ahead and commit the patch as is.

Please add a comment explaining this reasoning and commit the patch.

-- 
Joseph S. Myers
joseph@codesourcery.com