[C++ Patch] PR 82466 ("Missing warning for re-declaration of built-in function as variable")

[Paolo Carlini <paolo dot carlini at oracle dot com>]

Hi,

this issue filed by Bernd is sort-of a small follow-up to his c++/71973: 
the C front-end already warns for things like:

    int printf;

where we are declaring in the global namespace a built-in. Beyond 
copying over to the C++ front-end the code already existing in the C 
front-end, there are a couple of nits: 1- We probably want to enable 
suppressing the warning, give it a name, for this I'm overloading the 
name already added by Bernd for c++/71973 (using it in the C front-end 
too, without changes to the default behavior, seems a very safe tweak to 
me); 2- as a pure C++ nit, we probably want to take into account 
namespaces, thus the additional check CP_DECL_CONTEXT (newdecl) == 
global_namespace and the new C++ test (for a couple of hours I had in 
the tree CP_DECL_CONTEXT (newdecl) == CP_DECL_CONTEXT (olddecl), 
probably unnecessarily more verbose!?). What else? A couple of existing 
C++ testcases needed rather obvious adjusting, note in particular 
g++.old-deja/g++.mike/p811.C, which has flattened in the global 
namespace a declaration 'extern ostream clog;', which, were in namespace 
std, as per the standard, would not trigger the new warning, even if 
'clog' is also the name of a math builtin, thanks to the additional 
check mentioned above. Tested x86_64.

Thanks, Paolo.

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