RFC: fixing signal context namespace issues

[Zack Weinberg]

On Tue, May 2, 2017 at 11:38 AM, Joseph Myers <joseph@codesourcery.com> wrote:
> Various of the remaining miscellaneous XFAILed conform/ tests are for
> namespace issues in signal.h, sys/wait.h and ucontext.h.

Without commenting on anything else ...

> Note the caveats on platforms using "typedef struct sigcontext
> mcontext_t;": (a) as sigcontext is not a reserved name, the C++ mangled
> name of mcontext_t would change depending on __USE_MISC,

... that sounds like an unacceptable side effect to me.  I would make
the strong claim that the C++ mangled name of a type must never change
in response to any user-controlled feature-selection macro, except
those that have the specific function of selecting alternative
definitions of a particular type (e.g. __USE_FILE_OFFSET64).

zw