C++ vs. AIX -ansi

[David Edelsohn]

>>>>> Mark Mitchell writes:

Mark> This is something of a problem.  V3 doesn't work on lots of systems
Mark> unless you turn on lots of stuff that isn't on by default.  But you
Mark> don't get a chance to turn on until it's potentially "too late".

	I wonder if we should revisit which macros need to be overridden
in os_defines.h because much of the complexity was to handle libio.  Now
that we are not using libio for the moment, we don't need the macros which
libio assumes.

Mark> - Don't define _ANSI_SOURCE on AIX.  (Can we do this in C++, but
Mark> not C?  If we can, do we want to?)

	_ANSI_SOURCE is defined in tm.h CPP_SPEC.  If there is a way to
distinguish the language, we can enable the macro only for C.  Of course
if one preprocessed a file with C and ran the preprocessed output through
C++, things would be wrong.

	We could wrap the _ALL_SOURCE in ifndef _ANSI_C_SOURCE -- a subset
of the logic in AIX's <standards.h> to make sure that additional macros
are not enabled if the user explicitly set some.

David