RFDiscussion: Macros used throughout gcc but not defined anywhere

[Zack Weinberg <zack at codesourcery dot com>]

Attached to this message is a huge list of macros used throughout gcc
but not, as far as I can tell, defined anywhere.  The script that
generated this list is limited to checking #if/#ifdef/#ifndef for
uses, so it is not an exhaustive list; nor is it aware of macros
defined by the Makefile, system headers, or compiler.  I have made an
effort to remove false positives, but there may still be a few.  In
some cases I left entries even though I knew or suspected that the
macro was defined by one of these, if I thought the usage was bogus.

Some of these delimit debugging code.  Do we have a policy on the
inclusion of #ifdef-ed debugging code?  I am inclined to say that it
should be accessible at run time if that makes sense, and removed
otherwise. 

I would appreciate comments, in particular pointing out macros that
really are defined somewhere, left for future expansion, or otherwise
should not be removed.

Thanks to Stian Skjelstad <stian@nixia.no> for writing the original
version of the script I used.

zw

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