ifdex - a tool for excavating configuration macros

The purpose of this tool is to walk through a C codebase and generate
a report listing symbols used as conditionals in #ifdef/#ifndef/#elif
lines.  By default it processes files with the extensions .c, .h, .cpp,
.y, and .l.

Tis program knows how to ignore a large number of guard symbols that
are conventional parts of, .e.g. POSIX, and would on;y add noise to
the report. This filter can be turned off.

This is useful information to have if you are trying to identify
configuration symbols intended to be set by a build system.  The use
case this tool was originally built for was prying 227 KLOC of C loose
from the clammy grip of autoconf.

It's also useful for detecting stray or broken guard symbols.

You can run a simple regression test with 'make check".  Examining
smoketest.tst and smoketest.chk may be instructive.

						Eric S. Raymond
						<esr@thyrsus.com>
						September 2015