= 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.

This program knows how to ignore a large number of guard symbols that
are conventional parts of, .e.g. POSIX, and would only 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.

Finally: if you need this, you may want to look up "auotdafe", a
more evolved and spefic tool I wrote fpr replacing aotoconf-based
builds.

