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 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 September 2015