cppp is a partial preprocessor for C/C++ code. It implements enough of the C preprocessor to identify the preprocessor statements #if, #ifdef, et al., and applies their effects for the identifiers that are specified on the command-line. Preprocessor statements using identifiers not specified by the user are passed through without modification. And no other part of the input is altered. Thus, if cppp is invoked with the options -DFOO -UBAR, then FOO will be defined, BAR will be undefined, and all other identifiers will be unaffected. A section guarded by "#ifdef FOO" will be included in the output without the guard statements, and a section guarded by "#ifdef BAR" will be entirely dropped from the output. In addition to removing #ifdef statements, cppp understands complex expressions in #if statements that involve the defined operator, and will apply the effects even partially. Thus for example the preprocessor statement "#if (defined(BAR) || defined(BAZ))" would be edited to read "#if defined(BAZ)" in the output. cppp can also handle simple numeric tests. For example, giving cppp the option -D_LIB_VERSION=5 would cause the preprocessor statement "#if _LIB_VERSION >= 4" to succeed. Note, however, that cppp is limited to dealing with integer constants. The preprocessor statement "#if _LIB_VERSION >= _HEADER_FILE_VERSION" would simply get rewritten to "#if 5 >= _HEADER_FILE_VERSION", even if a definition for _HEADER_FILE_VERSION was provided in the same file. cppp assumes that its input files are valid C code. It will only do as much error-checking on the input as it needs to in order to identify the preprocessor directives. When cppp does find an error in an input file, it will output a message and do its best to skip over the invalid construct and continue parsing. Note that it is possible (though rare) for compiler extensions to be reported as errors -- e.g. some compilers reportedly allow #elif directives in a sequence beginning with #ifdef. (Although please note that cppp does include support for #elifdef/#elifndef.) The general purpose of this program is to deal with legacy code bases where #ifdefs have crept in and infiltrated the source. This sort of thing usually happens while code is transitioning from one platform to another, in the misguided belief that this will ease the process rather than make it more confusing. Then, if the time finally comes that the ifdefs can be safely removed, it often doesn't get done because it's too tedious and error-prone to do it manually. I originally wrote cppp as an interesting exercise, but I later wound up using it to save myself from just such a tedious task. Sadly, because the code was not originally intended to be seen by anyone, it is not well-written and in some places it is downright opaque. I have attempted to ameliorate this by cleaning up some of the most egregious inconsistencies and adding a handful of comments, but the central functions are quite large and not easily explicated (particularly with all the intervening years since the time of its original creation). I offer it solely as a tool that might save you from a mind-numbing chore, but not as something to learn from. That said, cppp is free software, so you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but without any warranty; without even the implied warranty of merchantability or fitness for a particular purpose. See the GNU General Public License, included in this distribution in the file COPYING, for more details. cppp website: <http://www.muppetlabs.com/~breadbox/software/cppp.html>. Brian Raiter breadbox@muppetlabs.com June, 2011