On 7/5/2012 3:02 AM, Nathan Ridge wrote:
Hello,
I've noticed preprocessor metaprogramming has become more popular of late, both as a means to provide a cleaner alternative interface to a library (e.g. the DEFINE and ADAPT macros in Boost.Fusion or the proposed macro wrappers for Boost.TypeErasure) and as a means to emulate new language features (e.g. Boost.LocalFunction, Boost.Generic, and Boost.Contract).
Sadly, IDE support for writing macro metaprograms is fairly poor in comparison to IDE support for writing regular C++ code.
I wanted to share with you something I've found very useful for tracing/debugging macro metaprograms: the Eclipse CDT IDE has a "macro stepper" that allows you to step through the expansion of a macro step-by-step from the initial invocation to the final expansion. (This feature can be accessed by using the "Explore Macro Expansion" context menu item on a macro invocation.)
I would be curious to hear what tools you have found useful for writing or debugging macro metaprograms.
The problem with debugging macro expansion is that the preprocessor one is using may be incorrectly expanding a macro and using other tools to look at the macro expansion will not show you the macro expansion which the incorrectly expanding preprocessor is doing. This is particularly the case with VC++. I have already queried on the Microsoft online forums if VC++ has a means of showing macro expansion step-by-step and the answer appears to be that it does not. This is not surprising since such a tool would further highlight VC++'s bugs in macro expansion, which they have pointedly declined to fix for many, many years. Boost already has a solution for viewing macro expansion in a 100% correct C++ preprocessor: Use the Boost wave with the tracing facility. This is very easy to do to see how a macro should be expanded. The Eclipse CDT IDE's "macro stepper" is a welcome edition to how a macro is expanded as long as the Eclipse C++ implementation's preprocessor is a 100% compliant preprocessor.