Evaluate all macros in a C++ header file

Question

I have a requirement to build an automated system to parse a C++ .h file with a lot of #define statements in it and do something with the value that each #def

Answer 1

Here is a concept, based on assumptions from a clarification comment.

• only one header
• no includes
• no dependency on the including code file
• no dependency on previously included headers
• no dependency on include order

Main requirements otherwise:

• do not risk influence on binary build process (being the part which makes the actual software product)
• do not try to emulate the binary build compiler/parser

How to:

• make a copy
• include it from a dedicated code file,
  which only contains "#include "copy.h";
  or directly preprocess the header
  (this just feels weirdly against my habits)
• delete everything except preprocessor and pragmas, paying attention to line-continuation
• replace all "#define"s by "HaPoDefine", except one (e.g. the first)
• repeat
  • preprocess the including code file (most compiler have a switch to do this)
  • save the output
  • turn another "HaPoDefine" back into "#define"
• until no "HaPoDefine" is left
• harvest all macro expansions from the deltas of intermediate saves
• discard everything which is not of relevance
• since the final actual numerical value is most likely a result of the compiler (not the preprocessor), use a tool like bashs "expr" to calculate values for human-eye readability,
  be careful not to risk differences to binary build process
• use some regex magic to achieve any desired format