Messer is an interactive environment for evaluating C preprocessing macros conforming to C++17 standard with showing macro replacement steps.

• You need to install below manually:
  • C++17 supported GNU C++ Compiler < 15
    • NOTE: g++ >= 15 can't build messer. Please use g++ <= 14
  • Boost
    • Boost.Coroutine2
    • Boost.Preprocessor
  • sed
  • awk
  • make
• You can get the following prerequisites as git-submodules:
  • Veiler
  • Linse

$ make 

It takes extremely long time.
For example, it takes 4 minutes to build messer on an AMD Ryzen7 2700X.
It is recommended to take coffee while building.

...patience... ...patience... ...patience... 

You can input programs following the prompt (>>>).
#pragma step tokens shows macro replacement steps for tokens.
You can exit Messer with C-d.

>>> #define CAT_I(a, b) a ## b >>> #define ID(x) x >>> CAT_I(a, ID(b)) aID(b) >>> #pragma step CAT_I(a, ID(b)) CAT_I(a, ID(b)) -> a ## ID(b) -> aID(b) >>> #define CAT(a, b) CAT_I(a, b) >>> CAT(a, ID(b)) ab >>> #pragma step CAT(a, ID(b)) CAT(a, ID(b)) -> CAT_I(a, ID(b)) -> CAT_I(a, b) -> a ## b -> ab >>> 

MIT License (see LICENSE file)

see LICENSES directory.