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
  • 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.