Metashell provides a compile-time debugger for debugging template instantiations and macro usage.

Metashell 4.0.0 is available

From the website:

Some of the major new features in 4.0.0:

• The template debugger supports the Templight patch already merged into Clang (7.0.0), therefore it does not require custom Clang builds.
• Preprocessor shell support for GCC, MSVC and Boost.Wave
• PDB, the preprocessor debugger (similar to MDB, the template debugger)
• Using different configs in Metashell (for testing the same templates/macros with different compilers)

The full list of changes can be found here.

An online demo can be found at http://metashell.org/about/demo/

Installers can be downloaded from http://metashell.org/getting_metashell/installers#version-400