Include .cpp instead of header(.h)

Question

There are some cases when we include .cpp file instead of standard header file (.h), for example:

#include \"example.cpp\"

instead of

Answer 1

There are legitimate uses for #include "impl.cpp":

1. testing for access to static/etc variables

2. ad hoc templates like these if c++ template mechanism proves inadequate (rare)

   #define MACRO (...)

   #include "impl.cpp" // uses MACRO

Note that #include "impl.cpp" can be unsafe it same file is included in separate compilation units that are later linked together.