How to obtain debug/release conditional compiling in C++ program

Question

In a large C++/Qt/QMake/qtcreator project I would like to perform some tests, but only when I am compiling with the debug flag.

Is there a way to tell g++ that some small parts of the code have to be compiled only in debug mode ?

Answer 1

The standard way to do this is to depend on the macro NDEBUG, which is used by the macro assert() defined in <cassert>:

#ifdef NDEBUG
  // release mode code
#else
  // debug mode code
#endif

The opposite of #ifdef is #ifndef, and of course #else branches are optional.

If this macro doesn't work (for whatever reason), you

1. can try the macro QT_NO_DEBUG, which Qt uses for a similar purpose with Q_ASSERT(); and

2. should fix it so that NDEBUG is (un)defined correctly; it's required for <cassert> to work properly, and code you use may depend on it.