Yes! It works!

My project.pro is now:

Qt Code:
  1. [...]
  2. CONFIG += qt warn_on debug
  3. [...]
  4. debug {
  5. DEFINES += MY_DEBUG
  6. }
  7. [...]
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and my project.cpp is now:

Qt Code:
  1. #ifdef MY_DEBUG
  2. #define QDEBUG qDebug
  3. #else
  4. #define QDEBUG(fmt,arg...) ((void)0)
  5. #endif
  6. [...]
  7. QDEBUG ( "Value now is %s\n", varResult.ascii() );
  8. [...]
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Thank you very much,
the_bis