MS VS 2010 C++ project - how to define DEBUG var?

When you select the DEBUG (as opposed to RELEASE) build then it is already defined for you.

>>Where it prints?

If you use a TRACE command it prints to the output window (which is in visual studio)

How to use Trace command?

eg.
      TRACE(_T("In put your function/class/whatever here"));

or
        TRACE(s);  //s is a string variable, eg with the value of some other variable in it

The question was related to
# ifdef DEBUG

and in the source I have already debugging printings like
DEBUG_PRINT1 ...

and others.

So the question is how should I compile and run this code in Visual Studio 2010 to see the existing printing and not adding new TRACEs?

Build it as a debug build (see my original comment).

I don't see "Active Debug".

What should I do?

See attachment.
vs2010-no-active-debug.png

In my snapshot there are only two project configurations defined.  Debug and Release.  That show the currently selected (=active) one is debug.

Dear, if I need something define or add, please advice how.

I simply wants that in the lib code I compile and run get debugging printing, using already existing in the code

# ifdef DEBUG
.....

DEBUG_PRINT1 ...

and others.

I attached lib code to the original question.

Please advice.

But how to define DEBUG not from code, but compile variable?

You can't.
It is a compiler directive to modify how code is compiled.

such precompiler directive should be pass from outside of code by compiler.
in Linux there is something -D<var>  can I do such thing in Win?

You can define things in the command line to the compiler BUT it is not a variable.  They determine which blocks of code are compiled or not.  (See the project settings).

checking the solution