Re: preprocessor defs on the command line

[Paul Pluzhnikov]

"Chris" <cspears2002@yahoo.com> writes:

> How can I create preprocessor definitions on the command line?  I was
> look at the man pages, but all I found was an option for macros.

Preprocessor definitions and macros are two different names for
the same thing.

Compile your test with:

  g++ -DPI test.cc 
  g++ -UPI test.cc
  g++      test.cc

and observe the differences.

Also note, that the code you wrote is usually written this way instead:

        #ifdef PI
                cout << "PI is defined." << endl;
        #else
                cout << "PI is not defined." << endl;
        #endif

Cheers,
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