The TRACE Macro

This topic applies to:

Edition	Visual Basic	C#	F#	C++	Web Developer
Express				Native only
Pro, Premium, and Ultimate				Native only

To display messages from your program in the debugger Output window, you can use the ATLTRACE macro or the MFC TRACE macro. Like assertions, the trace macros are active only in the Debug version of your program and disappear when compiled in the Release version.

The following examples show some of the ways you can use the TRACE macro. Like printf, the TRACE macro can handle a number of arguments.

int x = 1;
int y = 16;
float z = 32.0;
TRACE( "This is a TRACE statement\n" );

TRACE( "The value of x is %d\n", x );

TRACE( "x = %d and y = %d\n", x, y );

TRACE( "x = %d and y = %x and z = %f\n", x, y, z );

The TRACE macro appropriately handles both char* and wchar_t* parameters. The following examples demonstrate the use of the TRACE macro together with different types of string parameters.

TRACE( "This is a test of the TRACE macro that uses an ANSI string: %s %d\n", "The number is:", 2);

TRACE( L"This is a test of the TRACE macro that uses a UNICODE string: %s %d\n", L"The number is:", 2);

TRACE( _T("This is a test of the TRACE macro that uses a TCHAR string: %s %d\n"), _T("The number is:"), 2);

For more information on the TRACE macro, see Diagnostic Services.

See Also

Other Resources

MFC Debugging Techniques