Printing something with C preprocessor

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Is there a portable way to print a message from the C preprocessor?

When navigating through a large code base, it is sometimes difficult to guess what is defined and what is not. Therefore, I want to print something at compilation time. For example:

#ifdef SOME_DEFINE
// I want a preprocessor to print something here so that 
//  I can know whether SOME_DEFINE is defined or not
#endif

Is this possible to do with C?
I saw something called #error somewhere. Maybe that is my only option, or not?

lots of questions about this already: http://stackoverflow.com/questions/3826832/is-there-a-portable-way-to-print-a-message-from-the-c-preprocessor — pb2q, Jun 05 '12 at 18:03
Better than `#error` is `#warning`, if the preprocessor supports it. — Daniel Fischer, Jun 05 '12 at 18:18

Ruben · Answer 1 · 2012-06-05T18:33:00.207

1

For MS Visual C++:

#define __PRINT(str) __pragma(message(str))

edited Jun 05 '12 at 18:33

answered Jun 05 '12 at 18:13

Ruben

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score 1 · Answer 2 · answered Jun 05 '12 at 19:02

The great thing about the #error directive is that it works even if it is not supported!

If it's supported, the compiler tells you "error: #error" and if it is not supported, the compiler tells you "invalid preprocessing directive". Either way it's a fatal error and compilation stops, and the compiler tells you which was the offending line.

Printing something with C preprocessor

2 Answers2