c - Is there a way to both check a macro is defined and it equals a certain value at the same time

Question

I regularly use object-like preprocessor macros as boolean flags in C code to turn on and off sections of code.

For example

#define DEBUG_PRINT 1

And then use it like

#if(DEBUG_PRINT == 1)
    printf("%s", "Testing");
#endif

However, it comes a problem if the header file that contains the #define is forgotten to be included in the source code. Since the macro is not declared, the preprocessor treats it as if it equals 0, and the #if statement never runs.

When the header file is forgotten to be included, non-expected, unruly behaviour can occur.

Ideally, I would like to be able to both check that a macro is defined, and check that it equals a certain value, in one line. If it is not defined, the preprocessor throws an error (or warning).

I'm looking for something along the lines of:

#if-def-and-true-else-throw-error(DEBUG_PRINT)
    ...
#endif

It's like a combination of #ifdef and #if, and if it doesn't exist, uses #error.

I have explored a few avenues, however, preprocessor directives can't be used inside a #define block, and as far as I can tell, there is no preprocessor option to throw errors/warnings if a macro is not defined when used inside a #if statement.

Answer 1

This may not work for the general case (I don't think there's a general solution to what you're asking for), but for your specific example you might consider changing this sequence of code:

#if(DEBUG_PRINT == 1)
    printf("%s", "Testing");
#endif

to:

if (DEBUG_PRINT == 1) {
    printf("%s", "Testing");
}

It's no more verbose and will fail to compile if DEBUG_PRINT is not defined or if it's defined to be something that cannot be compared with 1.