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.
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
.