Generating an error if checked boolean macro is not defined

Question

I have several configuration files each one containing the definition of some boolean macro, to be set to 0 or 1. Then, in my code, I check the value of such a macro to deci

Answer 1

The accepted answer of using function-macros is good, but if you want to keep normal macros - and still use the value of FOO if defined and generate an error otherwise you could do:

#if FOO / defined(FOO)
#else
#endif

If FOO is not defined it will trigger integer division by zero.