Thread: Common header file for multiple modules

If one is going to use local macros in the .c module, where does the discipline need to placed?
Is it in being cognizant of the scope of the definitions?
Or in the names of the definitions, making them all unique?

If one is cognizant of the scope, the the names should not matter.
If the names are unique, the scope should not matter.

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Originally Posted by grumpy

You're using the same macro name, but with a different expansion (value) in different translation units?

It is a potential problem if two translation units interact (for example, one calls functions in the other) and each has that macro with a different value. Another way is if a person updates the expansion in one translation unit but not in the other, but expects the update to flow through. Errors can result whether the macro expansion involves code or values.

Of course, both of those potential problems can be reduced by being careful. But, as a rule of thumb, your code will be more reliable if it doesn't rely on that. Even careful people make mistakes, not everyone is careful, and people over-estimate their ability to be careful.

The modules do not interact, and the only one that might update things is myself. So those are not serious concerns in this particular project.

But I am interested in producing proper and acceptable code also.

How might a function call between modules cause a problem?
Is it the assumption of the same defined value incorporated into the return value from a function in the other module? (hope that makes sense)

I have a need for a fair number of macro values, for things like bitmap dimensions and x, y offsets for those bitmaps. These are all similar in purpose
from module to module, but differ in value. My idea right now for handling these is to make their names nondescriptive aside from their function.
Very much like a local loop counter is simply "n" or "i", my defined names might be "DOTX"' and "DOTY", for x and y offsets in each module.

What I am really trying to do is eliminate "magic numbers", but at the same reducing the number of macro names. Is there no good way to do this?

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