CODEWITHSUNDEEP
cmacros
radj
radj

Reputation: 4377

What concept is being exhibited in this macro wrapping?

A bunch of code just got handed over to me and I got baffled by macros in the header. I could not understand what they are for:

#define WRAPPER_MACRO(symbol) symbol
#define ANOTHER_SYMBOL WRAPPER_MACRO(ANOTHER_SYMBOL)
#define PREFIXED_ANOTHER_SYMBOL WRAPPER_MACRO(PFX_ANOTHER_SYMBOL)

Why do this? What is the benefit?

Edit: This is not the actual verbatim code from my codebase but it has the same template. I just replaced macro names.

Upvotes: 0

Views: 68

Answers (1)

cf-
cf-

Reputation: 8866

As @Michael said, we'll need to see the real macros to know for sure. But without them, I'm willing to take a few guesses that might help you out.

The macro nesting is probably a stringification thing. This bit of code is from a codebase I maintain:

// As per http://gcc.gnu.org/onlinedocs/cpp/Stringification.html:
// "If you want to stringify the result of expansion of a macro argument, you
// have to use two levels of macros."
#ifndef STRINGIFY
#define STRINGIFY(s) TOSTRING(s)
#define TOSTRING(s) #s
#endif

I'm also guessing your PREFIXED_ANOTHER_SYMBOL macro is doing something similar to this, using the # or ## preprocessor directives to prepend a certain symbol to whatever you feed the macro.

Upvotes: 1

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