CODEWITHSUNDEEP
cmacros
user1973900
user1973900

Reputation: 381

c macro, token pasting without quotes

I need to generate some variable name with macro in C. It seems that # token-pasting operator does the job, but the result is always a string.

#define     create_var( name )  char #name

will not work because name is expanding in "name" (as string).

#define     create_var( name )  char prefix##name

will work, but all my vars will have a prefix.

Is there any trick available to obtain a simple name?

create(test) to expand in

char test;

Thanks very much in advance,

Upvotes: 1

Views: 2217

Answers (1)

Johannes Overmann
Johannes Overmann

Reputation: 5151

If you would like your variable name to appear unmodified (without prefix) in your preprocessed code, just use the formal parameter name of the macro, without # and without ##.

You can use # in the macro definition if you want to convert some argument to a string constant. And you can use ## to concatenate tokens to build new tokens (for example to build new variable names with prefixes and/or suffixes and other stuff). With out any of these the preprocessor will just insert the sequence of tokens passed to the macro unmodified (*).

(*): C preprocessor semantics are subtle. Preprocessor macros are replaced at multiple stages during macro expansion which can have quite unobvious results.

Upvotes: 3

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