Can I use an ifdef in a #define line ...

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Can I use an #ifdef in a #define line, to define something two different ways, like this?
#define a b \
#ifdef whatever
c d
#else
e f g
#endif

✍: Guest

No. You can't ``run the preprocessor on itself,'' so to speak. What you can do is use one of two completely separate #define lines, depending on the #ifdef setting:

#ifdef whatever
#define a b c d
#else
#define a b e f g
#endif

2016-02-03, 1110👍, 0💬

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Can I use an ifdef in a #define line ...
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I am including the right header file for the library function I am using, but the linker keeps saying its undefined.
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Is there anything like an ifdef for typedefs?
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Does the sizeof operator work in preprocessor if directives?
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How can I list all of the predefined identifiers?
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I mm compiling a program, and I seem to be missing one of the header files it requires
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