C preprocessor snippets: Difference between revisions
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#define is_set___(_, v, ...) v
</source>
=== See also ===
* [[X macros]]
* [[incbin()]]
* [[__is_constexpr()]]
[[Category:Programming]]
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Revision as of 14:27, 25 February 2020
Check if a macro is set to 1
This works both in #if
preprocessor expressions and in actual C code:
// https://stackoverflow.com/a/10119699/1697183
// https://news.ycombinator.com/item?id=3830609
// https://github.com/torvalds/linux/commit/69349c2dc01c489eccaa4c472542c08e370c6d7e
#define is_set(macro) is_set_(macro)
#define macrotest_1 ,
#define is_set_(value) is_set__(macrotest_##value)
#define is_set__(comma) is_set___(comma 1, 0)
#define is_set___(_, v, ...) v