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38 lines
767 B
C
38 lines
767 B
C
/* this header file comes from libowfat, http://www.fefe.de/libowfat/ */
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#ifndef ISSET_H
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#define ISSET_H
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/*
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How to check whether a preprocessor symbol is defined or not?
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Difficulty: it should work both in the preprocessor:
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#if is_set(FOO)
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and in C code (and then no code should be generated)
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if (is_set(FOO))
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We will allow both
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#define FOO
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and
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#define FOO 1
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*/
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/* Original question posed by Linus Torvalds
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* https://plus.google.com/102150693225130002912/posts/9gntjh57dXt
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* Solution by comex
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* https://gist.github.com/2365372
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*/
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#define is_set(macro) is_set_(macro)
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#define macrotest_1 ,
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#define macrotest_ ,
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#define is_set_(value) is_set__(macrotest_##value)
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#define is_set__(comma) is_set___(comma 1, 0)
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#define is_set___(_, v, ...) v
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#endif
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