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Add __generic(), to be able to use a very simple _Generic().

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Already introducing this allows us to be forward compatible with C11
compilers. By implementing <tgmath.h> on top of this interface, it
becomes trivial to support both our existing GCC and newer compilers.
This commit is contained in:
Ed Schouten 2012-01-05 10:43:03 +00:00
parent a9e4a4780a
commit f8fd121ca4
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=229574
1 changed files with 18 additions and 0 deletions
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18
sys/sys/cdefs.h
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@ -248,6 +248,24 @@
#endif
#endif
/*
* Emulation of C11 _Generic(). Unlike the previously defined C11
* keywords, it is not possible to implement this using exactly the same
* syntax. Therefore implement something similar under the name
* __generic(). Unlike _Generic(), this macro can only distinguish
* between a single type, so it requires nested invocations to
* distinguish multiple cases.
*/
#if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L
#define __generic(expr, t, yes, no) \
_Generic(expr, t: yes, default: no)
#elif __GNUC_PREREQ__(3, 1)
#define __generic(expr, t, yes, no) \
__builtin_choose_expr( \
__builtin_types_compatible_p(__typeof(expr), t), yes, no)
#endif
#if __GNUC_PREREQ__(2, 96)
#define __malloc_like __attribute__((__malloc__))
#define __pure __attribute__((__pure__))