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Simplify NAN definitions.

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Similar to my patches for HUGE_VAL and INFINITY. this patch eliminates
the bits/nan.h headers.  __builtin_nanf ("") is used to define NAN for
GCC 3.3 and later; the fallback is (0.0f / 0.0f), which is a constant
expression for a quiet NaN of type float, but raises a spurious
"invalid" exception outside static initializers, which seems the best
that can be done purely in standard C.  Again, if anyone actually uses
a compiler with its own incompatible extension for producing a
constant quiet NaN, we can add compiler conditionals.

Tested for x86_64.

	*  math/math.h [__USE_ISOC99] (NAN): Define directly here.  Do not
	include <bits/nan.h>.
	* math/Makefile (headers): Remove bits/nan.h.
	* bits/nan.h: Remove.
	* sysdeps/ieee754/bits/nan.h: Likewise.
	* sysdeps/mips/bits/nan.h: Likewise.
This commit is contained in:
Joseph Myers
2017-08-31 16:39:25 +00:00
parent 5ef1b2138d
commit c0c49d60cf
6 changed files with 16 additions and 127 deletions
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11
math/math.h
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@@ -65,8 +65,15 @@ __BEGIN_DECLS
# define INFINITY HUGE_VALF
# endif
/* Get machine-dependent NAN value (returned for some domain errors). */
# include <bits/nan.h>
/* IEEE Not A Number. */
# if __GNUC_PREREQ (3, 3)
# define NAN (__builtin_nanf (""))
# else
/* This will raise an "invalid" exception outside static initializers,
but is the best that can be done in ISO C while remaining a
constant expression. */
# define NAN (0.0f / 0.0f)
# endif
#endif /* __USE_ISOC99 */
#if __GLIBC_USE (IEC_60559_BFP_EXT)