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Cleanup NAN code in float.h, too.

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In the same spirit as 3bf905692, assume that all compilers we still
support provide the NAN macro, and get rid of workarounds for that.

The C standard allows implementations to omit NAN if the underlying
float arithmetic lacks quiet (non-signaling) NaNs.  However, we've
required that feature for years: the workarounds only supported
lack of the macro, not lack of the functionality.  I put in a
compile-time #error if there's no macro, just for clarity.

Also fix up the copies of these functions in ecpglib, and leave
a breadcrumb for the next hacker who touches them.

History of the hacks being removed here can be found in commits
1bc2d544b, 4d17a2146, cec8394b5.

Author: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/1952095.1759764279@sss.pgh.pa.us
This commit is contained in:
Tom Lane
2025-10-08 12:19:53 -04:00
parent 4685977cc5
commit 14ad0d7bf2
2 changed files with 19 additions and 40 deletions
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40
src/include/utils/float.h
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@@ -25,13 +25,6 @@
/* Radians per degree, a.k.a. PI / 180 */
#define RADIANS_PER_DEGREE 0.0174532925199432957692
/* Visual C++ etc lacks NAN, and won't accept 0.0/0.0. */
#if defined(WIN32) && !defined(NAN)
static const uint32 nan[2] = {0xffffffff, 0x7fffffff};
#define NAN (*(const float8 *) nan)
#endif
extern PGDLLIMPORT int extra_float_digits;
/*
@@ -51,6 +44,16 @@ extern char *float8out_internal(float8 num);
extern int float4_cmp_internal(float4 a, float4 b);
extern int float8_cmp_internal(float8 a, float8 b);
/*
* Postgres requires IEEE-standard float arithmetic, including infinities
* and NaNs. We used to support pre-C99 compilers on which <math.h> might
* not supply the standard macros INFINITY and NAN. We no longer do so,
* but these wrapper functions are still preferred over using those macros
* directly.
*
* If you change these functions, see copies in interfaces/ecpg/ecpglib/data.c.
*/
static inline float4
get_float4_infinity(void)
{
@@ -65,36 +68,23 @@ get_float8_infinity(void)
return (float8) INFINITY;
}
/*
* Routines to provide reasonably platform-independent handling of NaN
*
* We assume that isnan() is available and work per spec. However, generating
* a NaN in the first place is less well standardized; pre-C99 systems tend
* not to have C99's NaN macro. We centralize our workaround for this here.
*/
/* The C standard allows implementations to omit NAN, but we don't */
#ifndef NAN
#error "Postgres requires support for IEEE quiet NaNs"
#endif
static inline float4
get_float4_nan(void)
{
#ifdef NAN
/* C99 standard way */
return (float4) NAN;
#else
/* Assume we can get a NAN via zero divide */
return (float4) (0.0 / 0.0);
#endif
}
static inline float8
get_float8_nan(void)
{
/* (float8) NAN doesn't work on some NetBSD/MIPS releases */
#if defined(NAN) && !(defined(__NetBSD__) && defined(__mips__))
/* C99 standard way */
return (float8) NAN;
#else
/* Assume we can get a NaN via zero divide */
return (float8) (0.0 / 0.0);
#endif
}
/*