c0b4353654
TS 18661-1 defines a macro FE_SNANS_ALWAYS_SIGNAL in <fenv.h>, to indicate that the recommended practice regarding sNaNs (that operations always produce a qNaN output with "invalid" exception, even in the fmax / fmin / hypot / pow cases where a qNaN input would not result in qNaN output) is followed. Now that those functions with C99 special cases for NaNs have been fixed not to apply those special cases to sNaN, only to qNaN, glibc follows that recommended practice. This patch makes it define the corresponding macro. Since compiler optimizations may affect whether sNaNs behave as expected and the macro relates to both language and library features, it is only defined if __SUPPORT_SNAN__ is defined (which GCC defines for -fsignaling-nans). It is also not defined if FE_INVALID is undefined, since the recommended practice specifically refers to raising the "invalid" exception, so it seems inappropriate to define the macro for soft-float cases without support for exceptions. (Further refinement would be possible in cases where bits/fenv.h is shared by configurations both with and without exceptions support.) Tested for x86_64 and x86, and also did compile-only testing for nios2 to cover the no-exceptions case. * math/fenv.h [__GLIBC_USE (IEC_60559_BFP_EXT) && FE_INVALID && __SUPPORT_SNAN__] (FE_SNANS_ALWAYS_SIGNAL): New macro. * math/test-fe-snans-always-signal.c: New file. * math/Makefile (tests): Add test-fe-snans-always-signal. (CFLAGS-test-fe-snans-always-signal.c): New variable. * manual/arith.texi (Infinity and NaN): Document FE_SNANS_ALWAYS_SIGNAL.
175 lines
5.7 KiB
C
175 lines
5.7 KiB
C
/* Copyright (C) 1997-2016 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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/*
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* ISO C99 7.6: Floating-point environment <fenv.h>
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*/
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#ifndef _FENV_H
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#define _FENV_H 1
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#define __GLIBC_INTERNAL_STARTING_HEADER_IMPLEMENTATION
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#include <bits/libc-header-start.h>
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/* Get the architecture dependend definitions. The following definitions
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are expected to be done:
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fenv_t type for object representing an entire floating-point
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environment
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FE_DFL_ENV macro of type pointer to fenv_t to be used as the argument
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to functions taking an argument of type fenv_t; in this
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case the default environment will be used
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fexcept_t type for object representing the floating-point exception
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flags including status associated with the flags
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femode_t type for object representing floating-point control modes
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FE_DFL_MODE macro of type pointer to const femode_t to be used as the
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argument to fesetmode; in this case the default control
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modes will be used
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The following macros are defined iff the implementation supports this
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kind of exception.
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FE_INEXACT inexact result
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FE_DIVBYZERO division by zero
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FE_UNDERFLOW result not representable due to underflow
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FE_OVERFLOW result not representable due to overflow
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FE_INVALID invalid operation
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FE_ALL_EXCEPT bitwise OR of all supported exceptions
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The next macros are defined iff the appropriate rounding mode is
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supported by the implementation.
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FE_TONEAREST round to nearest
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FE_UPWARD round toward +Inf
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FE_DOWNWARD round toward -Inf
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FE_TOWARDZERO round toward 0
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*/
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#include <bits/fenv.h>
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__BEGIN_DECLS
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/* Floating-point exception handling. */
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/* Clear the supported exceptions represented by EXCEPTS. */
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extern int feclearexcept (int __excepts) __THROW;
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/* Store implementation-defined representation of the exception flags
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indicated by EXCEPTS in the object pointed to by FLAGP. */
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extern int fegetexceptflag (fexcept_t *__flagp, int __excepts) __THROW;
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/* Raise the supported exceptions represented by EXCEPTS. */
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extern int feraiseexcept (int __excepts) __THROW;
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#if __GLIBC_USE (IEC_60559_BFP_EXT)
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/* Set the supported exception flags represented by EXCEPTS, without
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causing enabled traps to be taken. */
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extern int fesetexcept (int __excepts) __THROW;
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#endif
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/* Set complete status for exceptions indicated by EXCEPTS according to
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the representation in the object pointed to by FLAGP. */
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extern int fesetexceptflag (const fexcept_t *__flagp, int __excepts) __THROW;
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/* Determine which of subset of the exceptions specified by EXCEPTS are
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currently set. */
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extern int fetestexcept (int __excepts) __THROW;
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#if __GLIBC_USE (IEC_60559_BFP_EXT)
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/* Determine which of subset of the exceptions specified by EXCEPTS
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are set in *FLAGP. */
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extern int fetestexceptflag (const fexcept_t *__flagp, int __excepts) __THROW;
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#endif
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/* Rounding control. */
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/* Get current rounding direction. */
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extern int fegetround (void) __THROW __attribute_pure__;
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/* Establish the rounding direction represented by ROUND. */
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extern int fesetround (int __rounding_direction) __THROW;
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/* Floating-point environment. */
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/* Store the current floating-point environment in the object pointed
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to by ENVP. */
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extern int fegetenv (fenv_t *__envp) __THROW;
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/* Save the current environment in the object pointed to by ENVP, clear
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exception flags and install a non-stop mode (if available) for all
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exceptions. */
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extern int feholdexcept (fenv_t *__envp) __THROW;
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/* Establish the floating-point environment represented by the object
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pointed to by ENVP. */
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extern int fesetenv (const fenv_t *__envp) __THROW;
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/* Save current exceptions in temporary storage, install environment
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represented by object pointed to by ENVP and raise exceptions
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according to saved exceptions. */
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extern int feupdateenv (const fenv_t *__envp) __THROW;
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/* Control modes. */
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#if __GLIBC_USE (IEC_60559_BFP_EXT)
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/* Store the current floating-point control modes in the object
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pointed to by MODEP. */
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extern int fegetmode (femode_t *__modep) __THROW;
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/* Establish the floating-point control modes represented by the
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object pointed to by MODEP. */
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extern int fesetmode (const femode_t *__modep) __THROW;
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#endif
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/* Include optimization. */
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#ifdef __OPTIMIZE__
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# include <bits/fenvinline.h>
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#endif
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/* NaN support. */
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#if (__GLIBC_USE (IEC_60559_BFP_EXT) \
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&& defined FE_INVALID \
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&& defined __SUPPORT_SNAN__)
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# define FE_SNANS_ALWAYS_SIGNAL 1
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#endif
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#ifdef __USE_GNU
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/* Enable individual exceptions. Will not enable more exceptions than
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EXCEPTS specifies. Returns the previous enabled exceptions if all
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exceptions are successfully set, otherwise returns -1. */
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extern int feenableexcept (int __excepts) __THROW;
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/* Disable individual exceptions. Will not disable more exceptions than
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EXCEPTS specifies. Returns the previous enabled exceptions if all
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exceptions are successfully disabled, otherwise returns -1. */
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extern int fedisableexcept (int __excepts) __THROW;
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/* Return enabled exceptions. */
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extern int fegetexcept (void) __THROW;
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#endif
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__END_DECLS
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#endif /* fenv.h */
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