[newlib-cygwin] fenv: drop Cygwin-specific implementation in favor of newlib code

[newlib-cygwin] fenv: drop Cygwin-specific implementation in favor of newlib code

[Corinna Vinschen]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=3b22d722555ab88ff4a9181220bbfc3fa59b94ee

commit 3b22d722555ab88ff4a9181220bbfc3fa59b94ee
Author: Corinna Vinschen <corinna@vinschen.de>
Date:   Wed Mar 24 10:58:56 2021 +0100

    fenv: drop Cygwin-specific implementation in favor of newlib code
    
    Drop the Cygwin-specific fenv.cc and fenv.h file and use the equivalent
    newlib functionality now, so we have at least one example of a user for
    this new mechanism.
    
    fenv.c: allow _feinitialise to be called from Cygwin startup code
    
    fenv.h: add declarations for fegetprec and fesetprec for Cygwin only.
            Fix a comment.
    
    Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

Diff:
---
 newlib/libc/machine/shared_x86/sys/fenv.h |  11 +-
 newlib/libm/machine/shared_x86/fenv.c     |   7 +-
 winsup/cygwin/Makefile.in                 |   1 -
 winsup/cygwin/fenv.cc                     | 466 ------------------------------
 winsup/cygwin/include/fenv.h              | 177 ------------
 5 files changed, 16 insertions(+), 646 deletions(-)

diff --git a/newlib/libc/machine/shared_x86/sys/fenv.h b/newlib/libc/machine/shared_x86/sys/fenv.h
index 0cf152a97..e0408fe5b 100644
--- a/newlib/libc/machine/shared_x86/sys/fenv.h
+++ b/newlib/libc/machine/shared_x86/sys/fenv.h
@@ -163,11 +163,20 @@ int fedisableexcept (int __excepts);
 int fegetexcept (void);
 #endif /* __GNU_VISIBLE */
 
+#ifdef __CYGWIN__
+
+#if __MISC_VISIBLE
+int fegetprec (void);
+int fesetprec (int __prec);
+#endif
+
 #ifdef __INSIDE_CYGWIN__
-/* This is Cygwin-custom, not from the standard, for use in the Cygwin CRT.  */
+/* Cygwin-internal ONLY. */
 extern void _feinitialise ();
 #endif
 
+#endif /* __CYGWIN__ */
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/newlib/libm/machine/shared_x86/fenv.c b/newlib/libm/machine/shared_x86/fenv.c
index ccc08e2d8..8d1f1ad7f 100644
--- a/newlib/libm/machine/shared_x86/fenv.c
+++ b/newlib/libm/machine/shared_x86/fenv.c
@@ -63,8 +63,10 @@ static inline bool use_sse(void)
   return false;
 }
 
+#ifndef __CYGWIN__
 /* forward declaration */
 static void _feinitialise (void);
+#endif
 
 /*  This function enables traps for each of the exceptions as indicated
    by the parameter except. The individual exceptions are described in
@@ -449,7 +451,10 @@ fesetprec (int prec)
 #endif
 
 /*  Set up the FPU and SSE environment at the start of execution.  */
-static void
+#ifndef __CYGWIN__
+static
+#endif
+void
 _feinitialise (void)
 {
   extern fenv_t __fe_dfl_env;
diff --git a/winsup/cygwin/Makefile.in b/winsup/cygwin/Makefile.in
index 73d9b37fd..ff6798867 100644
--- a/winsup/cygwin/Makefile.in
+++ b/winsup/cygwin/Makefile.in
@@ -288,7 +288,6 @@ DLL_OFILES:= \
 	exec.o \
 	external.o \
 	fcntl.o \
-	fenv.o \
 	fhandler.o \
 	fhandler_clipboard.o \
 	fhandler_console.o \
diff --git a/winsup/cygwin/fenv.cc b/winsup/cygwin/fenv.cc
deleted file mode 100644
index 69304b513..000000000
--- a/winsup/cygwin/fenv.cc
+++ /dev/null
@@ -1,466 +0,0 @@
-/* fenv.cc
-
-This file is part of Cygwin.
-
-This software is a copyrighted work licensed under the terms of the
-Cygwin license.  Please consult the file "CYGWIN_LICENSE" for
-details. */
-
-#include "winsup.h"
-#include "fenv.h"
-#include "errno.h"
-#include "wincap.h"
-#include <string.h>
-
-/*  x87 supports subnormal numbers so we need it below. */
-#define __FE_DENORM	(1 << 1)
-/* mask (= 0x3f) to disable all exceptions at initialization */
-#define __FE_ALL_EXCEPT_X86 (FE_ALL_EXCEPT | __FE_DENORM)
-
-/*  Mask and shift amount for rounding bits.  */
-#define FE_CW_ROUND_MASK	(0x0c00)
-#define FE_CW_ROUND_SHIFT	(10)
-/*  Same, for SSE MXCSR.  */
-#define FE_MXCSR_ROUND_MASK	(0x6000)
-#define FE_MXCSR_ROUND_SHIFT	(13)
-
-/*  Mask and shift amount for precision bits.  */
-#define FE_CW_PREC_MASK		(0x0300)
-#define FE_CW_PREC_SHIFT	(8)
-
-/*  In x87, exception status bits and mask bits occupy
-   corresponding bit positions in the status and control
-   registers, respectively.  In SSE, they are both located
-   in the control-and-status register, with the status bits
-   corresponding to the x87 positions, and the mask bits
-   shifted by this amount to the left.  */
-#define FE_SSE_EXCEPT_MASK_SHIFT (7)
-
-/* These are writable so we can initialise them at startup.  */
-static fenv_t fe_nomask_env;
-
-/* These pointers provide the outside world with read-only access to them.  */
-const fenv_t *_fe_nomask_env = &fe_nomask_env;
-
-/*  Although Cygwin assumes i686 or above (hence SSE available) these
-   days, and the compiler feels free to use it (depending on compile-
-   time flags of course), we should avoid needlessly breaking any
-   purely integer mode apps (or apps compiled with -mno-sse), so we
-   only manage SSE state in this fenv module if we detect that SSE
-   instructions are available at runtime.  If we didn't do this, all
-   applications run on older machines would bomb out with an invalid
-   instruction exception right at startup; let's not be *that* WJM!  */
-static bool use_sse = false;
-
-/*  This function enables traps for each of the exceptions as indicated
-   by the parameter except. The individual exceptions are described in
-   [ ... glibc manual xref elided ...]. Only the specified exceptions are
-   enabled, the status of the other exceptions is not changed.
-    The function returns the previous enabled exceptions in case the
-   operation was successful, -1 otherwise.  */
-int
-feenableexcept (int excepts)
-{
-  unsigned short cw, old_cw;
-  unsigned int mxcsr = 0;
-
-  if (excepts & ~FE_ALL_EXCEPT)
-    return -1;
-
-  /* Get control words.  */
-  __asm__ volatile ("fnstcw %0" : "=m" (old_cw) : );
-  if (use_sse)
-    __asm__ volatile ("stmxcsr %0" : "=m" (mxcsr) : );
-
-  /* Enable exceptions by clearing mask bits.  */
-  cw = old_cw & ~excepts;
-  mxcsr &= ~(excepts << FE_SSE_EXCEPT_MASK_SHIFT);
-
-  /* Store updated control words.  */
-  __asm__ volatile ("fldcw %0" :: "m" (cw));
-  if (use_sse)
-    __asm__ volatile ("ldmxcsr %0" :: "m" (mxcsr));
-
-  /* Return old value.  We assume SSE and x87 stay in sync.  Note that
-     we are returning a mask of enabled exceptions, which is the opposite
-     of the flags in the register, which are set to disable (mask) their
-     related exceptions.  */
-  return (~old_cw) & FE_ALL_EXCEPT;
-}
-
-/*  This function disables traps for each of the exceptions as indicated
-   by the parameter except. The individual exceptions are described in
-   [ ... glibc manual xref elided ...]. Only the specified exceptions are
-   disabled, the status of the other exceptions is not changed.
-    The function returns the previous enabled exceptions in case the
-   operation was successful, -1 otherwise.  */
-int
-fedisableexcept (int excepts)
-{
-  unsigned short cw, old_cw;
-  unsigned int mxcsr = 0;
-
-  if (excepts & ~FE_ALL_EXCEPT)
-    return -1;
-
-  /* Get control words.  */
-  __asm__ volatile ("fnstcw %0" : "=m" (old_cw) : );
-  if (use_sse)
-    __asm__ volatile ("stmxcsr %0" : "=m" (mxcsr) : );
-
-  /* Disable exceptions by setting mask bits.  */
-  cw = old_cw | excepts;
-  mxcsr |= (excepts << FE_SSE_EXCEPT_MASK_SHIFT);
-
-  /* Store updated control words.  */
-  __asm__ volatile ("fldcw %0" :: "m" (cw));
-  if (use_sse)
-    __asm__ volatile ("ldmxcsr %0" :: "m" (mxcsr));
-
-  /* Return old value.  We assume SSE and x87 stay in sync.  Note that
-     we are returning a mask of enabled exceptions, which is the opposite
-     of the flags in the register, which are set to disable (mask) their
-     related exceptions.  */
-  return (~old_cw) & FE_ALL_EXCEPT;
-}
-
-/*  This function returns a bitmask of all currently enabled exceptions. It
-   returns -1 in case of failure.  */
-int
-fegetexcept (void)
-{
-  unsigned short cw;
-
-  /* Get control word.  We assume SSE and x87 stay in sync.  */
-  __asm__ volatile ("fnstcw %0" : "=m" (cw) : );
-
-  /* Exception is *dis*abled when mask bit is set.  */
-  return (~cw) & FE_ALL_EXCEPT;
-}
-
-/*  Store the floating-point environment in the variable pointed to by envp.
-   The function returns zero in case the operation was successful, a non-zero
-   value otherwise.  */
-int
-fegetenv (fenv_t *envp)
-{
-  /* fnstenv disables all exceptions in the x87 FPU; as this is not what is
-     desired here, reload the cfg saved from the x87 FPU, back to the FPU */
-  __asm__ volatile ("fnstenv %0\n\
-                     fldenv %0"
-		    : "=m" (envp->_fpu) : );
-  if (use_sse)
-    __asm__ volatile ("stmxcsr %0" : "=m" (envp->_sse_mxcsr) : );
-  return 0;
-}
-
-/*  Store the current floating-point environment in the object pointed to
-   by envp. Then clear all exception flags, and set the FPU to trap no
-   exceptions.  Not all FPUs support trapping no exceptions; if feholdexcept
-   cannot set this mode, it returns nonzero value.  If it succeeds, it
-   returns zero.  */
-int
-feholdexcept (fenv_t *envp)
-{
-  unsigned int mxcsr;
-  fegetenv (envp);
-  mxcsr = envp->_sse_mxcsr & ~FE_ALL_EXCEPT;
-  if (use_sse)
-    __asm__ volatile ("ldmxcsr %0" :: "m" (mxcsr));
-  __asm__ volatile ("fnclex");
-  fedisableexcept (FE_ALL_EXCEPT);
-  return 0;
-}
-
-/*  Set the floating-point environment to that described by envp.  The
-   function returns zero in case the operation was successful, a non-zero
-   value otherwise.  */
-int
-fesetenv (const fenv_t *envp)
-{
-  __asm__ volatile ("fldenv %0" :: "m" (envp->_fpu) );
-  if (use_sse)
-    __asm__ volatile ("ldmxcsr %0" :: "m" (envp->_sse_mxcsr));
-  return 0;
-}
-
-/*  Like fesetenv, this function sets the floating-point environment to
-   that described by envp. However, if any exceptions were flagged in the
-   status word before feupdateenv was called, they remain flagged after
-   the call.  In other words, after feupdateenv is called, the status
-   word is the bitwise OR of the previous status word and the one saved
-   in envp.  The function returns zero in case the operation was successful,
-   a non-zero value otherwise.  */
-int
-feupdateenv (const fenv_t *envp)
-{
-  fenv_t envcopy;
-  unsigned int mxcsr = 0;
-  unsigned short sw;
-
-  /* Don't want to modify *envp, but want to update environment atomically,
-     so take a copy and merge the existing exceptions into it.  */
-  memcpy (&envcopy, envp, sizeof *envp);
-  __asm__ volatile ("fnstsw %0" : "=m" (sw) : );
-  if (use_sse)
-    __asm__ volatile ("stmxcsr %0" : "=m" (mxcsr) : );
-  envcopy._fpu._fpu_sw |= (sw & FE_ALL_EXCEPT);
-  envcopy._sse_mxcsr |= (mxcsr & FE_ALL_EXCEPT);
-
-  return fesetenv (&envcopy);
-}
-
-/*  This function clears all of the supported exception flags indicated by
-   excepts.  The function returns zero in case the operation was successful,
-   a non-zero value otherwise.  */
-int
-feclearexcept (int excepts)
-{
-  fenv_t fenv;
-
-  if (excepts & ~FE_ALL_EXCEPT)
-    return EINVAL;
-
-  /* Need to save/restore whole environment to modify status word.  */
-  fegetenv (&fenv);
-
-  /* Mask undesired bits out.  */
-  fenv._fpu._fpu_sw &= ~excepts;
-  fenv._sse_mxcsr &= ~excepts;
-
-  /* Set back into FPU state.  */
-  return fesetenv (&fenv);
-}
-
-/*  This function raises the supported exceptions indicated by
-   excepts.  If more than one exception bit in excepts is set the order
-   in which the exceptions are raised is undefined except that overflow
-   (FE_OVERFLOW) or underflow (FE_UNDERFLOW) are raised before inexact
-   (FE_INEXACT). Whether for overflow or underflow the inexact exception
-   is also raised is also implementation dependent.  The function returns
-   zero in case the operation was successful, a non-zero value otherwise.  */
-int
-feraiseexcept (int excepts)
-{
-  fenv_t fenv;
-
-  if (excepts & ~FE_ALL_EXCEPT)
-    return EINVAL;
-
-  /* Need to save/restore whole environment to modify status word.  */
-  __asm__ volatile ("fnstenv %0" : "=m" (fenv) : );
-
-  /* Set desired exception bits.  */
-  fenv._fpu._fpu_sw |= excepts;
-
-  /* Set back into FPU state.  */
-  __asm__ volatile ("fldenv %0" :: "m" (fenv));
-
-  /* And trigger them - whichever are unmasked.  */
-  __asm__ volatile ("fwait");
-
-  return 0;
-}
-
-/*  Test whether the exception flags indicated by the parameter except
-   are currently set. If any of them are, a nonzero value is returned
-   which specifies which exceptions are set. Otherwise the result is zero.  */
-int
-fetestexcept (int excepts)
-{
-  unsigned short sw;
-  unsigned int mxcsr = 0;
-
-  if (excepts & ~FE_ALL_EXCEPT)
-    return EINVAL;
-
-  /* Get status registers.  */
-  __asm__ volatile ("fnstsw %0" : "=m" (sw) : );
-  if (use_sse)
-    __asm__ volatile ("stmxcsr %0" : "=m" (mxcsr) : );
-
-  /* Mask undesired bits out and return result.  */
-  return (sw | mxcsr) & excepts;
-}
-/*  This function stores in the variable pointed to by flagp an
-   implementation-defined value representing the current setting of the
-   exception flags indicated by excepts.  The function returns zero in
-   case the operation was successful, a non-zero value otherwise.  */
-int
-fegetexceptflag (fexcept_t *flagp, int excepts)
-{
-  unsigned short sw;
-  unsigned int mxcsr = 0;
-
-  if (excepts & ~FE_ALL_EXCEPT)
-    return EINVAL;
-
-  /* Get status registers.  */
-  __asm__ volatile ("fnstsw %0" : "=m" (sw) : );
-  if (use_sse)
-    __asm__ volatile ("stmxcsr %0" : "=m" (mxcsr) : );
-
-  /* Mask undesired bits out and set result.  */
-  *flagp = (sw | mxcsr) & excepts;
-
-  return 0;
-}
-
-/*  This function restores the flags for the exceptions indicated by
-   excepts to the values stored in the variable pointed to by flagp.  */
-int
-fesetexceptflag (const fexcept_t *flagp, int excepts)
-{
-  fenv_t fenv;
-
-  if (excepts & ~FE_ALL_EXCEPT)
-    return EINVAL;
-
-  /* Need to save/restore whole environment to modify status word.  */
-  fegetenv (&fenv);
-
-  /* Set/Clear desired exception bits.  */
-  fenv._fpu._fpu_sw &= ~excepts;
-  fenv._fpu._fpu_sw |= excepts & *flagp;
-  fenv._sse_mxcsr &= ~excepts;
-  fenv._sse_mxcsr |= excepts & *flagp;
-
-  /* Set back into FPU state.  */
-  return fesetenv (&fenv);
-}
-
-/*  Returns the currently selected rounding mode, represented by one of the
-   values of the defined rounding mode macros.  */
-int
-fegetround (void)
-{
-  unsigned short cw;
-
-  /* Get control word.  We assume SSE and x87 stay in sync.  */
-  __asm__ volatile ("fnstcw %0" : "=m" (cw) : );
-
-  return (cw & FE_CW_ROUND_MASK) >> FE_CW_ROUND_SHIFT;
-}
-
-/*  Changes the currently selected rounding mode to round. If round does
-   not correspond to one of the supported rounding modes nothing is changed.
-   fesetround returns zero if it changed the rounding mode, a nonzero value
-   if the mode is not supported.  */
-int
-fesetround (int round)
-{
-  unsigned short cw;
-  unsigned int mxcsr = 0;
-
-  /* Will succeed for any valid value of the input parameter.  */
-  if (round < FE_TONEAREST || round > FE_TOWARDZERO)
-    return EINVAL;
-
-  /* Get control words.  */
-  __asm__ volatile ("fnstcw %0" : "=m" (cw) : );
-  if (use_sse)
-    __asm__ volatile ("stmxcsr %0" : "=m" (mxcsr) : );
-
-  /* Twiddle bits.  */
-  cw &= ~FE_CW_ROUND_MASK;
-  cw |= (round << FE_CW_ROUND_SHIFT);
-  mxcsr &= ~FE_MXCSR_ROUND_MASK;
-  mxcsr |= (round << FE_MXCSR_ROUND_SHIFT);
-
-  /* Set back into FPU state.  */
-  __asm__ volatile ("fldcw %0" :: "m" (cw));
-  if (use_sse)
-    __asm__ volatile ("ldmxcsr %0" :: "m" (mxcsr));
-
-  /* Indicate success.  */
-  return 0;
-}
-
-/*  Returns the currently selected precision, represented by one of the
-   values of the defined precision macros.  */
-int
-fegetprec (void)
-{
-  unsigned short cw;
-
-  /* Get control word.  */
-  __asm__ volatile ("fnstcw %0" : "=m" (cw) : );
-
-  return (cw & FE_CW_PREC_MASK) >> FE_CW_PREC_SHIFT;
-}
-
-/* http://www.open-std.org/jtc1/sc22//WG14/www/docs/n752.htm:
-
-   The fesetprec function establishes the precision represented by its
-   argument prec.  If the argument does not match a precision macro, the
-   precision is not changed.
-
-   The fesetprec function returns a nonzero value if and only if the
-   argument matches a precision macro (that is, if and only if the requested
-   precision can be established). */
-int
-fesetprec (int prec)
-{
-  unsigned short cw;
-
-  /* Will succeed for any valid value of the input parameter.  */
-  switch (prec)
-    {
-    case FE_FLTPREC:
-    case FE_DBLPREC:
-    case FE_LDBLPREC:
-      break;
-    default:
-      return 0;
-    }
-
-  /* Get control word.  */
-  __asm__ volatile ("fnstcw %0" : "=m" (cw) : );
-
-  /* Twiddle bits.  */
-  cw &= ~FE_CW_PREC_MASK;
-  cw |= (prec << FE_CW_PREC_SHIFT);
-
-  /* Set back into FPU state.  */
-  __asm__ volatile ("fldcw %0" :: "m" (cw));
-
-  /* Indicate success.  */
-  return 1;
-}
-
-/*  Set up the FPU and SSE environment at the start of execution.  */
-void
-_feinitialise (void)
-{
-  unsigned int edx, eax;
-  extern fenv_t __fe_dfl_env;
-
-  /* Check for presence of SSE: invoke CPUID #1, check EDX bit 25.  */
-  eax = 1;
-  __asm__ volatile ("cpuid" : "=d" (edx), "+a" (eax) :: "%ecx", "%ebx");
-  /* If this flag isn't set we'll avoid trying to execute any SSE.  */
-  if ((edx & (1 << 25)) != 0)
-    use_sse = true;
-
-  /* Reset FPU: extended prec, all exceptions cleared and masked off.  */
-  __asm__ volatile ("fninit");
-  /* The default cw value, 0x37f, is rounding mode zero.  The MXCSR has
-     no precision control, so the only thing to do is set the exception
-     mask bits.  */
-
-  /* initialize the MXCSR register: mask all exceptions */
-  unsigned int mxcsr = __FE_ALL_EXCEPT_X86 << FE_SSE_EXCEPT_MASK_SHIFT;
-  if (use_sse)
-    __asm__ volatile ("ldmxcsr %0" :: "m" (mxcsr));
-
-  /* Setup unmasked environment, but leave __FE_DENORM masked.  */
-  feenableexcept (FE_ALL_EXCEPT);
-  fegetenv (&fe_nomask_env);
-
-  /* Restore default exception masking (all masked).  */
-  fedisableexcept (FE_ALL_EXCEPT);
-
-  /* Finally cache state as default environment. */
-  fegetenv (&__fe_dfl_env);
-}
-
diff --git a/winsup/cygwin/include/fenv.h b/winsup/cygwin/include/fenv.h
deleted file mode 100644
index 0f7e07445..000000000
--- a/winsup/cygwin/include/fenv.h
+++ /dev/null
@@ -1,177 +0,0 @@
-/* fenv.h
-
-This file is part of Cygwin.
-
-This software is a copyrighted work licensed under the terms of the
-Cygwin license.  Please consult the file "CYGWIN_LICENSE" for
-details. */
-
-#ifndef _FENV_H
-#define _FENV_H 1
-
-#include <sys/cdefs.h>
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-
-/* Primary sources:
-
-     The Open Group Base Specifications Issue 6:
-   http://www.opengroup.org/onlinepubs/000095399/basedefs/fenv.h.html
-
-     C99 Language spec (draft n1256):
-   <url unknown>
-
-     Intel(R) 64 and IA-32 Architectures Software Developer's Manuals:
-   http://www.intel.com/products/processor/manuals/
-
-     GNU C library manual pages:
-   http://www.gnu.org/software/libc/manual/html_node/Control-Functions.html
-   http://www.gnu.org/software/libc/manual/html_node/Rounding.html
-   http://www.gnu.org/software/libc/manual/html_node/FP-Exceptions.html
-   http://www.gnu.org/software/libc/manual/html_node/Status-bit-operations.html
-
-     Linux online man page(s):
-   http://linux.die.net/man/3/fegetexcept
-
-    The documentation quotes these sources for reference.  All definitions and
-   code have been developed solely based on the information from these specs.
-
-*/
-
-/*  Represents the entire floating-point environment. The floating-point
-   environment refers collectively to any floating-point status flags and
-   control modes supported by the implementation.
-    In this implementation, the struct contains the state information from
-   the fstenv/fnstenv instructions and a copy of the SSE MXCSR, since GCC
-   uses SSE for a lot of floating-point operations.  (Cygwin assumes i686
-   or above these days, as does the compiler.)  */
-
-typedef struct _fenv_t
-{
-  struct _fpu_env_info {
-    unsigned int _fpu_cw;	/* low 16 bits only. */
-    unsigned int _fpu_sw;	/* low 16 bits only. */
-    unsigned int _fpu_tagw;	/* low 16 bits only. */
-    unsigned int _fpu_ipoff;
-    unsigned int _fpu_ipsel;
-    unsigned int _fpu_opoff;
-    unsigned int _fpu_opsel;	/* low 16 bits only. */
-  } _fpu;
-  unsigned int _sse_mxcsr;
-} fenv_t;
-
-/*  Represents the floating-point status flags collectively, including
-   any status the implementation associates with the flags. A floating-point
-   status flag is a system variable whose value is set (but never cleared)
-   when a floating-point exception is raised, which occurs as a side effect
-   of exceptional floating-point arithmetic to provide auxiliary information.
-    A floating-point control mode is a system variable whose value may be
-   set by the user to affect the subsequent behavior of floating-point
-   arithmetic. */
-
-typedef __uint32_t fexcept_t;
-
-/*  The <fenv.h> header shall define the following constants if and only
-   if the implementation supports the floating-point exception by means
-   of the floating-point functions feclearexcept(), fegetexceptflag(),
-   feraiseexcept(), fesetexceptflag(), and fetestexcept(). Each expands to
-   an integer constant expression with values such that bitwise-inclusive
-   ORs of all combinations of the constants result in distinct values.  */
-
-#define FE_DIVBYZERO	(1 << 2)
-#define FE_INEXACT	(1 << 5)
-#define FE_INVALID	(1 << 0)
-#define FE_OVERFLOW	(1 << 3)
-#define FE_UNDERFLOW	(1 << 4)
-
-/*  The <fenv.h> header shall define the following constant, which is
-   simply the bitwise-inclusive OR of all floating-point exception
-   constants defined above:  */
-
-/* in agreement w/ Linux the subnormal exception will always be masked */
-#define FE_ALL_EXCEPT \
-  (FE_INEXACT | FE_UNDERFLOW | FE_OVERFLOW | FE_DIVBYZERO | FE_INVALID)
-
-/*  The <fenv.h> header shall define the following constants if and only
-   if the implementation supports getting and setting the represented
-   rounding direction by means of the fegetround() and fesetround()
-   functions. Each expands to an integer constant expression whose values
-   are distinct non-negative vales.  */
-
-#define FE_DOWNWARD	(1)
-#define FE_TONEAREST	(0)
-#define FE_TOWARDZERO	(3)
-#define FE_UPWARD	(2)
-
-/* Only Solaris and QNX implement fegetprec/fesetprec.  As Solaris, use the
-   values defined by http://www.open-std.org/jtc1/sc22//WG14/www/docs/n752.htm
-   QNX defines different values. */
-#if __MISC_VISIBLE
-#define FE_FLTPREC	(0)
-#define FE_DBLPREC	(2)
-#define FE_LDBLPREC	(3)
-#endif
-
-/*  The <fenv.h> header shall define the following constant, which
-   represents the default floating-point environment (that is, the one
-   installed at program startup) and has type pointer to const-qualified
-   fenv_t. It can be used as an argument to the functions within the
-   <fenv.h> header that manage the floating-point environment.  */
-
-extern const fenv_t *_fe_dfl_env;
-#define FE_DFL_ENV (_fe_dfl_env)
-
-/*  Additional implementation-defined environments, with macro
-   definitions beginning with FE_ and an uppercase letter,and having
-   type "pointer to const-qualified fenv_t",may also be specified by
-   the implementation.  */
-
-#if __GNU_VISIBLE
-/*  If possible, the GNU C Library defines a macro FE_NOMASK_ENV which
-   represents an environment where every exception raised causes a trap
-   to occur. You can test for this macro using #ifdef. It is only defined
-   if _GNU_SOURCE is defined.  */
-extern const fenv_t *_fe_nomask_env;
-#define FE_NOMASK_ENV (_fe_nomask_env)
-#endif /* __GNU_VISIBLE */
-
-
-/*  The following shall be declared as functions and may also be
-   defined as macros. Function prototypes shall be provided.  */
-extern int feclearexcept (int __excepts);
-extern int fegetexceptflag (fexcept_t *__flagp, int __excepts);
-extern int feraiseexcept (int __excepts);
-extern int fesetexceptflag (const fexcept_t *__flagp, int __excepts);
-extern int fetestexcept (int __excepts);
-extern int fegetround (void);
-extern int fesetround (int __round);
-extern int fegetenv (fenv_t *__envp);
-extern int feholdexcept (fenv_t *__envp);
-extern int fesetenv (const fenv_t *__envp);
-extern int feupdateenv (const fenv_t *__envp);
-
-#if __GNU_VISIBLE
-/* These are GNU extensions defined in glibc.  */
-extern int feenableexcept (int __excepts);
-extern int fedisableexcept (int __excepts);
-extern int fegetexcept (void);
-#endif
-
-#if __MISC_VISIBLE
-extern int fegetprec (void);
-extern int fesetprec (int __prec);
-#endif
-
-#ifdef __INSIDE_CYGWIN__
-/* This is Cygwin-custom, not from the standard, for use in the Cygwin CRT.  */
-extern void _feinitialise ();
-#endif
-
-#ifdef __cplusplus
-}
-#endif
-
-#endif /* _FENV_H */