174 lines
6.2 KiB
C
174 lines
6.2 KiB
C
/* fenv.h
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This file is part of Cygwin.
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This software is a copyrighted work licensed under the terms of the
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Cygwin license. Please consult the file "CYGWIN_LICENSE" for
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details. */
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#ifndef _FENV_H
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#define _FENV_H 1
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#include <sys/cdefs.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/* Primary sources:
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The Open Group Base Specifications Issue 6:
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http://www.opengroup.org/onlinepubs/000095399/basedefs/fenv.h.html
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C99 Language spec (draft n1256):
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<url unknown>
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Intel(R) 64 and IA-32 Architectures Software Developer's Manuals:
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http://www.intel.com/products/processor/manuals/
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GNU C library manual pages:
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http://www.gnu.org/software/libc/manual/html_node/Control-Functions.html
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http://www.gnu.org/software/libc/manual/html_node/Rounding.html
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http://www.gnu.org/software/libc/manual/html_node/FP-Exceptions.html
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http://www.gnu.org/software/libc/manual/html_node/Status-bit-operations.html
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Linux online man page(s):
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http://linux.die.net/man/3/fegetexcept
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The documentation quotes these sources for reference. All definitions and
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code have been developed solely based on the information from these specs.
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*/
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/* Represents the entire floating-point environment. The floating-point
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environment refers collectively to any floating-point status flags and
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control modes supported by the implementation.
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In this implementation, the struct contains the state information from
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the fstenv/fnstenv instructions and a copy of the SSE MXCSR, since GCC
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uses SSE for a lot of floating-point operations. (Cygwin assumes i686
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or above these days, as does the compiler.) */
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typedef struct _fenv_t
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{
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struct _fpu_env_info {
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unsigned int _fpu_cw; /* low 16 bits only. */
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unsigned int _fpu_sw; /* low 16 bits only. */
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unsigned int _fpu_tagw; /* low 16 bits only. */
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unsigned int _fpu_ipoff;
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unsigned int _fpu_ipsel;
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unsigned int _fpu_opoff;
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unsigned int _fpu_opsel; /* low 16 bits only. */
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} _fpu;
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unsigned int _sse_mxcsr;
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} fenv_t;
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/* Represents the floating-point status flags collectively, including
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any status the implementation associates with the flags. A floating-point
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status flag is a system variable whose value is set (but never cleared)
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when a floating-point exception is raised, which occurs as a side effect
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of exceptional floating-point arithmetic to provide auxiliary information.
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A floating-point control mode is a system variable whose value may be
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set by the user to affect the subsequent behavior of floating-point
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arithmetic. */
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typedef __uint32_t fexcept_t;
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/* The <fenv.h> header shall define the following constants if and only
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if the implementation supports the floating-point exception by means
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of the floating-point functions feclearexcept(), fegetexceptflag(),
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feraiseexcept(), fesetexceptflag(), and fetestexcept(). Each expands to
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an integer constant expression with values such that bitwise-inclusive
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ORs of all combinations of the constants result in distinct values. */
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#define FE_DIVBYZERO (1 << 2)
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#define FE_INEXACT (1 << 5)
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#define FE_INVALID (1 << 0)
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#define FE_OVERFLOW (1 << 3)
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#define FE_UNDERFLOW (1 << 4)
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/* This is not defined by Posix, but since x87 supports it we provide
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a definition according to the same naming scheme used above. */
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#define FE_DENORMAL (1 << 1)
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/* The <fenv.h> header shall define the following constant, which is
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simply the bitwise-inclusive OR of all floating-point exception
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constants defined above: */
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#define FE_ALL_EXCEPT (FE_DIVBYZERO | FE_INEXACT | FE_INVALID \
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| FE_OVERFLOW | FE_UNDERFLOW | FE_DENORMAL)
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/* The <fenv.h> header shall define the following constants if and only
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if the implementation supports getting and setting the represented
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rounding direction by means of the fegetround() and fesetround()
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functions. Each expands to an integer constant expression whose values
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are distinct non-negative vales. */
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#define FE_DOWNWARD (1)
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#define FE_TONEAREST (0)
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#define FE_TOWARDZERO (3)
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#define FE_UPWARD (2)
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/* Precision bit values. Not defined by Posix, but follow logically. */
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#define FE_SINGLEPREC (0)
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#define FE_RESERVEDPREC (1)
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#define FE_DOUBLEPREC (2)
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#define FE_EXTENDEDPREC (3)
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/* The <fenv.h> header shall define the following constant, which
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represents the default floating-point environment (that is, the one
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installed at program startup) and has type pointer to const-qualified
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fenv_t. It can be used as an argument to the functions within the
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<fenv.h> header that manage the floating-point environment. */
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extern const fenv_t *_fe_dfl_env;
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#define FE_DFL_ENV (_fe_dfl_env)
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/* Additional implementation-defined environments, with macro
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definitions beginning with FE_ and an uppercase letter,and having
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type "pointer to const-qualified fenv_t",may also be specified by
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the implementation. */
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#if __GNU_VISIBLE
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/* If possible, the GNU C Library defines a macro FE_NOMASK_ENV which
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represents an environment where every exception raised causes a trap
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to occur. You can test for this macro using #ifdef. It is only defined
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if _GNU_SOURCE is defined. */
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extern const fenv_t *_fe_nomask_env;
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#define FE_NOMASK_ENV (_fe_nomask_env)
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#endif /* __GNU_VISIBLE */
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/* The following shall be declared as functions and may also be
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defined as macros. Function prototypes shall be provided. */
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extern int feclearexcept (int excepts);
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extern int fegetexceptflag (fexcept_t *flagp, int excepts);
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extern int feraiseexcept (int excepts);
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extern int fesetexceptflag (const fexcept_t *flagp, int excepts);
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extern int fetestexcept (int excepts);
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extern int fegetround (void);
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extern int fesetround (int round);
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extern int fegetenv (fenv_t *envp);
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extern int feholdexcept (fenv_t *envp);
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extern int fesetenv (const fenv_t *envp);
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extern int feupdateenv (const fenv_t *envp);
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/* These are not defined in Posix, but make sense by obvious extension. */
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extern int fegetprec (void);
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extern int fesetprec (int prec);
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/* This is Cygwin-custom, not from the standard, for use in the Cygwin CRT. */
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extern void _feinitialise (void);
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/* These are GNU extensions defined in glibc. */
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extern int feenableexcept (int excepts);
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extern int fedisableexcept (int excepts);
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extern int fegetexcept (void);
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#ifdef __cplusplus
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}
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#endif
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#endif /* _FENV_H */
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