libm.h

ecos为实时嵌入式操作系统

#ifndef CYGONCE_PKGCONF_LIBM_H
#define CYGONCE_PKGCONF_LIBM_H
//========================================================================
//
//      libm.h
//
//      Configuration header for mathematical function library
//
//========================================================================
//####COPYRIGHTBEGIN####
//
// -------------------------------------------
// The contents of this file are subject to the Cygnus eCos Public License
// Version 1.0 (the "License"); you may not use this file except in
// compliance with the License.  You may obtain a copy of the License at
// http://sourceware.cygnus.com/ecos
// 
// Software distributed under the License is distributed on an "AS IS"
// basis, WITHOUT WARRANTY OF ANY KIND, either express or implied.  See the
// License for the specific language governing rights and limitations under
// the License.
// 
// The Original Code is eCos - Embedded Cygnus Operating System, released
// September 30, 1998.
// 
// The Initial Developer of the Original Code is Cygnus.  Portions created
// by Cygnus are Copyright (C) 1998,1999 Cygnus Solutions.  All Rights Reserved.
// -------------------------------------------
//
//####COPYRIGHTEND####
//========================================================================
//#####DESCRIPTIONBEGIN####
//
// Author(s):   jlarmour
// Contributors:  jlarmour
// Date:        1998-02-13
// Purpose:     Configuration of the standard mathematical function library
// Description: Configuration header for mathematical function library
// Usage:       #include <pkgconf/libm.h>
//
//####DESCRIPTIONEND####
//
//========================================================================


//========================================================================
//
// A NOTE ON COMPATIBILITY MODES
//
// This math library is capable of being operated in several different
// compatibility modes. These options deal solely with how errors are
// handled.
//
// There are 4 compatibility modes: ANSI/POSIX 1003.1; IEEE-754; X/Open
// Portability Guide issue 3 (XPG3); and System V Interface Definition
// Edition 3.
//
// In IEEE mode, the matherr() function (see below) is never called, no
// warning messages are printed on the stderr output stream, and errno is
// never set.
//
// In ANSI/POSIX mode, errno is set correctly, but matherr() is never
// called and no warning messages are printed on the stderr output stream.
//
// In X/Open mode, errno is set correctly, matherr() is called, but no
// warning messages are printed on the stderr output stream.
//
// In SVID mode, functions which overflow return a value "HUGE" (defined in
// math.h), which is the maximum single precision floating point value
// (as opposed to HUGE_VAL which is meant to stand for infinity). errno is
// set correctly and matherr() is called. If matherr() returns 0, warning
// messages are printed on the stderr output stream for some errors.
//
// The mode can be compiled-in as IEEE-only, or any one of the above
// methods settable at run-time. See the configuration options below for
//  more.
//
//========================================================================
//
// MATHERR()
//
// As said, in X/Open or SVID modes, the user can supply a function
// matherr() of the form:
//
// int matherr( struct exception * );
//
// where:
// struct exception {
//     int type;
//     char *name;
//     double arg1, arg2, retval;
// };
//
// - type is the exception type and is one of:
// DOMAIN    - argument domain exception
// SING      - argument singularity
// OVERFLOW  - overflow range exception
// UNDERFLOW - underflow range exception
// TLOSS     - total loss of significance
// PLOSS     - partial loss of significance
//
// - name is a string containing the name of the function
// - arg1 and arg2 are the arguments passed to the function
// - retval is the default value that will be returned by the function, and
//   can be changed by matherr
// 
// matherr must have "C" linkage, not C++
//
// If matherr returns zero, or the user doesn't supply their own matherr,
// then the following _usually_ happens in SVID mode:
// 
// If type is:
//   DOMAIN    - 0.0 returned, errno=EDOM, and a message printed on stderr
//   SING      - HUGE of appropriate sign is returned, errno=EDOM, and a
//               message is printed on stderr
//   OVERFLOW  - HUGE of appropriate sign is returned, and errno=ERANGE
//   UNDERFLOW - 0.0 is returned and errno=ERANGE
//   TLOSS     - 0.0 is returned, errno=ERANGE, and a message is printed on
//               stderr
//   PLOSS     - The current implementation doesn't return this type
//
// X/Open mode is similar except that the message is not printed on stderr
// and HUGE_VAL is used in place of HUGE
//
//========================================================================
//
// THREAD-SAFETY AND RE-ENTRANCY
//
// With the appropriate configuration options set below, the math library
// is fully thread-safe if:
//
// - Depending on the compatibility mode, the setting of the errno variable
//   from the C library is thread-safe
//
// - Depending on the compatibility mode, sending error messages to the
//   stderr output stream using the C library fputs() function is
//   thread-safe
//
// - Depending on the compatibility mode, the user-supplied matherr()
//   function and anything it depends on are thread-safe
//
// In addition, with the exception of the gamma*() and lgamma*() functions,
// the math library is re-entrant (and thus safe to use from interrupt
// handlers) if the Math library is always in IEEE mode
//
//========================================================================
//
// Also note that this math library assumes the hardware (or software
// floating point emulation) supports IEEE-754 style arithmetic, 32-bit
// 2's complement integer arithmetic, doubles are in 64-bit
// IEEE-754 format.
//
//========================================================================


// INCLUDES

// Include system configuration file to work out whether the Math library
// is to be included at all
#include <pkgconf/system.h>

// We want to check if the kernel supports per-thread data
#ifdef CYGPKG_KERNEL
# include <pkgconf/kernel.h>
#endif

/*

    {{CFG_DATA
        cdl_package CYGPKG_LIBM {
            display      "Math library"
            description  "ISO standard floating point mathematical library
                          containing many useful functions for mathematical
                          calculations."
            type         boolean
            requires     CYGPKG_ERROR
            doc          ref/ecos-ref/the-iso-standard-c-and-math-libraries.html
        }
    }}CFG_DATA

*/

// TYPE DEFINITIONS

// Compatibility mode selector - required for default below

typedef enum {
    CYGNUM_LIBM_COMPAT_UNINIT= 0,  // Default state. DO NOT set it to this
    CYGNUM_LIBM_COMPAT_POSIX = 1,  // ANSI/POSIX 1003.1
    CYGNUM_LIBM_COMPAT_IEEE  = 2,  // IEEE-754
    CYGNUM_LIBM_COMPAT_XOPEN = 3,  // X/OPEN Portability guide issue 3
                                   // (XPG3)
    CYGNUM_LIBM_COMPAT_SVID  = 4   // System V Interface Definition 3rd
                                   // edition
} Cyg_libm_compat_t;


//========================================================================
//
// COMPATIBILITY-MODE RELATED CONFIGURATION OPTIONS

/*
    {{CFG_DATA

        cdl_component CYGPKG_LIBM_COMPATIBILITY {
            display      "Compatibility mode"
            description  "These options deal with behaviour related to
                          the various compatibility modes - POSIX, IEEE,
                          X/OPEN and SVID."
            doc          ref/ecos-ref/math-library-compatibility-modes.html
            type         dummy
            parent       CYGPKG_LIBM
        }

        cdl_option CYGSEM_LIBM_COMPAT_IEEE_ONLY {
            display      "IEEE-only"
            description  "The math library can be hard-coded to only
                          behave in one compatibility mode - IEEE. This
                          cannot be changed at run-time. IEEE mode is the
                          most minimal of the compatibility modes, and so