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-'\" t
-.\" Copyright (c) 2008, Linux Foundation, written by Michael Kerrisk
-.\" <mtk.manpages@gmail.com>
-.\"
-.\" SPDX-License-Identifier: Linux-man-pages-copyleft
-.\"
-.TH matherr 3 2024-02-26 "Linux man-pages 6.7"
-.SH NAME
-matherr \- SVID math library exception handling
-.SH LIBRARY
-Math library
-.RI ( libm ", " \-lm )
-.SH SYNOPSIS
-.nf
-.B #include <math.h>
-.P
-.BI "[[deprecated]] int matherr(struct exception *" exc );
-.P
-.B [[deprecated]] extern _LIB_VERSION_TYPE _LIB_VERSION;
-.fi
-.SH DESCRIPTION
-.IR Note :
-the mechanism described in this page is no longer supported by glibc.
-Before glibc 2.27, it had been marked as obsolete.
-Since glibc 2.27,
-.\" glibc commit 813378e9fe17e029caf627cab76fe23eb46815fa
-the mechanism has been removed altogether.
-New applications should use the techniques described in
-.BR math_error (7)
-and
-.BR fenv (3).
-This page documents the
-.BR matherr ()
-mechanism as an aid for maintaining and porting older applications.
-.P
-The System V Interface Definition (SVID) specifies that various
-math functions should invoke a function called
-.BR matherr ()
-if a math exception is detected.
-This function is called before the math function returns;
-after
-.BR matherr ()
-returns, the system then returns to the math function,
-which in turn returns to the caller.
-.P
-To employ
-.BR matherr (),
-the programmer must define the
-.B _SVID_SOURCE
-feature test macro
-(before including
-.I any
-header files),
-and assign the value
-.B _SVID_
-to the external variable
-.BR _LIB_VERSION .
-.P
-The system provides a default version of
-.BR matherr ().
-This version does nothing, and returns zero
-(see below for the significance of this).
-The default
-.BR matherr ()
-can be overridden by a programmer-defined
-version, which will be invoked when an exception occurs.
-The function is invoked with one argument, a pointer to an
-.I exception
-structure, defined as follows:
-.P
-.in +4n
-.EX
-struct exception {
- int type; /* Exception type */
- char *name; /* Name of function causing exception */
- double arg1; /* 1st argument to function */
- double arg2; /* 2nd argument to function */
- double retval; /* Function return value */
-}
-.EE
-.in
-.P
-The
-.I type
-field has one of the following values:
-.TP 12
-.B DOMAIN
-A domain error occurred (the function argument was outside the range
-for which the function is defined).
-The return value depends on the function;
-.I errno
-is set to
-.BR EDOM .
-.TP
-.B SING
-A pole error occurred (the function result is an infinity).
-The return value in most cases is
-.B HUGE
-(the largest single precision floating-point number),
-appropriately signed.
-In most cases,
-.I errno
-is set to
-.BR EDOM .
-.TP
-.B OVERFLOW
-An overflow occurred.
-In most cases, the value
-.B HUGE
-is returned, and
-.I errno
-is set to
-.BR ERANGE .
-.TP
-.B UNDERFLOW
-An underflow occurred.
-0.0 is returned, and
-.I errno
-is set to
-.BR ERANGE .
-.TP
-.B TLOSS
-Total loss of significance.
-0.0 is returned, and
-.I errno
-is set to
-.BR ERANGE .
-.TP
-.B PLOSS
-Partial loss of significance.
-This value is unused on glibc
-(and many other systems).
-.P
-The
-.I arg1
-and
-.I arg2
-fields are the arguments supplied to the function
-.RI ( arg2
-is undefined for functions that take only one argument).
-.P
-The
-.I retval
-field specifies the return value that the math
-function will return to its caller.
-The programmer-defined
-.BR matherr ()
-can modify this field to change the return value of the math function.
-.P
-If the
-.BR matherr ()
-function returns zero, then the system sets
-.I errno
-as described above, and may print an error message on standard error
-(see below).
-.P
-If the
-.BR matherr ()
-function returns a nonzero value, then the system does not set
-.IR errno ,
-and doesn't print an error message.
-.SS Math functions that employ matherr()
-The table below lists the functions and circumstances in which
-.BR matherr ()
-is called.
-The "Type" column indicates the value assigned to
-.I exc\->type
-when calling
-.BR matherr ().
-The "Result" column is the default return value assigned to
-.IR exc\->retval .
-.P
-The "Msg?" and "errno" columns describe the default behavior if
-.BR matherr ()
-returns zero.
-If the "Msg?" columns contains "y",
-then the system prints an error message on standard error.
-.P
-The table uses the following notations and abbreviations:
-.P
-.RS
-.TS
-l l.
-x first argument to function
-y second argument to function
-fin finite value for argument
-neg negative value for argument
-int integral value for argument
-o/f result overflowed
-u/f result underflowed
-|x| absolute value of x
-X_TLOSS is a constant defined in \fI<math.h>\fP
-.TE
-.RE
-.\" Details below from glibc 2.8's sysdeps/ieee754/k_standard.c
-.\" A subset of cases were test by experimental programs.
-.TS
-lB lB lB cB lB
-l l l c l.
-Function Type Result Msg? errno
-acos(|x|>1) DOMAIN HUGE y EDOM
-asin(|x|>1) DOMAIN HUGE y EDOM
-atan2(0,0) DOMAIN HUGE y EDOM
-acosh(x<1) DOMAIN NAN y EDOM \" retval is 0.0/0.0
-atanh(|x|>1) DOMAIN NAN y EDOM \" retval is 0.0/0.0
-atanh(|x|==1) SING (x>0.0)? y EDOM \" retval is x/0.0
-\ \ HUGE_VAL :
-\ \ \-HUGE_VAL
-cosh(fin) o/f OVERFLOW HUGE n ERANGE
-sinh(fin) o/f OVERFLOW (x>0.0) ? n ERANGE
-\ \ HUGE : \-HUGE
-sqrt(x<0) DOMAIN 0.0 y EDOM
-hypot(fin,fin) o/f OVERFLOW HUGE n ERANGE
-exp(fin) o/f OVERFLOW HUGE n ERANGE
-exp(fin) u/f UNDERFLOW 0.0 n ERANGE
-exp2(fin) o/f OVERFLOW HUGE n ERANGE
-exp2(fin) u/f UNDERFLOW 0.0 n ERANGE
-exp10(fin) o/f OVERFLOW HUGE n ERANGE
-exp10(fin) u/f UNDERFLOW 0.0 n ERANGE
-j0(|x|>X_TLOSS) TLOSS 0.0 y ERANGE
-j1(|x|>X_TLOSS) TLOSS 0.0 y ERANGE
-jn(|x|>X_TLOSS) TLOSS 0.0 y ERANGE
-y0(x>X_TLOSS) TLOSS 0.0 y ERANGE
-y1(x>X_TLOSS) TLOSS 0.0 y ERANGE
-yn(x>X_TLOSS) TLOSS 0.0 y ERANGE
-y0(0) DOMAIN \-HUGE y EDOM
-y0(x<0) DOMAIN \-HUGE y EDOM
-y1(0) DOMAIN \-HUGE y EDOM
-y1(x<0) DOMAIN \-HUGE y EDOM
-yn(n,0) DOMAIN \-HUGE y EDOM
-yn(x<0) DOMAIN \-HUGE y EDOM
-lgamma(fin) o/f OVERFLOW HUGE n ERANGE
-lgamma(\-int) or SING HUGE y EDOM
-\ \ lgamma(0)
-tgamma(fin) o/f OVERFLOW HUGE_VAL n ERANGE
-tgamma(\-int) SING NAN y EDOM
-tgamma(0) SING copysign( y ERANGE
-\ \ HUGE_VAL,x)
-log(0) SING \-HUGE y EDOM
-log(x<0) DOMAIN \-HUGE y EDOM
-log2(0) SING \-HUGE n EDOM \" different from log()
-log2(x<0) DOMAIN \-HUGE n EDOM \" different from log()
-log10(0) SING \-HUGE y EDOM
-log10(x<0) DOMAIN \-HUGE y EDOM
-pow(0.0,0.0) DOMAIN 0.0 y EDOM
-pow(x,y) o/f OVERFLOW HUGE n ERANGE
-pow(x,y) u/f UNDERFLOW 0.0 n ERANGE
-pow(NaN,0.0) DOMAIN x n EDOM
-0**neg DOMAIN 0.0 y EDOM \" +0 and -0
-neg**non-int DOMAIN 0.0 y EDOM
-scalb() o/f OVERFLOW (x>0.0) ? n ERANGE
-\ \ HUGE_VAL :
-\ \ \-HUGE_VAL
-scalb() u/f UNDERFLOW copysign( n ERANGE
-\ \ \ \ 0.0,x)
-fmod(x,0) DOMAIN x y EDOM
-remainder(x,0) DOMAIN NAN y EDOM \" retval is 0.0/0.0
-.TE
-.SH ATTRIBUTES
-For an explanation of the terms used in this section, see
-.BR attributes (7).
-.TS
-allbox;
-lbx lb lb
-l l l.
-Interface Attribute Value
-T{
-.na
-.nh
-.BR matherr ()
-T} Thread safety MT-Safe
-.TE
-.SH EXAMPLES
-The example program demonstrates the use of
-.BR matherr ()
-when calling
-.BR log (3).
-The program takes up to three command-line arguments.
-The first argument is the floating-point number to be given to
-.BR log (3).
-If the optional second argument is provided, then
-.B _LIB_VERSION
-is set to
-.B _SVID_
-so that
-.BR matherr ()
-is called, and the integer supplied in the
-command-line argument is used as the return value from
-.BR matherr ().
-If the optional third command-line argument is supplied,
-then it specifies an alternative return value that
-.BR matherr ()
-should assign as the return value of the math function.
-.P
-The following example run, where
-.BR log (3)
-is given an argument of 0.0, does not use
-.BR matherr ():
-.P
-.in +4n
-.EX
-.RB "$" " ./a.out 0.0"
-errno: Numerical result out of range
-x=\-inf
-.EE
-.in
-.P
-In the following run,
-.BR matherr ()
-is called, and returns 0:
-.P
-.in +4n
-.EX
-.RB "$" " ./a.out 0.0 0"
-matherr SING exception in log() function
- args: 0.000000, 0.000000
- retval: \-340282346638528859811704183484516925440.000000
-log: SING error
-errno: Numerical argument out of domain
-x=\-340282346638528859811704183484516925440.000000
-.EE
-.in
-.P
-The message "log: SING error" was printed by the C library.
-.P
-In the following run,
-.BR matherr ()
-is called, and returns a nonzero value:
-.P
-.in +4n
-.EX
-.RB "$" " ./a.out 0.0 1"
-matherr SING exception in log() function
- args: 0.000000, 0.000000
- retval: \-340282346638528859811704183484516925440.000000
-x=\-340282346638528859811704183484516925440.000000
-.EE
-.in
-.P
-In this case, the C library did not print a message, and
-.I errno
-was not set.
-.P
-In the following run,
-.BR matherr ()
-is called, changes the return value of the math function,
-and returns a nonzero value:
-.P
-.in +4n
-.EX
-.RB "$" " ./a.out 0.0 1 12345.0"
-matherr SING exception in log() function
- args: 0.000000, 0.000000
- retval: \-340282346638528859811704183484516925440.000000
-x=12345.000000
-.EE
-.in
-.SS Program source
-\&
-.\" SRC BEGIN (matherr.c)
-.EX
-#define _SVID_SOURCE
-#include <errno.h>
-#include <math.h>
-#include <stdio.h>
-#include <stdlib.h>
-\&
-static int matherr_ret = 0; /* Value that matherr()
- should return */
-static int change_retval = 0; /* Should matherr() change
- function\[aq]s return value? */
-static double new_retval; /* New function return value */
-\&
-int
-matherr(struct exception *exc)
-{
- fprintf(stderr, "matherr %s exception in %s() function\en",
- (exc\->type == DOMAIN) ? "DOMAIN" :
- (exc\->type == OVERFLOW) ? "OVERFLOW" :
- (exc\->type == UNDERFLOW) ? "UNDERFLOW" :
- (exc\->type == SING) ? "SING" :
- (exc\->type == TLOSS) ? "TLOSS" :
- (exc\->type == PLOSS) ? "PLOSS" : "???",
- exc\->name);
- fprintf(stderr, " args: %f, %f\en",
- exc\->arg1, exc\->arg2);
- fprintf(stderr, " retval: %f\en", exc\->retval);
-\&
- if (change_retval)
- exc\->retval = new_retval;
-\&
- return matherr_ret;
-}
-\&
-int
-main(int argc, char *argv[])
-{
- double x;
-\&
- if (argc < 2) {
- fprintf(stderr, "Usage: %s <argval>"
- " [<matherr\-ret> [<new\-func\-retval>]]\en", argv[0]);
- exit(EXIT_FAILURE);
- }
-\&
- if (argc > 2) {
- _LIB_VERSION = _SVID_;
- matherr_ret = atoi(argv[2]);
- }
-\&
- if (argc > 3) {
- change_retval = 1;
- new_retval = atof(argv[3]);
- }
-\&
- x = log(atof(argv[1]));
- if (errno != 0)
- perror("errno");
-\&
- printf("x=%f\en", x);
- exit(EXIT_SUCCESS);
-}
-.EE
-.\" SRC END
-.SH SEE ALSO
-.BR fenv (3),
-.BR math_error (7),
-.BR standards (7)
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-08 10:57:59 +0000