MATHERR(3M) Mathematical Library Functions MATHERR(3M)

NAME

matherr - math library exception-handling function

SYNOPSIS

#include <math.h>

int matherr(struct exception *exc);

DESCRIPTION

The System V Interface Definition, Third Edition (SVID3) specifies
that certain libm functions call matherr() when exceptions are
detected. Users may define their own mechanisms for handling
exceptions, by including a function named matherr() in their
programs. The matherr() function is of the form described above. When
an exception occurs, a pointer to the exception structure exc will be
passed to the user-supplied matherr() function. This structure,
which is defined in the <math.h> header file, is as follows:

struct exception {
int type;
char *name;
double arg1, arg2, retval;
};


The type member is an integer describing the type of exception that
has occurred, from the following list of constants (defined in the
header file):

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


Both TLOSS and PLOSS reflect limitations of particular algorithms for
trigonometric functions that suffer abrupt declines in accuracy at
definite boundaries. Since the implementation does not suffer such
abrupt declines, PLOSS is never signaled. TLOSS is signaled for
Bessel functions only to satisfy SVID3 requirements.


The name member points to a string containing the name of the
function that incurred the exception. The arg1 and arg2 members are
the arguments with which the function was invoked. retval is set to
the default value that will be returned by the function unless the
user's matherr() sets it to a different value.


If the user's matherr() function returns non-zero, no exception
message will be printed and errno is not set.

SVID3 STANDARD CONFORMANCE
When an application is built as a SVID3 conforming application (see
standards(7)), if matherr() is not supplied by the user, the default
matherr exception-handling mechanisms, summarized in the table below,
are invoked upon exception:

DOMAIN
0.0 is usually returned, errno is set to EDOM and a
message is usually printed on standard error.


SING
The largest finite single-precision number, HUGE of
appropriate sign, is returned, errno is set to EDOM, and
a message is printed on standard error.


OVERFLOW
The largest finite single-precision number, HUGE of
appropriate sign, is usually returned and errno is set
to ERANGE.


UNDERFLOW
0.0 is returned and errno is set to ERANGE.


TLOSS
0.0 is returned, errno is set to ERANGE, and a message
is printed on standard error.


In general, errno is not a reliable error indicator because it can be
unexpectedly set by a function in a handler for an asynchronous
signal.

SVID3 ERROR HANDLING PROCEDURES (compile with cc \-Xt)


+-------------------------------+-------------------+------------------+-------------+--------------+---------+
| <math.h> type | DOMAIN | SING | OVERFLOW | UNDERFLOW | TLOSS |
+-------------------------------+-------------------+------------------+-------------+--------------+---------+
|errno | EDOM | EDOM | ERANGE | ERANGE | ERANGE |
+-------------------------------+-------------------+------------------+-------------+--------------+---------+
|IEEE Exception | Invalid Operation | Division by Zero | Overflow | Underflow | - |
+-------------------------------+-------------------+------------------+-------------+--------------+---------+
|fp_exception_type | fp_invalid | fp_division | fp_overflow | fp_underflow | - |
+-------------------------------+-------------------+------------------+-------------+--------------+---------+
|ACOS, ASIN(|x| > 1): | Md, 0.0 | - | - | - | - |
+-------------------------------+-------------------+------------------+-------------+--------------+---------+
|ACOSH(x < 1), ATANH(|x| > 1): | NaN | - | - | - | - |
+-------------------------------+-------------------+------------------+-------------+--------------+---------+
|ATAN2(0,0): | Md, 0.0 | - | - | - | - |
+-------------------------------+-------------------+------------------+-------------+--------------+---------+
|COSH, SINH: | - | - | +-HUGE | - | - |
+-------------------------------+-------------------+------------------+-------------+--------------+---------+
|EXP: | - | - | +HUGE | 0.0 | - |
+-------------------------------+-------------------+------------------+-------------+--------------+---------+
|FMOD(x,0): | x | - | - | - | - |
+-------------------------------+-------------------+------------------+-------------+--------------+---------+
|HYPOT: | - | - | +HUGE | - | - |
+-------------------------------+-------------------+------------------+-------------+--------------+---------+
|J0, J1, JN(|x| > X_TLOSS): | - | - | - | - | Mt, 0.0 |
+-------------------------------+-------------------+------------------+-------------+--------------+---------+
|LGAMMA: | | | | | |
| usual cases | - | - | +HUGE | - | - |
| (x = 0 or -integer) | - | Ms, +HUGE | - | - | - |
+-------------------------------+-------------------+------------------+-------------+--------------+---------+
|LOG, LOG10: | | | | | |
| (x < 0) | Md, -HUGE | - | - | - | - |
| (x = 0) | - | Ms, -HUGE | - | - | - |
+-------------------------------+-------------------+------------------+-------------+--------------+---------+
|POW: | | | | | |
| usual cases | - | - | +-HUGE | +-0.0 | - |
| (x < 0) ** (y not an integer) | Md, 0.0 | - | - | - | - |
| 0 ** 0 | Md, 0.0 | - | - | - | - |
| 0 ** (y < 0) | Md, 0.0 | - | - | - | |
+-------------------------------+-------------------+------------------+-------------+--------------+---------+
|REMAINDER(x,0): | NaN | - | - | - | - |
+-------------------------------+-------------------+------------------+-------------+--------------+---------+
|SCALB: | - | - | +-HUGE_VAL | +-0.0 | - |
+-------------------------------+-------------------+------------------+-------------+--------------+---------+
|SQRT(x < 0): | Md, 0.0 | - | - | - | - |
+-------------------------------+-------------------+------------------+-------------+--------------+---------+
|Y0, Y1, YN: | | | | | |
| (x < 0) | Md, -HUGE | - | - | - | - |
| (x = 0) | - | Md, -HUGE | - | - | - |
| (x > X_TLOSS) | - | - | - | - | Mt, 0.0 |
+-------------------------------+-------------------+------------------+-------------+--------------+---------+

Abbreviations

Md
Message is printed (DOMAIN error).


Ms
Message is printed (SING error).


Mt
Message is printed (TLOSS error).


NaN
IEEE NaN result and invalid operation exception.


HUGE
Maximum finite single-precision floating-point number.


HUGE_VAL
IEEE <infinity> result and division-by-zero exception.


X_TLOSS
The value X_TLOSS is defined in <values.h>.


The interaction of IEEE arithmetic and matherr() is not defined when
executing under IEEE rounding modes other than the default round to
nearest: matherr() is not always called on overflow or underflow and
can return results that differ from those in this table.

X/OPEN COMMON APPLICATION ENVIRONMENT (CAE) SPECIFICATIONS CONFORMANCE
The X/Open System Interfaces and Headers (XSH) Issue 3 and later
revisions of that specification no longer sanctions the use of the
matherr interface. The following table summarizes the values
returned in the exceptional cases. In general, XSH dictates that as
long as one of the input argument(s) is a NaN, NaN is returned. In
particular, pow(NaN,0) = NaN.

CAE SPECIFICATION ERROR HANDLING PROCEDURES (compile with cc -Xa)


+-------------------------------+-------------+-------------+--------------+------------+---------+
| <math.h> type | DOMAIN | SING | OVERFLOW | UNDERFLOW | TLOSS |
+-------------------------------+-------------+-------------+--------------+------------+---------+
|errno | EDOM | EDOM | ERANGE | ERANGE | ERANGE |
+-------------------------------+-------------+-------------+--------------+------------+---------+
|ACOS, ASIN(|x| > 1): | 0.0 | - | - | - | - |
+-------------------------------+-------------+-------------+--------------+------------+---------+
|ATAN2(0,0): | 0.0 | - | - | - | - |
+-------------------------------+-------------+-------------+--------------+------------+---------+
|COSH, SINH: | - | - | {+-HUGE_VAL} | - | - |
+-------------------------------+-------------+-------------+--------------+------------+---------+
|EXP: | - | - | {+HUGE_VAL} | {0.0} | - |
+-------------------------------+-------------+-------------+--------------+------------+---------+
|FMOD(x,0): | {NaN} | - | - | - | - |
+-------------------------------+-------------+-------------+--------------+------------+---------+
|HYPOT: | - | - | {+HUGE_VAL} | - | - |
+-------------------------------+-------------+-------------+--------------+------------+---------+
|J0, J1, JN(|x| > X_TLOSS): | - | - | - | - | {0.0} |
+-------------------------------+-------------+-------------+--------------+------------+---------+
|LGAMMA: | | | | | |
| usual cases | - | - | {+HUGE_VAL} | - | - |
| (x = 0 or -integer) | - | +HUGE_VAL | - | - | - |
+-------------------------------+-------------+-------------+--------------+------------+---------+
|LOG, LOG10: | | | | | |
| (x < 0) | -HUGE_VAL | - | - | - | - |
| (x = 0) | - | -HUGE_VAL | - | - | - |
+-------------------------------+-------------+-------------+--------------+------------+---------+
|POW: | | | | | |
| usual cases | - | - | +-HUGE_VAL | +-0.0 | - |
| (x < 0) ** (y not an integer) | 0.0 | - | - | - | - |
| 0 ** 0 | {1.0} | - | - | - | - |
| 0 ** (y < 0) | {-HUGE_VAL} | - | - | - | - |
+-------------------------------+-------------+-------------+--------------+------------+---------+
|SQRT(x < 0): | 0.0 | - | - | - | - |
+-------------------------------+-------------+-------------+--------------+------------+---------+
|Y0, Y1, YN: | | | | | |
| (x < 0) | {-HUGE_VAL} | - | - | - | - |
| (x = 0) | - | {-HUGE_VAL} | - | - | - |
| (x > X_TLOSS) | - | - | - | - | 0.0 |
+-------------------------------+-------------+-------------+--------------+------------+---------+

Abbreviations

{...}
errno is not to be relied upon in all braced cases.


NaN
IEEE NaN result and invalid operation exception.


HUGE_VAL
IEEE <infinity> result and division-by-zero exception.


X_TLOSS
The value X_TLOSS is defined in <values.h>.


ANSI/ISO-C STANDARD CONFORMANCE
The ANSI/ISO-C standard covers a small subset of the CAE
specification.


The following table summarizes the values returned in the exceptional
cases.

ANSI/ISO-C ERROR HANDLING PROCEDURES (compile with cc -Xc)


+-------------------------------+-------------+-------------+-------------+-------------+
| <math.h> type | DOMAIN | SING | OVERFLOW | UNDERFLOW |
+-------------------------------+-------------+-------------+-------------+-------------+
|errno | EDOM | EDOM | ERANGE | ERANGE |
+-------------------------------+-------------+-------------+-------------+-------------+
|ACOS, ASIN(|x| > 1): | 0.0 | - | - | - |
+-------------------------------+-------------+-------------+-------------+-------------+
|ATAN2(0,0): | 0.0 | - | - | - |
+-------------------------------+-------------+-------------+-------------+-------------+
|EXP: | - | - | +HUGE_VAL | 0.0 |
+-------------------------------+-------------+-------------+-------------+-------------+
|FMOD(x,0): | NaN | - | - | - |
+-------------------------------+-------------+-------------+-------------+-------------+
|LOG, LOG10: | | | | |
| (x < 0) | -HUGE_VAL | - | - | - |
| (x = 0) | - | -HUGE_VAL | - | - |
+-------------------------------+-------------+-------------+-------------+-------------+
|POW: | | | | |
| usual cases | - | - | +-HUGE_VAL | +-0.0 |
| (x < 0) ** (y not an integer) | 0.0 | - | - | - |
| 0 ** (y < 0) | -HUGE_VAL | - | - | - |
+-------------------------------+-------------+-------------+-------------+-------------+
|SQRT(x < 0): | 0.0 | - | - | - |
+-------------------------------+-------------+-------------+-------------+-------------+

ABBREVIATIONS

NaN
IEEE NaN result and invalid operation exception.


HUGE_VAL
IEEE <infinity> result and division-by-zero.

EXAMPLES

Example 1: Example of matherr() function

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

int
matherr(struct exception *x) {
switch (x->type) {
case DOMAIN:
/* change sqrt to return sqrt(-arg1), not NaN */
if (!strcmp(x->name, "sqrt")) {
x->retval = sqrt(-x->arg1);
return (0); /* print message and set errno */
} /* FALLTHRU */
case SING:
/* all other domain or sing exceptions, print message and */
/* abort */
fprintf(stderr, "domain exception in %s\n", x->name);
abort( );
break;
}
return (0); /* all other exceptions, execute default procedure */
}

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:


+----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+----------------------------+-----------------------------+
|MT-Level | MT-Safe |
+----------------------------+-----------------------------+

SEE ALSO

attributes(7), standards(7)

SunOS 5.11 September 23, 1997 MATHERR(3M)