matherr(3M) DG/UX 5.4.2 matherr(3M)
NAME
matherr - error-handling function
SYNOPSIS
cc [flag ...] file ... -lm [library ...]
#include <math.h>
int matherr (struct exception *x);
DESCRIPTION
matherr is invoked by functions in the math libraries when errors are
detected. Note that matherr is not invoked when the -Xc compilation
option is used. Users may define their own procedures for handling
errors, by including a function named matherr in their programs.
matherr must be of the form described above. When an error occurs, a
pointer to the exception structure x 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 element type is an integer describing the type of error that has
occurred, from the following list of constants (defined in the header
file):
DOMAIN argument domain error
SING argument singularity
OVERFLOW overflow range error
UNDERFLOW underflow range error
TLOSS total loss of significance
PLOSS partial loss of significance
The element name points to a string containing the name of the
function that incurred the error. The variables arg1 and arg2 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 error message
will be printed, and errno will not be set.
If matherr is not supplied by the user, the default error-handling
procedures, described with the math functions involved, will be
invoked upon error. These procedures are also summarized in the
table below. In every case, errno is set to EDOM or ERANGE and the
program continues.
Licensed material--property of copyright holder(s) 1
matherr(3M) DG/UX 5.4.2 matherr(3M)
+------------------------------------------------------------------------+
| Default Error Handling Procedures |
+---------------------+--------------------------------------------------+
| | Types of Errors |
+---------------------+-------+-----+----------+----------+------+-------+
| type |DOMAIN | SING|OVERFLOW UNDERFLOW |TLOSS |PLOSS |
+---------------------+-------+-----+----------+----------+------+-------+
| errno | EDOM | EDOM| ERANGE | ERANGE |ERANGE|ERANGE |
+---------------------+-------+-----+----------+----------+------+-------+
|BESSEL: | - | - | - | - | M, 0 | - |
|y0, y1, yn (arg < 0) |M, -H | - | - | - | - | - |
+---------------------+-------+-----+----------+----------+------+-------+
|EXP, EXPF: | - | - | H | 0 | - | - |
+---------------------+-------+-----+----------+----------+------+-------+
|LOG, LOG10: | | | | | | |
|LOGF, LOG10F: | | | | | | |
| (arg < 0) | M, -H | - | - | - | - | - |
| (arg = 0) | M, -H | - | - | - | - | - |
+---------------------+-------+-----+----------+----------+------+-------+
|POW, POWF: | - | - | ±H | 0 | - | - |
|neg ** non-int | M, 0 | - | - | - | - | - |
| 0 ** non-pos | M, 0 | - | - | - | - | - |
+---------------------+-------+-----+----------+----------+------+-------+
|SQRT, SQRTF: | M, 0 | - | - | - | - | - |
+---------------------+-------+-----+----------+----------+------+-------+
|FMOD, FMODF: | | | | | | |
| (arg2 = 0) | M, X | - | - | - | - | - |
+---------------------+-------+-----+----------+----------+------+-------+
|REMAINDER: | | | | | | |
| (arg2 = 0) | M, N | - | - | - | - | - |
+---------------------+-------+-----+----------+----------+------+-------+
|GAMMA, LGAMMA: | - | M, H| H | - | - | - |
+---------------------+-------+-----+----------+----------+------+-------+
|HYPOT: | - | - | H | - | - | - |
+---------------------+-------+-----+----------+----------+------+-------+
|SINH, SINHF: | - | - | ±H | - | - | - |
+---------------------+-------+-----+----------+----------+------+-------+
|COSH, COSHF: | - | - | H | - | - | - |
+---------------------+-------+-----+----------+----------+------+-------+
|ASIN, ACOS, ATAN2: | | | | | | |
|ASINF, ACOSF, ATAN2F:| M, 0 | - | - | - | - | - |
+---------------------+-------+-----+----------+----------+------+-------+
|ACOSH: | M, N | - | - | - | - | - |
+---------------------+-------+-----+----------+----------+------+-------+
|ATANH: | | | | | | |
| (|arg| > 1) | M, N | - | - | - | - | - |
| (|arg| = 1) | - |M, N | - | - | - | - |
+---------------------+-------+-----+----------+----------+------+-------+
Licensed material--property of copyright holder(s) 2
matherr(3M) DG/UX 5.4.2 matherr(3M)
+----------------------------------------------------------------+
| Abbreviations |
| M Message is printed (not with the -Xa or -Xc options). |
| H HUGE is returned (HUGEVAL with the -Xa or -Xc options). |
|-H -HUGE is returned (-HUGEVAL with the -Xa or -Xc options). |
|±H HUGE or -HUGE is returned. |
| (HUGEVAL or -HUGEVAL with the -Xa or -Xc options). |
| 0 0 is returned. |
| X arg1 is returned. |
| N NaN is returned. |
+----------------------------------------------------------------+
EXAMPLE
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int
matherr(register struct exception *x);
{
switch (x->type) {
case DOMAIN:
/* change sqrt to return sqrt(-arg1), not 0 */
if (!strcmp(x->name, "sqrt")) {
x->retval = sqrt(-x->arg1);
return (0); /* print message and set errno */
}
case SING:
/* all other domain or sing errors, print message */
/* and abort */
fprintf(stderr, "domain error in %s\n", x->name);
abort( );
case PLOSS:
/* print detailed error message */
fprintf(stderr, "loss of significance in %s(%g)=%g\n",
x->name, x->arg1, x->retval);
return (1); /* take no other action */
}
return (0); /* all other errors, execute default procedure */
}
SEE ALSO
erf(3M).
NOTES
Error handling in -Xa and -Xt modes [see cc(1)] is described more
completely on individual math library pages.
Licensed material--property of copyright holder(s) 3