matherr(3M) 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 -kansi com-
pilation option is used. Users may define their own procedures for
handling errors, by including a function named matherr() in their pro-
grams. 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 a number of type int 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 func-
tion 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 matherr()
sets it to a different value.
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matherr(3M) matherr(3M)
If the 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.
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matherr(3M) 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| - | - | - | - |
|_____________________|_______|_____|_________|__________|_______|_______|
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matherr(3M) matherr(3M)
Abbreviations
M Message is printed (not in the ANSI mode).
H HUGE is returned (HUGEVAL in the ANSI mode).
-H -HUGE is returned (-HUGEVAL in the ANSI mode).
+H HUGE or -HUGE is returned (HUGEVAL or -HUGEVAL in the ANSI
mode).
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
math(5).
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