MATHERR(3M)MATHERR(3M)NAMEmatherr - error-handling function
SYNOPSIS
#include <math.h>
int matherr (struct exception *x);
DESCRIPTIONmatherr is invoked by the following functions in libmx.a when errors are
detected:
acos acosf acosh asin asinf asinh atan atanf atan2 atan2f atanh cbrt cos
cosf cosh coshf drem erf erfc
exp expf expm1 expm1f fmod fmodf gamma hypot hypotf j0 j1 jn lgamma log
logf log10 log10f log1p log1pf
pow powf sin sinf sinh sinhf sqrt sqrtf tan tanf tanh tanhf y0 y1 yn
Note that to use matherr, libmx.a needs to be linked with the program.
Users may define their own routines 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 math.h):
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 elements 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.
NaN argument(s) to any of the above functions generates a call to matherr
with a domain error.
Page 1
MATHERR(3M)MATHERR(3M)
If the user's matherr function returns non-zero, no error message will be
printed by the calling function, and errno will not be set.
If matherr is not supplied by the user, the default error-handling
procedures, described by the table below, will be invoked upon error. In
every case, errno is set to EDOM or ERANGE and the program continues.
Page 2
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
______________________________________________________________________________
EXP, EXPF: - - M, H M, 0 - -
______________________________________________________________________________
EXPM1, EXPM1F: - - M, H M, 0 - -
______________________________________________________________________________
LOG, LOGF:
LOG10, LOG10F:
(arg < 0) M, N - - - - -
(arg = 0) M, -H - - - - -
______________________________________________________________________________
LOG1P, LOG1PF:
(arg < -1) M, N - - - - -
(arg = -1) M, -H - - - - -
______________________________________________________________________________
POW, POWF: - - _H 0 - -
neg ** non-int M, 0 - - - - -
0 ** non-pos M, H - - - - -
______________________________________________________________________________
SQRT, SQRTF: M, N - - - - -
______________________________________________________________________________
DREM, FMOD, FMODF:
(arg1 = +/-inf M, N - - - - -
or arg2 = 0)
______________________________________________________________________________
GAMMA, LGAMMA: - M, H M, H - - -
______________________________________________________________________________
J0, J1, JN: - - - - M, 0 -
______________________________________________________________________________
Y0, Y1, YN:
(arg = 0) - - M, -H - - -
(arg < 0) M, N - - - - -
(arg >= 2**49) - - - - M, 0 -
______________________________________________________________________________
SINH, SINHF: - - _H - - -
______________________________________________________________________________
COSH, COSHF: - - H - - -
______________________________________________________________________________
HYPOT, HYPOTF: - - M, H - - -
______________________________________________________________________________
ASIN, ASINF:
ACOS, ACOSF: M, N - - - - -
____________________________________________________________________________________________________________________________________________________________
|
|
|
|
|
|
|
|
Page 3
MATHERR(3M)MATHERR(3M)
SIN, COS, TAN:
(arg >= 2**50) M, N - - - - -
(arg = +/-inf) - - - - M, 0 -
______________________________________________________________________________
SINF, COSF, TANF:
(arg >= 2**22) M, N - - - - -
(arg = +/-inf) - - - - M, 0 -
______________________________________________________________________________
ATAN2, ATAN2F: M, 0 - - - - -
______________________________________________________________________________
ACOSH: M, N - - - - -
______________________________________________________________________________
ATANH:
(|arg| > 1) M, N - - - - -
______________________________________________________________________________
|
|
|
|
|
|
|
|
______________________________________________________________________________
Abbreviations
M Message is printed
H HUGE is returned
-H-HUGE is returned
_H HUGE or -HUGE is returned.
0 0 is returned.
X arg1 is returned.
N NaN is returned.
______________________________________________________________________________
|
|
Page 4
MATHERR(3M)MATHERR(3M)EXAMPLE
/*
** Example showing the use of libmx.a's matherr() to handle math errors.
**
** % cc -xansi my_matherr.c -lmx
** % a.out
** overflow range error in logf
** logf(0.0) is -inf.
**
** expf failed: Argument out of domain
** Abort (core dumped)
*/
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
main()
{
float ff;
ff = logf(0.0f); /* matherr() leaves error reporting to libmx.a */
printf("logf(0.0f) is %f.\n\n",ff);
fflush(stdout);
ff = 0.0f;
ff = 0.0f/ff;
ff = expf(ff); /* matherr() customized to force a core dump */
}
int matherr( register struct exception *x )
{
char *sterr;
switch (x->type) {
case DOMAIN:
/* if it's a NaN, abort */
if ( isnan(x->arg1) )
{
sterr = strerror(EDOM);
fprintf(stderr, "%s failed: %s\n", x->name, sterr);
abort();
}
else if ( !strcmp(x->name, "sin") )
{
x->retval = 0.0; /* return 0.0 */
fprintf(stderr, "domain error in sin\n");
Page 5
MATHERR(3M)MATHERR(3M)
return (1); /* suppress libmx.a error message and setting of errno */
}
else
return (0); /* libmx.a prints error message and sets errno */
break;
default:
return (0); /* libmx.a prints error message and sets errno */
}
}
NOTES
Errors detected by functions in libm.a can be detected by examining the
return value and/or the global variable errno. libmx.a is provided as an
alternative error handling scheme for users who want to identify specific
kinds of errors determined by libm functions without extensive
modification of their source code.
No extra overhead is incurred by programs using libmx.a if no error
conditions are encountered in the libmx routines.
Page 6
