MATHERR(3) BSD Programmer's Manual MATHERR(3)NAMEmatherr - report errors in math library functions
SYNOPSIS
#include <math.h>
/* Modes: */
typedef enum {
_IEEE_ = -1,
_SVID_,
_XOPEN_,
_POSIX_
} _LIB_VERSION_TYPE;
extern _LIB_VERSION_TYPE _LIB_VERSION;
struct exception {
int type;
char *name;
double arg1;
double arg2;
double retval;
};
/* Types: */
#define DOMAIN 1
#define SING 2
#define OVERFLOW 3
#define UNDERFLOW 4
#define TLOSS 5
#define PLOSS 6
int
matherr(struct exception *exc);
DESCRIPTION
The matherr() function is a function that math library functions (see
math(3)) call when they detect an error. Normally, you provide your own
version of matherr() if you need to process math library errors special-
ly. This makes matherr() different from most library functions, which
are not designed to be replaced by users.
The matherr() function is only called from the math library in a very
specific set of conditions:
o You link your program to the generic math library, -lmstd. Hardware-
specific math libraries under BSD/OS support only IEEE 754 semantics.
o You assign _XOPEN_ or _SVID_ to the global variable _LIB_VERSION be-
fore calling any math library function that may in turn need to call
matherr(). The default mode is _IEEE_, in which errors are reported
using exceptions (see fpgetsticky(3)).
o You call a math library function that reports an error using
matherr(), as documented in that function's manual page.
o Your code presents an exceptional condition for that math library
function, as documented in the manual page.
If the return value of matherr() is nonzero, the error is ignored and
errno is unaltered. If the return value is 0, errno is set to EDOM or
ERANGE to indicate the error appropriately. If the return value is 0 and
_LIB_VERSION is set to _SVID_, a message describing the error may be
printed to stderr.
Library functions call matherr() with a pointer to an exception struc-
ture. The members of this structure have the following meanings:
type The type of the error:
DOMAIN The value of an argument to the function is not in
the domain on which the function is defined.
SING The value of an argument to the function lies in a
singularity; the result of the function at this
point is infinite.
OVERFLOW The magnitude of the result of the function is
larger than the largest magnitude that the floating
point format can represent, even though the argu-
ments were finite and in the function's domain.
UNDERFLOW The magnitude of the result of the function is
smaller than the smallest magnitude that the float-
ing point format can represent, even though the ar-
guments were finite and in the function's domain.
TLOSS The result of the function has a total loss of sig-
nificance.
PLOSS The result of the function has a partial loss of
significance.
name A string that represents the nul-terminated name of the func-
tion.
arg1 The first argument to the function.
arg2 The second argument to the function (if more than one).
retval The result of the function. If matherr() changes this value,
the library function will appear to return the new value to the
caller.
The library provides a default version of matherr(). The default
matherr() always returns 0. If the first argument to the function is an
IEEE 754 NaN, it will report an invalid operation exception (see
fpgetsticky(3)).
SEE ALSOmath(3)BUGS
You can't replace a function in a static shared library, so programs that
are compiled with shlicc(1) may not use matherr().
It's not clear what version of the SVID, if any, this implementation
might be compatible with.
BSDI BSD/OS March 4, 1998 2
