matherr
—modifiable math error handlerSynopsis
#include <math.h> int matherr(struct exception *e);
Description
matherr
is called whenever a math library function generates an error.
You can replace matherr
by your own subroutine to customize
error treatment. The customized matherr
must return 0 if
it fails to resolve the error, and non-zero if the error is resolved.
When matherr
returns a nonzero value, no error message is printed
and the value of errno
is not modified. You can accomplish either
or both of these things in your own matherr
using the information
passed in the structure *e
.
This is the exception
structure (defined in ‘math.h
’):
struct exception { int type; char *name; double arg1, arg2, retval; int err; };
The members of the exception structure have the following meanings:
type
The type of mathematical error that occured; macros encoding error
types are also defined in ‘math.h
’.
name
a pointer to a null-terminated string holding the name of the math library function where the error occurred.
arg1, arg2
The arguments which caused the error.
retval
The error return value (what the calling function will return).
err
If set to be non-zero, this is the new value assigned to errno
.
The error types defined in ‘math.h
’ represent possible mathematical
errors as follows:
DOMAIN
An argument was not in the domain of the function; e.g. log(-1.0)
.
SING
The requested calculation would result in a singularity; e.g. pow(0.0,-2.0)
OVERFLOW
A calculation would produce a result too large to represent; e.g.
exp(1000.0)
.
UNDERFLOW
A calculation would produce a result too small to represent; e.g.
exp(-1000.0)
.
TLOSS
Total loss of precision. The result would have no significant digits;
e.g. sin(10e70)
.
PLOSS
Partial loss of precision.
Returns
The library definition for matherr
returns 0
in all cases.
You can change the calling function’s result from a customized matherr
by modifying e->retval
, which propagates backs to the caller.
If matherr
returns 0
(indicating that it was not able to resolve
the error) the caller sets errno
to an appropriate value, and prints
an error message.
Portability
matherr
is not ANSI C.