FEUPDATEENV(3M) Mathematical Library Functions FEUPDATEENV(3M)
NAME
feupdateenv - update floating-point environment
SYNOPSIS
c99 [
flag... ]
file...
-lm [
library... ]
#include <fenv.h>
int feupdateenv(
const fenv_t *envp);
DESCRIPTION
The
feupdateenv() function attempts to save the currently raised
floating-point exceptions in its automatic storage, attempts to
install the floating-point environment represented by the object
pointed to by
envp, and then attempts to raise the saved floating-
point exceptions. The
envp argument points to an object set by a call
to
fegetenv(3M) or
feholdexcept(3M), or equals a floating-point
environment macro.
RETURN VALUES
The
feupdateenv() function returns 0 if and only if all the required
actions were successfully carried out.
ERRORS
No errors are defined.
EXAMPLES
The following example demonstrates sample code to hide spurious
underflow floating-point exceptions:
Example 1: Hide spurious underflow floating-point exceptions.
#include <fenv.h>
double f(double x)
{
# pragma STDC FENV_ACCESS ON
double result;
fenv_t save_env;
feholdexcept(&save_env);
// compute result
if (/* test spurious underflow */)
feclearexcept(FE_UNDERFLOW);
feupdateenv(&save_env);
return result;
}
ATTRIBUTES
See
attributes(7) for descriptions of the following attributes:
+----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+----------------------------+-----------------------------+
|Interface Stability | Standard |
+----------------------------+-----------------------------+
|MT-Level | MT-Safe |
+----------------------------+-----------------------------+
SEE ALSO
fenv.h(3HEAD),
fegetenv(3M),
feholdexcept(3M),
attributes(7),
standards(7)NOTES
In a multithreaded program, the
feupdateenv() function affects the
floating point environment only for the calling thread.
When the
FEX_CUSTOM handling mode is in effect for an exception,
raising that exception using
feupdateenv() causes the handling
function to be invoked. The handling function can then modify the
exception flags to be set as described in
fex_set_handling(3M). Any
result value the handler supplies will be ignored.
The
feupdateenv() function automatically installs and deinstalls
SIGFPE handlers and sets and clears the trap enable mode bits in the
floating point status register as needed. If a program uses these
functions and attempts to install a
SIGFPE handler or control the
trap enable mode bits independently, the resulting behavior is not
defined.
As described in
fex_set_handling(3M), when a handling function
installed in
FEX_CUSTOM mode is invoked, all exception traps are
disabled (and will not be reenabled while
SIGFPE is blocked). Thus,
attempting to change the environment from within a handler by calling
fesetenv(3M) or
feupdateenv might not produce the expected results.
SunOS 5.11 July 12, 2006 FEUPDATEENV(3M)
