'\" te
.\" Copyright (c) 2001, the Institute of Electrical and Electronics Engineers, Inc. and The Open Group. All Rights Reserved.
.\" Portions Copyright (c) 2006, Sun Microsystems, Inc. All Rights Reserved.
.\"  Sun Microsystems, Inc. gratefully acknowledges The Open Group for permission to reproduce portions of its copyrighted documentation. Original documentation from The Open Group can be obtained online at  http://www.opengroup.org/bookstore/.
.\" The Institute of Electrical and Electronics Engineers and The Open Group, have given us permission to reprint portions of their documentation. In the following statement, the phrase "this text" refers to portions of the system documentation. Portions of this text are reprinted and reproduced in electronic form in the Sun OS Reference Manual, from IEEE Std 1003.1, 2004 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2004 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between these versions and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html.  This notice shall appear on any product containing this material. 
.TH feupdateenv 3M "12 Jul 2006" "SunOS 5.11" "Mathematical Library Functions"
.SH NAME
feupdateenv \- update floating-point environment
.SH SYNOPSIS
.LP
.nf
c99 [ \fIflag\fR... ] \fIfile\fR... \fB-lm\fR [ \fIlibrary\fR... ]
#include <fenv.h>

\fBint\fR \fBfeupdateenv\fR(\fBconst fenv_t *\fR\fIenvp\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBfeupdateenv()\fR 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 \fIenvp\fR, and then attempts to raise the saved floating-point exceptions. The \fIenvp\fR argument points to an object set by a call to \fBfegetenv\fR(3M) or \fBfeholdexcept\fR(3M), or equals a floating-point environment macro.
.SH RETURN VALUES
.sp
.LP
The \fBfeupdateenv()\fR function returns 0 if and only if all the required actions were successfully carried out.
.SH ERRORS
.sp
.LP
No errors are defined.
.SH EXAMPLES
.sp
.LP
The following example demonstrates sample code to hide spurious underflow floating-point exceptions:
.LP
\fBExample 1 \fRHide spurious underflow floating-point exceptions.
.sp
.in +2
.nf
#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;
}
.fi
.in -2

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
tab() box;
cw(2.75i) |cw(2.75i) 
lw(2.75i) |lw(2.75i) 
.
ATTRIBUTE TYPEATTRIBUTE VALUE
_
Interface StabilityCommitted
_
MT-LevelMT-Safe
_
StandardSee \fBstandards\fR(5).
.TE

.SH SEE ALSO
.sp
.LP
\fBfegetenv\fR(3M), \fBfeholdexcept\fR(3M), \fBfenv.h\fR(3HEAD), \fBattributes\fR(5), \fBstandards\fR(5)
.SH NOTES
.sp
.LP
In a multithreaded program, the \fBfeupdateenv()\fR function affects the floating point environment only for the calling thread.
.sp
.LP
When the \fBFEX_CUSTOM\fR handling mode is in effect for an exception, raising that exception using \fBfeupdateenv()\fR causes the handling function to be invoked. The handling function can then modify the exception flags to be set as described in \fBfex_set_handling\fR(3M).  Any result value the handler supplies will be ignored.
.sp
.LP
The \fBfeupdateenv()\fR function automatically installs and deinstalls \fBSIGFPE\fR 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 \fBSIGFPE\fR handler or control the trap enable mode bits independently, the resulting behavior is not defined.
.sp
.LP
As described in \fBfex_set_handling\fR(3M), when a handling function installed in \fBFEX_CUSTOM\fR mode is invoked, all exception traps are disabled (and will not be reenabled while \fBSIGFPE\fR is blocked). Thus, attempting to change the environment from within a handler by calling \fBfesetenv\fR(3M) or \fBfeupdateenv\fR might not produce the expected results.