feupdateenv(3p) — Linux manual page

FEUPDATEENV(3P)         POSIX Programmer's Manual        FEUPDATEENV(3P)

PROLOG

       This manual page is part of the POSIX Programmer's Manual.  The
       Linux implementation of this interface may differ (consult the
       corresponding Linux manual page for details of Linux behavior),
       or the interface may not be implemented on Linux.

NAME

       feupdateenv — update floating-point environment

SYNOPSIS

       #include <fenv.h>

       int feupdateenv(const fenv_t *envp);

DESCRIPTION

       The functionality described on this reference page is aligned
       with the ISO C standard. Any conflict between the requirements
       described here and the ISO C standard is unintentional. This
       volume of POSIX.1‐2017 defers to the ISO C standard.

       The feupdateenv() function shall attempt to save the currently
       raised floating-point exceptions in its automatic storage,
       attempt to install the floating-point environment represented by
       the object pointed to by envp, and then attempt to raise the
       saved floating-point exceptions. The argument envp shall point to
       an object set by a call to feholdexcept() or fegetenv(), or equal
       a floating-point environment macro.

RETURN VALUE

       The feupdateenv() function shall return a zero value if and only
       if all the required actions were successfully carried out.

ERRORS

       No errors are defined.

       The following sections are informative.

EXAMPLES

       The following example shows sample code to 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;
           }

APPLICATION USAGE

       None.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       fegetenv(3p), feholdexcept(3p)

       The Base Definitions volume of POSIX.1‐2017, fenv.h(0p)

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic
       form from IEEE Std 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 by the Institute of Electrical and Electronics
       Engineers, Inc and The Open Group.  In the event of any
       discrepancy between this version 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 .

       Any typographical or formatting errors that appear in this page
       are most likely to have been introduced during the conversion of
       the source files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group               2017                   FEUPDATEENV(3P)

Pages that refer to this page: fenv.h(0p), fegetenv(3p), feholdexcept(3p)

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