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



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

NNAAMMEE
       feupdateenv -- update floating-point environment

SSYYNNOOPPSSIISS
       #include <fenv.h>

       int feupdateenv(const fenv_t *_e_n_v_p);

DDEESSCCRRIIPPTTIIOONN
       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 _f_e_u_p_d_a_t_e_e_n_v() 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
       _e_n_v_p, and then attempt to raise the saved floating-point exceptions.
       The argument _e_n_v_p shall point to an object set by a call to
       _f_e_h_o_l_d_e_x_c_e_p_t() or _f_e_g_e_t_e_n_v(), or equal a floating-point environment
       macro.

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

EERRRROORRSS
       No errors are defined.

       _T_h_e _f_o_l_l_o_w_i_n_g _s_e_c_t_i_o_n_s _a_r_e _i_n_f_o_r_m_a_t_i_v_e_.

EEXXAAMMPPLLEESS
       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;
           }

AAPPPPLLIICCAATTIIOONN UUSSAAGGEE
       None.

RRAATTIIOONNAALLEE
       None.

FFUUTTUURREE DDIIRREECCTTIIOONNSS
       None.

SSEEEE AALLSSOO
       _f_e_g_e_t_e_n_v(), _f_e_h_o_l_d_e_x_c_e_p_t()

       The Base Definitions volume of POSIX.1-2017, <<ffeennvv..hh>>

CCOOPPYYRRIIGGHHTT
       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(3)
