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  excep-
       tions.  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(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |MT-Safe			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       fegetenv(3M), feholdexcept(3M), fenv.h(3HEAD), attributes(5), standards(5)

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 fes-
       etenv(3M) or feupdateenv might not produce the expected results.

SunOS 5.11							    12 Jul 2006 						   feupdateenv(3M)