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 float‐
       ing-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 under‐
       flow 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),	 stan‐
       dards(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,	 rais‐
       ing  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 dis‐
       abled (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			  12 Jul 2006		       feupdateenv(3M)

Vote for polarhome