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HP-UX 11i Version 3: February 2007

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feupdateenv() — update floating-point environment


#include <fenv.h>

HP Integrity Server Only

int feupdateenv(const fenv_t *envp);


void feupdateenv(const fenv_t *envp);


The feupdateenv() function saves the currently raised floating-point exceptions in its automatic storage, installs the floating-point environment represented by the object pointed to by envp, and then raises the saved floating-point exceptions. Use feholdexcept() with feupdateenv() to hide spurious floating-point exceptions.

The argument envp must point to an object set by a call to fegetenv() or feholdexcept(), or equal the macro FE_DFL_ENV.


To use this function, compile either with the default -Ae option or with the -Aa and -D_HPUX_SOURCE options. Make sure your program includes <fenv.h>.

For Integrity servers, specify +Ofenvaccess on the compiler command line or place the call to this function under the effect of an affirmative FENV_ACCESS pragma:


If the FENV_ACCESS pragma is placed outside of any top-level declarations in a file, the pragma will apply to all declarations in the compilation following the pragma until another FENV_ACCESS pragma is encountered or until the end of the file is reached.

If the FENV_ACCESS pragma is placed at the beginning of a block (compound statement), the pragma will apply until another FENV_ACCESS pragma is encountered or until the end of the block is reached.

For PA-RISC, you might need to use the +Onomoveflops compiler option in order to prevent optimizations that can undermine the specified behavior of this function.

Link in the math library by specifying -lm on the compiler or linker command line.

For more information, see the HP-UX floating-point guide for HP Integrity servers at the following site: http://www.hp.com/go/fp.


Integrity Server Only

This function always returns 0, indicating that all the actions were successfully carried out.




No errors are defined.


Store the current floating-point environment in holdenv, hide spurious underflow exceptions, and continue on any floating-point exceptions that occur until the call to feupdateenv() is encountered.

#include <fenv.h> /*...*/ fenv_t holdenv; feholdexcept(&holdenv); /* perform operations */ if (/* test for spurious underflow */) feclearexcept(FE_UNDERFLOW); feupdateenv(&holdenv); /* raise accumulated exceptions */


feupdateenv() : ISO/IEC C99 (including Annex F, "IEC 60559 floating-point arithmetic")

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