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__SETFPUCW

Section: Linux Programmer's Manual (3)
Updated: 2017-09-15
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NAME

__setfpucw - set FPU control word on i386 architecture (obsolete)

SYNOPSIS

#include <i386/fpu_control.h>

void __setfpucw(unsigned short control_word);

DESCRIPTION

__setfpucw() transfers control_word to the registers of the FPU (floating-point unit) on the i386 architecture. This was used to control floating-point precision, rounding and floating-point exceptions.

CONFORMING TO

This function was a nonstandard GNU extension.

NOTES

As of glibc 2.1 this function does not exist anymore. There are new functions from C99, with prototypes in <fenv.h>, to control FPU rounding modes, like fegetround(3), fesetround(3), and the floating-point environment, like fegetenv(3), feholdexcept(3), fesetenv(3), feupdateenv(3), and FPU exception handling, like feclearexcept(3), fegetexceptflag(3), feraiseexcept(3), fesetexceptflag(3), and fetestexcept(3).

If direct access to the FPU control word is still needed, the _FPU_GETCW and _FPU_SETCW macros from <fpu_control.h> can be used.

EXAMPLE

__setfpucw(0x1372)

Set FPU control word on the i386 architecture to

     - extended precision

     - rounding to nearest

     - exceptions on overflow, zero divide and NaN

COLOPHON

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