fegetenv, feholdexcept, fesetenv, feupdateenv - floating-point environment save and restore

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.Lb libm

.In fenv.h
.Fd #pragma STDC FENV_ACCESS ON int fegetenv fenv_t *envp int feholdexcept fenv_t *envp int fesetenv const fenv_t *envp int feupdateenv const fenv_t *envp

The floating-point environment includes exception flags and masks, the current rounding mode, and other architecture-specific settings. However, it does not include the floating-point register file.

The fegetenv function stores the current floating-point environment in the object pointed to by envp, whereas feholdexcept saves the current environment, then clears all exception flags and masks all floating-point exceptions.

The fesetenv function restores a previously saved environment. The feupdateenv function restores a saved environment as well, but it also raises any exceptions that were set in the environment it replaces.

The feholdexcept function is often used with feupdateenv or fesetenv to suppress spurious exceptions that occur as a result of intermediate computations. An example in fenv(3) demonstrates how to do this.

The fegetenv, feholdexcept, fesetenv, and feupdateenv functions return 0 if they succeed, and non-zero otherwise.

feclearexcept(3), fenv(3), feraiseexcept(3), fesetenv(3), fetestexcept(3), fpgetmask(3), fpgetprec(3), fpsetmask(3), fpsetprec(3)

The fegetenv, feholdexcept, fesetenv, and feupdateenv functions conform to -isoC-99.

These routines first appeared in
.Fx 5.3 .

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