NAME

fegetenv, feholdexcept, fesetenv, feupdateenv — manage floating-point environment

SYNOPSIS

Math Library (libm, -lm)
#include <fenv.h>

int
fegetenv(fenv_t *envp);

int
feholdexcept(fenv_t *envp);

int
fesetenv(const fenv_t *envp);

int
feupdateenv(const fenv_t *envp);

DESCRIPTION

These functions manage the floating-point environment — status flags, rounding direction modes and exception masks — as one entity. The envp input argument is an object representing the floating-point environment. The macro FE_DFL_ENV represents the default floating-point environment — the one installed at program startup.

The fegetenv() function stores the current floating-point environment in the object pointed to by envp.

The feholdexcept() function saves the current floating-point environment in the object pointed to by envp, clears the floating-point status flags, and then installs a non-stop (continue on floating-point exceptions) mode for all floating-point exceptions.

The fesetenv() function establishes the floating-point environment represented by the object pointed to by envp. The argument envp shall point to an object set by a call to fegetenv() or feholdexcept(), or equal the macro FE_DFL_ENV. Note that fesetenv() merely installs the state of the floating-point status flags represented through its argument, and does not raise these floating-point exceptions.

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

RETURN VALUES

The fegetenv(), feholdexcept(), fesetenv(), and feupdateenv() functions return zero on success, and non-zero if an error occurred.

SEE ALSO

feclearexcept(3), feenableexcept(3), fegetround(3)

STANDARDS

The fegetenv(), feholdexcept(), fesetenv(), and feupdateenv() functions conform to ISO/IEC 9899:1999 (“ISO C99”).

The return types for fegetenv(), fesetenv(), and feupdateenv() are int for alignment with ISO/IEC 9899:1999 (“ISO C99”) Defect Report #202.