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man pages section 3: Extended Library Functions, Volume 2

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Updated: Thursday, June 13, 2019
 
 

fesetenv(3M)

Name

fegetenv, fesetenv - get and set current floating-point environment

Synopsis

c99 [ flag... ] file... –lm [ library... ]
#include <fenv.h>

int fegetenv(fenv_t *envp);
int fesetenv(const fenv_t *envp);

Description

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

The fesetenv() function attempts to establish the floating-point environment represented by the object pointed to by envp. The envp argument points to an object set by a call to fegetenv() or feholdexcept(3M), or equals a floating-point environment macro. The fesetenv() function does not raise floating-point exceptions, but only installs the state of the floating-point status flags represented through its argument.

Return Values

If the representation was successfully stored, fegetenv() returns 0. Otherwise, it returns a non-zero value.

If the environment was successfully established, fesetenv() returns 0. Otherwise, it returns a non-zero value.

Errors

No errors are defined.

Attributes

See attributes(7) for descriptions of the following attributes:

ATTRIBUTE TYPE
ATTRIBUTE VALUE
Interface Stability
Committed
Availability
system/library/math
MT-Level
MT-Safe
Standard

See Also

fenv.h(3HEAD), feholdexcept(3M), feupdateenv(3M), attributes(7), standards(7)

Notes

In a multithreaded program, the fegetenv() and fegetenv() functions affect the floating point environment only for the calling thread.

These functions automatically install and deinstall SIGFPE handlers and set and clear 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 disabled (and will not be reenabled while SIGFPE is blocked). Thus, attempting to change the environment from within a handler by calling fesetenv or feupdateenv(3M) might not produce the expected results.