DragonFly On-Line Manual Pages


FEENABLEEXCEPT(3)     DragonFly Library Functions Manual     FEENABLEEXCEPT(3)

NAME

feenableexcept, fedisableexcept, fegetexcept -- floating-point exception masking

LIBRARY

Math Library (libm, -lm)

SYNOPSIS

#include <fenv.h> #pragma STDC FENV_ACCESS ON int feenableexcept(int excepts); int fedisableexcept(int excepts); int fegetexcept(void);

DESCRIPTION

The feenableexcept() and fedisableexcept() functions unmask and mask (respectively) exceptions specified in excepts. The fegetexcept() func- tion returns the current exception mask. All exceptions are masked by default. Floating-point operations that produce unmasked exceptions will trap, and a SIGFPE will be delivered to the process. By installing a signal han- dler for SIGFPE, applications can take appropriate action immediately without testing the exception flags after every operation. Note that the trap may not be immediate, but it should occur before the next floating- point instruction is executed. For all of these functions, the possible types of exceptions include those described in fenv(3). Some architectures may define other types of floating-point exceptions.

RETURN VALUES

The feenableexcept(), fedisableexcept(), and fegetexcept() functions return a bitmap of the exceptions that were unmasked prior to the call.

SEE ALSO

sigaction(2), feclearexcept(3), feholdexcept(3), fenv(3), feupdateenv(3)

BUGS

Functions in the standard library may trigger exceptions multiple times as a result of intermediate computations; however, they generally do not trigger spurious exceptions. No interface is provided to permit exceptions to be handled in nontrivial ways. There is no uniform way for an exception handler to access infor- mation about the exception-causing instruction, or to determine whether that instruction should be reexecuted after returning from the handler. DragonFly 4.1 March 16, 2005 DragonFly 4.1