feenableexcept(3) [netbsd man page]
FEENABLEEXCEPT(3) BSD 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 handler 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 information about the exception-causing instruction, or to determine whether that instruction should be reexecuted after returning from the handler. BSD
March 16, 2005 BSD
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FECLEAREXCEPT(3) BSD Library Functions Manual FECLEAREXCEPT(3) NAME
feclearexcept, fegetexceptflag, feraiseexcept, fesetexceptflag, fetestexcept -- floating-point exception flag manipulation LIBRARY
Math Library (libm, -lm) SYNOPSIS
#include <fenv.h> #pragma STDC FENV_ACCESS ON int feclearexcept(int excepts); int fegetexceptflag(fexcept_t *flagp, int excepts); int feraiseexcept(int excepts); int fesetexceptflag(const fexcept_t *flagp, int excepts); int fetestexcept(int excepts); DESCRIPTION
The feclearexcept() routine clears the floating-point exception flags specified by excepts, whereas feraiseexcept() raises the specified exceptions. Raising an exception causes the corresponding flag to be set, and a SIGFPE is delivered to the process if the exception is unmasked. The fetestexcept() function determines which flags are currently set, of those specified by excepts. The fegetexceptflag() function stores the state of the exception flags specified in excepts in the opaque object pointed to by flagp. Simi- larly, fesetexceptflag() changes the specified exception flags to reflect the state stored in the object pointed to by flagp. Note that the flags restored with fesetexceptflag() must be a (not necessarily proper) subset of the flags recorded by a prior call to fegetexceptflag(). 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. IMPLEMENTATION NOTES
On some architectures, raising an overflow or underflow exception also causes an inexact exception to be raised. In these cases, the over- flow or underflow will be raised first. The fegetexceptflag() and fesetexceptflag() routines are preferred to fetestexcept() and feraiseexcept(), respectively, for saving and restoring exception flags. The latter do not re-raise exceptions and may preserve architecture-specific information such as addresses where exceptions occurred. RETURN VALUES
The feclearexcept(), fegetexceptflag(), feraiseexcept(), and fesetexceptflag() functions return 0 upon success, and non-zero otherwise. The fetestexcept() function returns the bitwise OR of the values of the current exception flags that were requested. SEE ALSO
sigaction(2), feholdexcept(3), fenv(3), feupdateenv(3), fpgetsticky(3) STANDARDS
The feclearexcept(), fegetexceptflag(), feraiseexcept(), fesetexceptflag(), and fetestexcept() routines conform to ISO/IEC 9899:1999 (``ISO C99''). HISTORY
These functions first appeared in FreeBSD 5.3 and NetBSD 6.0. BSD
May 8, 2004 BSD