feenableexcept(3) - NetBSD Manual Pages

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FEENABLEEXCEPT(3)       NetBSD 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.

NetBSD 9.1                      March 16, 2005                      NetBSD 9.1