// Declare an object of this type in a scope in order to suppress
// all floating-point exceptions temporarily. The old exception
// state will be reset at the end.
class FPExceptionDisabler
{
public:
FPExceptionDisabler()
{
// Retrieve the current state of the exception flags. This
// must be done before changing them. _MCW_EM is a bit
// mask representing all available exception masks.
_controlfp_s(&mOldValues, _MCW_EM, _MCW_EM);
// Set all of the exception flags, which suppresses FP
// exceptions on the x87 and SSE units.
_controlfp_s(0, _MCW_EM, _MCW_EM);
}
~FPExceptionDisabler()
{
// Clear any pending FP exceptions. This must be done
// prior to enabling FP exceptions since otherwise there
// may be a 'deferred crash' as soon the exceptions are
// enabled.
_clearfp();
// Reset (possibly enabling) the exception status.
_controlfp_s(0, mOldValues, _MCW_EM);
}
private:
unsigned int mOldValues;
// Make the copy constructor and assignment operator private
// and unimplemented to prohibit copying.
FPExceptionDisabler(const FPExceptionDisabler&);
FPExceptionDisabler& operator=(const FPExceptionDisabler&);
};
// Declare an object of this type in a scope in order to enable a
// specified set of floating-point exceptions temporarily. The old
// exception state will be reset at the end.
// This class can be nested.
class FPExceptionEnabler
{
public:
// Overflow, divide-by-zero, and invalid-operation are the FP
// exceptions most frequently associated with bugs.
FPExceptionEnabler(unsigned int enableBits = _EM_OVERFLOW |
_EM_ZERODIVIDE | _EM_INVALID)
{
// Retrieve the current state of the exception flags. This
// must be done before changing them. _MCW_EM is a bit
// mask representing all available exception masks.
_controlfp_s(&mOldValues, _MCW_EM, _MCW_EM);
// Make sure no non-exception flags have been specified,
// to avoid accidental changing of rounding modes, etc.
enableBits &= _MCW_EM;
// Clear any pending FP exceptions. This must be done
// prior to enabling FP exceptions since otherwise there
// may be a 'deferred crash' as soon the exceptions are
// enabled.
_clearfp();
// Zero out the specified bits, leaving other bits alone.
_controlfp_s(0, ~enableBits, enableBits);
}
~FPExceptionEnabler()
{
// Reset the exception state.
_controlfp_s(0, mOldValues, _MCW_EM);
}
private:
unsigned int mOldValues;
// Make the copy constructor and assignment operator private
// and unimplemented to prohibit copying.
FPExceptionEnabler(const FPExceptionEnabler&);
FPExceptionEnabler& operator=(const FPExceptionEnabler&);
};
