Re: advice on best use of try catch throw
aao wrote:
Send message is really not a good example, return value depends on the
message and GetError might indicate some minor problem in underling calls,
but yes you example will do
It makes sense in some context like :
void GetRect(RECT& rc) throw(CError &)
{
assert(::IsWindow(m_hWnd));
if(!:: GetWindowRect(m_hWnd, & rc))
throw(CError(GetLastError()));
}
FYI: exception specifications are a bad idea in general. The reason is that
the compiler is required to filter out all but the given exceptions and
invoke std::unexpected, which presents an additional overhead.
//my preference still would be(it does not force you user into emergency
recovery mode) :
HRESULT GetRect(RECT& rc)
{
assert(::IsWindow(m_hWnd));
if(!:: GetWindowRect(m_hWnd, & rc))
return HRESULT_FROM_WIN32(GetLastError());
return S_OK;
}
- I can't initialise a constant with the result of this function.
- It forces me to clutter my logic with the checking of returnvalues, i.e.
this is a maintenance overhead.
- It encourages less good programmers to ignore possible errors.
- Recurring checks of returnvalues are an unnecessary performance overhead.
- Exception can carry much more information than a HRESULT. If you replace
it with a different struct, the performance penalty increases further.
That said, there is also Boost.Optional:
boost::optional<CRect>
GetRect() {
CRect rc;
if( ::IsWindow(m_hWnd)
&& ::GetWindowRect( m_hWnd, &rc))
return rc;
return boost::none;
}
I would go for an assertion though, and require the programmer to check
first that the object is really associated with a window. IOW, I would
declare a failure to be a programming error.
Uli