Re: Runtime error reporting

From: williamkempf_at_[hidden]
Date: 2001-03-20 16:43:47

--- In boost_at_y..., Gary Powell <Gary.Powell_at_s...> wrote:
> >>
> > Taking Win32 API as an example, in theory almost every function 
call there
> > can fail, and consistent checking for it really helps to detect 
induced
> > errors (and their sources, of course). The problem with having 
only
> > classic
> > 'assert'-like macro as a checking tool for such errors is that 
consistent
> > application of "check a return value of every API function call" 
policy
> > makes your code much more bloated and clumsy, e.g.:
> > 
> > void clipboard::put_text(std::string const& text) {
> >   HGLOBAL handle = ::GlobalAlloc( GHND, text.length() + 1 );
> >   // copy text to allocated memory
> >   // ..
> >   // copy text to clipboard
> >   bool result1 = ::OpenClipboard(0);
> >   assert(result1);
> >   bool result2 = ::EmptyClipboard();
> >   assert(result2);
> >   bool result3 = ::SetClipboardData(CF_TEXT, handle);
> >   assert(result3);
> >   bool result4 = ::CloseClipboard();
> >   assert(result4);
> > }
> > 
> > vs.
> > 
> > void clipboard::put_text(std::string const& text) {
> >   HGLOBAL handle = ::GlobalAlloc( GHND, text.length() + 1 );
> >   // copy text to allocated memory
> >   // ..
> >   // copy text to clipboard
> >   sys_verify(::OpenClipboard(0));
> >   sys_verify(::EmptyClipboard());
> >   sys_verify(::SetClipboardData(CF_TEXT, handle));
> >   sys_verify(::CloseClipboard());
> > }
> > 
> > You can beautify the first version a little by rearranging the 
code like
> > this:
> > 
> >   { bool result = ::OpenClipboard(0); assert(result); }
> >   { bool result = ::EmptyClipboard(); assert(result); }
> >   // etc.
> > 
> > but IMO 'sys_verify' version is still much more appealing here.
> <<
> IMO this sort of API cries out for exceptions.
> 
> void foo ()
> {
>   try {
>      put_text(TextString);
>  }
>  catch (TextErrors &terr)
>  {
>    // do something useful here with terr.
>  }
>  // let unknown errors percolate up the stack.

I don't see how put_text differs any from the thread implementation 
that I had *thought* was decided should use assertions.

Bill Kempf