Re: gnuplot on 64-bit Windows

[sfeam (E. Merritt) <eam...@gm...>]

On Wednesday, 24 July 2013, Allin Cottrell wrote:
> On Wed, 24 Jul 2013, sfeam (Ethan Merritt) wrote:
> 
> > On Wednesday, 24 July 2013, Allin Cottrell wrote:
> >> I have need of a 64-bit Windows build of gnuplot and I've been
> >> working on cross-compiling from Linux using mingw64. I see
> >> several places in current CVS where the code generates errors
> >> and warnings. I'm attaching a patch-set which quells the
> >> errors and warnings, but unfortunately I'm not able to test on
> >> win64 at present.
> >
> > I can't help with evaluation of the full patch, but one set of
> > changes strikes me as being wrong on the face of it:
> >
> > %%%%%%%%%%%%%%
> > +#ifdef _WIN64
> > +INT_PTR CALLBACK PrintDlgProc(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam);
> > +#else
> > BOOL CALLBACK PrintDlgProc(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam);
> > +#endif
> > %%%%%%%%%%%%%%
> >
> > There's no way it can be correct to label a Boolean value  as a pointer.
> >
> > The equivalent substitution occurs several places in your patch.
> > I didn't check each one, but the routine PrintDlgProc really does return
> > TRUE or FALSE, so I think at least in this case, if not all of them,
> > the original code was correct.
> 
> It's strange, I agree, but the original code throws a warning. 
> The caller, in all cases, is CreateDialogParam() and the 
> callback is the fourth argument, of type DLGPROC, in relation 
> to which the msdn doc points us to "DialogProc callback 
> function"
> 
> http://msdn.microsoft.com/en-us/library/windows/desktop/ms645469%28v=vs.85%29.aspx
> 
> where we find:
> 
> <quote>
> Return value
> 
> Type: INT_PTR
> 
> Typically, the dialog box procedure should return TRUE if it 
> processed the message, and FALSE if it did not. If the dialog 
> box procedure returns FALSE, the dialog manager performs the 
> default dialog operation in response to the message.
> </quote>

[shudder]
Nevertheless, wouldn't your change just shift the site of the
error/warning message?  Now the prototype says it returns
INT_PTR but the function itself still says it returns BOOL.
So there is still a mismatch in types.

I found a hideous example on that Microsoft site you linked to:
http://msdn.microsoft.com/en-us/library/windows/desktop/ff728900(v=vs.85).aspx

It declares a callback function
   INT_PTR CALLBACK OpenUrlDialogProc(HWND hDlg, UINT message, 
                                                                     WPARAM wParam, LPARAM lParam)
which exits with
   return (INT_PTR)FALSE;

I guess it's a matter of "choose your poison".

	Ethan



> It's probably OK to leave the code as is and ignore the 
> warning, but here it is:
> 
> ../src/win/wgraph.c: In function 'LineStyle':
> ../src/win/wgraph.c:3607:2: warning: passing argument 4 of 
> 'DialogBoxParamA' from incompatible pointer type [enabled by 
> default]
> /opt/win64/lib/gcc/x86_64-w64-mingw32/4.6.4/../../../../x86_64-w64-mingw32/include/winuser.h:2104:29: 
> note: expected 'DLGPROC' but argument is of type 'BOOL 
> (*)(struct HWND__ *, UINT,  WPARAM,  LPARAM)'
> 
> Allin Cottrell
>