Re: RFC: gfortran on Windows - handling of no console / pausing before end-of-program console destruction

[Tim Zeisloft <tim at marlettesoftware dot com>]

Hi Tobias,

> The "no console available" implies that one passes this flag when one 
> compiles the Fortran main program, cf. 
> http://gcc.gnu.org/onlinedocs/gfortran/Non_002dFortran-Main-Program.html 
> - That flag only makes sense with Windows as there the ABI function is 
> automatically available and code is started without console. 
This is how current implementations I am aware of behave.

> It's not clear to me whether the option should be printed at startup 
> or when doing I/O to standard out/in (OUTPUT:_UNIT, INPUT_UNIT). The 
> former is simpler and faster, but has "false positive". The latter is 
> slower but hasn't.
I like taking care of it when the I/O occurs. It seems better to not 
make the compiler do things at startup to prepare for low-percentage 
situations.

> I think it should be silently accepted by the compiler on non-Windows 
> systems, even if it is in the library only available for MinGW, 
> MinGW-w64 and presumably Cygwin(64).
Agree.

> For pause on exit, it is not clear me whether that always triggers or 
> only when the console would otherwise close. If the latter, I wonder 
> who that's detectable from within the run-time library. (If one has to 
> modify MinGW and MinGW-w64, it would be more difficult - as one has 
> also get code into that library.) At least for a "only pause when the 
> console would otherwise close" feature, it would be Windows only. 
> However, one could implement it as always pause before exit on other 
> systems; the latter might be not often useful, but sometimes it could. 
> Thus, I think this option should be generally available - even if it 
> has slightly different run-time behaviour.
I am only familiar with the "pause before exit" behavior, and that is 
what I will implement, incorporating your suggestions.

> Regarding the name: "-fpause-on-exit" (= "--pause-on-exit") seems to 
> be fine. But "-ferror-messagebox" I find a bit misleading - but I 
> don't have a great suggestion. Maybe -fmsgbox-if-no-console?
Okay.

> For the implementation: On the compiler side, it has to be added to 
> lang.opt (options.c, gfortran.h) and trans-decl.c's 
> create_main_function. It has to be documented in gfortran's 
> invoke.texi and gfortran.texi's "Non-Fortran Main Program".
Thanks for these pointers.

Tim

On 5/26/2013 10:49 AM, Tobias Burnus wrote:
> On April 30, 2013 17:47, Tim Zeisloft wrote:
> > > A message box which gives the error messages from the console or 
> > > just an
> > > "automated pause" to not close the console would certainly help those
> > > users -
> > > > and probably not harm anyone else.
> > > I disagree with that. Although I see the value in a more "user 
> > > friendly"
> > > behavior on Windows w.r.t. console handling, one can argue whether 
> > > it should
> > > be handled by the compiler runtime or by the user program. And, more
> > > importantly, the runtime "user friendly interface" might interfere 
> > > with at
> > > least two types of usage:
> > >
> > >    1. power users, who have existing setups (including scripting, 
> > > automation,
> > > etc.)
> > >    2. large apps that have developped their own interface for this 
> > > purpose
> > >
> > > Anything that is done in gfortran should be, in my opinion, at least
> > > user-unselectable.
> >
> > It sounds like the consensus is that both these features could be 
> > useful for mingw targets provided they be made selectable. I am 
> > willing to implement this, though it might take a little while.
> > Would switches named --error-messagebox/--no-error-messagebox and 
> > --pause-on-exit/--no-pause-on-exit suffice?
>
> Sorry for the belated reply - I was busy with other things and kind of 
> forgot about this item. Additionally, I was hoping to see some reply 
> from others.
>
>
> The "no console available" implies that one passes this flag when one 
> compiles the Fortran main program, cf. 
> http://gcc.gnu.org/onlinedocs/gfortran/Non_002dFortran-Main-Program.html 
> - That flag only makes sense with Windows as there the ABI function is 
> automatically available and code is started without console. (For 
> Unix, a message box is not practical - already for dependency reasons. 
> I don't know whether the issue can occur on OSX/Darwin and whether 
> library dependency is an issue.) It's not clear to me whether the 
> option should be printed at startup or when doing I/O to standard 
> out/in (OUTPUT:_UNIT, INPUT_UNIT). The former is simpler and faster, 
> but has "false positive". The latter is slower but hasn't. I think it 
> should be silently accepted by the compiler on non-Windows systems, 
> even if it is in the library only available for MinGW, MinGW-w64 and 
> presumably Cygwin(64).
>
>
> For pause on exit, it is not clear me whether that always triggers or 
> only when the console would otherwise close. If the latter, I wonder 
> who that's detectable from within the run-time library. (If one has to 
> modify MinGW and MinGW-w64, it would be more difficult - as one has 
> also get code into that library.) At least for a "only pause when the 
> console would otherwise close" feature, it would be Windows only. 
> However, one could implement it as always pause before exit on other 
> systems; the latter might be not often useful, but sometimes it could. 
> Thus, I think this option should be generally available - even if it 
> has slightly different run-time behaviour.
>
>
> Regarding the name: "-fpause-on-exit" (= "--pause-on-exit") seems to 
> be fine. But "-ferror-messagebox" I find a bit misleading - but I 
> don't have a great suggestion. Maybe -fmsgbox-if-no-console?
>
> For the implementation: On the compiler side, it has to be added to 
> lang.opt (options.c, gfortran.h) and trans-decl.c's 
> create_main_function. It has to be documented in gfortran's 
> invoke.texi and gfortran.texi's "Non-Fortran Main Program".
>
> Tobias