Ada.Text_IO paired with mwindows switch (msys2)

General
1

Using the -mwindows switch with an application that uses Ada.Text_IO seemingly causes the application to either exit / exception out. I was wondering if anyone knew of another switch that I could pair with this to allow the program to run. The text_io stuff is just for debug, so I only specify the -mwindows switch in release mode, but I do want it to spawn the console and print stuff in debug mode.

2

The switch is used for GUI applications. If you want a console application then you need to omit the switch.

A GUI process is normally spawned without standard files. The Ada.Text_IO error comes from there. You can start a GUI application manually in a way that it would have the standard output/error passed to the process. For example under a console:

> my_program.exe > output.txt >2&1

GPS catches the output and error you start a GUI application from under it.

Then for debug purpose it is best to use tracing into an external file. Otherwise use a MessageBox (Win32 API). In GtkAda you can use:

   procedure Say
             (  Message       : UTF8_String;
                Title         : UTF8_String := "";
                Mode          : UTF8_String := Stock_Dialog_Info;
                Justification : Gtk_Justification := Justify_Left;
                Parent        : access Gtk_Widget_Record'Class := null
             );
1 Like
3

Thanks, I’m aware of this. I wanted to do it as a console application when not compiled for “release” (some things happen before the GUI starts, and I would like to see debug on them) but also spawn it as only a GUI application when compiled for “release”.

I was hoping to avoid having to do a log file if possible, so I was wondering if there were any switches to tell GNAT the intention there.

4

Simply remove -mwindows in the debug build. That will open a console upon application start.

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5

Yep, that’s what I’m doing, the problem is the debug statements cause the application to crash when in “release” mode with -mwindows specified, so I think GNAT doesn’t handle it well with that switch if one does use Ada.Text_IO for debugging.

I was hoping the Put_Line’s and such would just silently get eaten when -mwindows is specified, but they cause exceptions instead.

6

Don’t you see an irony here? :grinning:

GNAT has nothing to do with any of that. This is a Windows behaviour per design. It is not even MSYS, if you linked it using MS-linker you would get exactly same behaviour.

1 Like
7

You can use VSS.Text_Streams.Standards.Output_Stream instead, it outputs to stdout when it is available and do nothing otherwise.

8

Thanks. That’s kind of the way I am currently going. I can’t get VSS, but I’m emulating the same thing using pragma Debug and wrapping that in a function for now.

Just to reiterate: