[gtkmm] Why would c style file IO work and not c++ style?

[Mark Jones <mark jones106 verizon net>]

Ok, this has me very puzzled, if I change that file IO over to c style
IO, it works fine in either place (called from the menu item signal
handler or the dialog's button's signal handler).

Why would this matter?  The C++ IO code is just fine as far as I can
see, it works from the dialog, it works from the console/command line
test progrram I wrote, and I see nothing wrong with it.  The C code is
completely the same as it, just different IO functions.

Is this a bug in gtk or gtkmm?  I was starting to think it must have to
do with what thread was calling it (since it worked from the dialog and
not the main window, when the calling line was exactly the same, and I
assume there are multiple threads inside gtk/gtkmm).  Now that c style
IO works, I don't suspect a thread so much anymore...I don't know what
to suspect.

Mark

Modified code shown below, if you want to run it, comment one section or
the other out completely.  Currently the c++ style IO is commented out.

bool saveFile( const std::string fileName, 
               const std::string textToWrite )
{

/*=-=-=-=-
    // This causes a hang if called from a menu item signal handler
-------
    //
--------------------------------------------------------------------
    ofstream outFile;
    outFile.open( fileName.c_str(), ios::out|ios::binary );
    if( outFile.bad() )
    {
        cerr << "Unable to open " << fileName << endl;
        return false;
    }

    cout << "Writing out: " << fileName << endl;

    outFile.write( textToWrite.c_str(), textToWrite.length() );

    cout << fileName << " writen out!" << endl;
    
    outFile.close();
=-=-=-=-*/

    // This does not causes a hang if called from a menu item signal
handler
    //
--------------------------------------------------------------------

    FILE *outFile;

    if( ( ( outFile = fopen( fileName.c_str(), "wb" ) ) == NULL ) )
    {
        cerr << "Unable to open " << fileName << endl;
        return false;
    }

    cout << "Writing out: " << fileName << endl;

    fwrite( textToWrite.c_str(), textToWrite.length(), 1, outFile );

    cout << fileName << " writen out!" << endl;

    fclose( outFile );    

    return true;
}




On Mon, 2002-12-16 at 14:08, Mark Jones wrote:
> I have created a very short and simple demonstration of the problem.  I
> have attached it to this e-mail.
> 
> To see this work after reviwing it, compiling it and starting it:
> 
> 1st
> 
> view->preferences
> save
> note output in console window where you started the program from
> in another window, view contents of "test" which is the file it creates
> AND DEFINITELY RUN THIS IN ITS OWN DIRECTORY SO YOU DON'T CLOBBER A FILE
> NAMED TEST IN YOUR DIRECTORY  :)
> 
> 2nd
> file->save
> note hang, note output in console window (compare to myFileWriter.cc to
> see where it hangs)
> in another window, view contents of "test" which is the file it creates
> 
> 3rd
> restart it
> file->save
> note hang
> in another window, view contents of "test" which is the file it creates
> 
> Note the text area is just there in both the main window and dialog, it
> doesn't actually do anything with it, even during the save.
> 
> Can anyone see what is wrong?
> 
> Mark
> 
> On Mon, 2002-12-16 at 01:55, Mark Jones wrote:
> > I have run into something very strange.  I have a file writer, and I can
> > use that file writer to write to a file when I call it from the signal
> > handler for a button that is on my own dialog (and the dialog is brought
> > up by a signal handler for a menu item in my application).  However, if
> > I try to do the same thing from the signal handler from my File->Save
> > menu item, it hangs the application (it is freezing on the first
> > ofstream::write() call).  Is there something special I need to do to
> > write to files from different places in a gtkmm program?
> > 
> > The file writer is fine I think because it works when called from the
> > dialog and in a command line driver program I wrote to test it.
> > 
> > Any ideas of what is going on?
> > 
> > Thanks!
> > 
> > Mark