Re: Having a problem building with win32ada

[John McCabe <john@nospam.assen.demon.co.uk.nospam>]

Guys

Thought I might as well add it to this thread, but I'm now having a
slight problem running with Win32Ada.

The basis of the code I'm using is in my "please review my code"
thread.

Essentially I've got the code shown below the double dashed line
(well, that's most of it).

When I run it, the Read_And_Print_Patches call _before_ outputting the
output device information is fine, but the same call _after_
outputting the output device information fails. Sometimes it just
prints the "1" prior to the Ada.Text_IO.Open call, and sometimes I get
PROGRAM_ERROR EXCEPTION_ACCESS_VIOLATION.

Now, if I change the declarations of Midi_In_Caps and Midi_Out_Caps
to:

   Midi_In_Caps  : aliased Win32.Mmsystem.MIDIINCAPS;
   Midi_Out_Caps : aliased Win32.Mmsystem.MIDIOUTCAPS;

and use 'Unchecked_Access in the calls to midiInGetDevCaps and
midiOutGetDevCaps for those objects (and dispose of the Free calls) it
seems to work ok. That sounds like some memory isn't being allocated
properly somehow. I can't see that I'm doing anything wrong but if you
can please let me know.

One thing I noticed though is that in mmsystem.h (in the
i686-pc-mingw32 folder) the declaration of MIDIINCAPS (well,
MIDIINCAPSA as it's non-Unicode) is:

   typedef struct tagMIDIINCAPSA {
       WORD wMid;
       WORD wPid;
       MMVERSION vDriverVersion;
       CHAR szPname[MAXPNAMELEN];
       DWORD dwSupport;
   } MIDIINCAPSA,*PMIDIINCAPSA,*LPMIDIINCAPSA;

However in win32-mmsystem.ads, the corresponding definition is:

   type MIDIINCAPSA is                          --  mmsystem.h:835
      record
         wMid : Win32.WORD;                     --  mmsystem.h:836
         wPid : Win32.WORD;                     --  mmsystem.h:837
         vDriverVersion : MMVERSION;            --  mmsystem.h:838
         szPname : Win32.CHAR_Array (0 .. 31);  --  mmsystem.h:839
      end record;

Now call me stupid if you like, but does it not look like there's
something missing there? (i.e. the dwSupport field).

If anyone can be bothered to check this out and see what they think
your comments would be appreciated, especially if you can spot that
I've done something stupid.

Do you think this is a bug that AdaCore should know about if they
don't already?

Obviously I could go down the route of not using dynamic memory
because, as I mentioned, it seems to work that way, but I don't like
not knowing why it didn't work the other way!

=================================
-- File: MidiDevs.adb
with Ada.Text_IO;
with Ada.Unchecked_Deallocation;

with Interfaces.C;
use type Interfaces.C.Unsigned;

with Win32.Mmsystem;
use type Win32.Mmsystem.MMRESULT;

with TestFileRead;

procedure MidiDevs is
   Num_Input_Devices  : Win32.UINT;
   Num_Output_Devices : Win32.UINT;

   res           : Win32.Mmsystem.MMRESULT;
   Midi_In_Caps  : Win32.Mmsystem.LPMIDIINCAPS;
   Midi_Out_Caps : Win32.Mmsystem.LPMIDIOUTCAPS;

   procedure Free is new
      Ada.Unchecked_Conversion(Win32.Mmsystem.LPMIDIINCAPS,
                               Win32.Mmsystem.MIDIINCAPS);
   procedure Free is new
      Ada.Unchecked_Conversion(Win32.Mmsystem.LPMIDIOUTCAPS,
                               Win32.Mmsystem.MIDIOUTCAPS);

   package UINT_Text_IO is new
      Ada.Text_IO.Modular_IO(Win32.UINT);
   package MM_Text_IO is new
      Ada.Text_IO.Modular_IO(Win32.Mmsystem.MMRESULT);

begin
   Num_Input_Devices := Win32.Mmsystem.midiInGetNumDevs;
   Num_Output_Devices := Win32.Mmsystem.midiOutGetNumDevs;

   Ada.Text_IO.Put("There are ");
   UINT_Text_IO.Put(Num_Input_Devices, 0);
   Ada.Text_IO.Put(" input devices available, and ");
   UINT_Text_IO.Put(Num_Output_Devices, 0);
   Ada.Text_IO.Put_Line(" output devices available.");

   Midi_In_Caps  := new Win32.Mmsystem.MIDIINCAPS;
   Midi_Out_Caps := new Win32.Mmsystem.MIDIOUTCAPS;

   if Num_Input_Devices > 0
   then
      Ada.Text_IO.New_Line;
      Ada.Text_IO.Put("The ");
      UINT_Text_IO.Put(Num_Input_Devices, 0);
      Ada.Text_IO.Put_Line(" input devices are:");
      Ada.Text_IO.New_Line;

      for Device_ID in Win32.UINT range 0..(Num_Input_Devices - 1)
      loop
         res := Win32.Mmsystem.midiInGetDevCaps(Device_ID,
                                                Midi_In_Caps,

Win32.Mmsystem.MIDIINCAPS'size
                                                   * Win32.BYTE'size);
         UINT_Text_IO.Put(Device_ID, 0);
         Ada.Text_IO.Put(") ");
         if res = Win32.Mmsystem.MMSYSERR_NOERROR
         then
            Ada.Text_IO.Put("szPname = ");

Ada.Text_IO.Put_Line(Interfaces.C.To_Ada(Win32.To_C(Midi_In_Caps.szPname)));
         else
            Ada.Text_IO.Put("Query Failed. Returned ");
            MM_Text_IO.Put(res, 0);
         end if;
         Ada.Text_IO.New_Line;
      end loop;
   end if;

   -- Try reading in the file
   TestFileRead.Read_And_Print_Patches;
   Ada.Text_IO.New_Line;

   if Num_Output_Devices > 0
   then
      Ada.Text_IO.New_Line;
      Ada.Text_IO.Put("The ");
      UINT_Text_IO.Put(Num_Output_Devices, 0);
      Ada.Text_IO.Put_Line(" output devices are:");
      Ada.Text_IO.New_Line;

      for Device_ID in Win32.UINT range 0..(Num_Output_Devices - 1)
      loop
         res := Win32.Mmsystem.midiOutGetDevCaps(Device_ID,
                                                 Midi_Out_Caps,

Win32.Mmsystem.MIDIOUTCAPS'size
                                                   * Win32.BYTE'size);
         UINT_Text_IO.Put(Device_ID, 0);
         Ada.Text_IO.Put(") ");
         if res = Win32.Mmsystem.MMSYSERR_NOERROR
         then
            Ada.Text_IO.Put("szPname = ");

Ada.Text_IO.Put_Line(Interfaces.C.To_Ada(Win32.To_C(Midi_Out_Caps.szPname)));
         else
            Ada.Text_IO.Put("Query Failed. Returned ");
            MM_Text_IO.Put(res, 0);
         end if;
         Ada.Text_IO.New_Line;
      end loop;
   end if;

   -- Try reading in the file
   TestFileRead.Read_And_Print_Patches;
   Ada.Text_IO.New_Line;

   Free(Midi_In_Caps);
   Free(Midi_Out_Caps);

end MidiDevs;
===================
=================================
-- File: TestFileRead.ads
package TestFileRead is
   procedure Read_And_Print_Patches;
end TestFileRead;
===================
=================================
-- File: TestFileRead.adb
with Ada.Text_IO;

package body TestFileRead is
   ----------------------------
   -- Read_And_Print_Patches --
   ----------------------------
   procedure Read_And_Print_Patches is
      Input_File : Ada.Text_IO.File_Type;
   begin
      Ada.Text_IO.Put_Line("1");
      -- Note: You need a file that exists
      Ada.Text_IO.Open(SysEx_File,
                       Ada.Text_IO.In_File,
                       "FILENAME.TXT");
      Ada.Text_IO.Put_Line("2");
      Ada.Text_IO.Close(Input_File);
      Ada.Text_IO.Put_Line("3");
   end Read_And_Print_Patches;

end TestFileRead;
===========