[fpc-pascal] Free Pascal bindings for EyeLink C code (with a god-cast)
Rafael Picanço
cpicanco42 at gmail.com
Wed Jun 14 20:59:41 CEST 2023
Hi Marco,
I am trying to follow your advice and use units instead:
const
EXTERNAL_DEV_NONE : TGetExButtonStatesFunction = Pointer(0);
However I am receiving an error:
Error: Incompatible types: got "Pointer" expected "<procedure variable type
of function(PCCDBS):LongInt;CDecl>"
Please, can you shed some light on this?
Best,
R
On Wed, Jun 14, 2023 at 7:00 AM <fpc-pascal-request at lists.freepascal.org>
wrote:
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> Today's Topics:
>
> 1. Re: fpc isn't optimised for tail recursion, is it?
> (Jean SUZINEAU)
> 2. Re: Free Pascal bindings for EyeLink C code (with a
> god-cast) (Rafael Pican?o)
> 3. Re: Free Pascal bindings for EyeLink C code (with a
> god-cast) (Marco van de Voort)
> 4. Re: Non-initialized member access warning (Hairy Pixels)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 13 Jun 2023 15:25:59 +0200
> From: Jean SUZINEAU <jean.suzineau at wanadoo.fr>
> To: fpc-pascal at lists.freepascal.org
> Subject: Re: [fpc-pascal] fpc isn't optimised for tail recursion, is
> it?
> Message-ID: <310a7c2b-a874-b5d3-f80f-f492903580d7 at wanadoo.fr>
> Content-Type: text/plain; charset="utf-8"; Format="flowed"
>
> Le 12/06/2023 ? 19:05, Steve Litt via fpc-pascal a ?crit?:
> > Busted! I used Pascal 1984-1993
> So I guess you are not familiar too with the "Result" variable which
> appeared with Delphi 1 in 1995 if I remember correctly.
>
> nextt:= num;
>
> can be written to as :
>
> Result:= num;
>
> https://www.freepascal.org/docs-html/ref/refse94.html
>
> I prefer Result because it reduces risks of confusion with recursive call
> and you can eventually take the address of Result with @Result (where
> @nextt would take the address of the function nextt),
> pass it by reference to another function ( e.g. FillChar( Result,
> SizeOf(Result), 0); ) ,
> it behaves like a normal variable.
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> ------------------------------
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> Message: 2
> Date: Tue, 13 Jun 2023 10:38:22 -0300
> From: Rafael Pican?o <cpicanco42 at gmail.com>
> To: fpc-pascal at lists.freepascal.org
> Subject: Re: [fpc-pascal] Free Pascal bindings for EyeLink C code
> (with a god-cast)
> Message-ID:
> <CAGpuCi5mjRLeCnMY=
> mhrBM9kjf7r+BRv6yRr3YDXT8njuHT2Cw at mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> Thank you Marco, I am elaborating on top of your suggestions.
>
> > The problem is that the logical solution, making it a macro, doesn't
> work, as macro definitions don't export through USES clauses.
>
> I think that pre-processor constants with $I would be a valid alternative
> for using the best solution. For example:
>
> // constants.pp
> ____
> {$MACRO ON}
> {$ifndef EXTERNAL_DEV_NONE}
> {$DEFINE EXTERNAL_DEV_NONE := TGetExButtonStatesFunction(Pointer(0))}
> {$endif}
> {$ifndef EXTERNAL_DEV_CEDRUS}
> {$DEFINE EXTERNAL_DEV_CEDRUS := TGetExButtonStatesFunction(Pointer(1))}
> {$endif}
> {$ifndef EXTERNAL_DEV_SYS_KEYBOARD}
> {$DEFINE EXTERNAL_DEV_SYS_KEYBOARD :=
> TGetExButtonStatesFunction(Pointer(2))}
> {$endif}
> ____
>
> program godcastsucks;
>
> {$I constants}
>
> type
>
> PCCDBS = ^TCCDBS;
> TCCDBS = record
> userdata: Pointer;
> buttons: array[0..255] of AnsiChar;
> internal: Pointer;
> end;
>
> TGetExButtonStatesFunction = function (accdbs: PCCDBS): Int32; cdecl;
>
> function enable_external_calibration_device(
> buttonStatesfcn: Pointer {other arguments removed for simplicity}):
> Int32; cdecl;
> var
> Statesfcn : TGetExButtonStatesFunction;
> begin
> Result := Int32(TGetExButtonStatesFunction(@buttonStatesfcn^));
> case Result of
> 0 : { do nothing };
> else
> begin
> Statesfcn := TGetExButtonStatesFunction(buttonStatesfcn);
> Statesfcn(nil);
> Result := -1;
> end;
> end;
> end;
>
> function ExButtonStatesFunction(accdbs: PCCDBS): Int32; cdecl;
> begin
> WriteLn('God casts sucks');
> end;
>
> begin
> WriteLn(enable_external_calibration_device(EXTERNAL_DEV_NONE));
> WriteLn(enable_external_calibration_device(@ExButtonStatesFunction));
> ReadLn;
> end.
> ____
>
> > Note that an alternative for this macro exists since FPC 3.2.0:
>
> Thank you for the reference!
>
> On Tue, Jun 13, 2023 at 7:00?AM <fpc-pascal-request at lists.freepascal.org>
> wrote:
>
> > Send fpc-pascal mailing list submissions to
> > fpc-pascal at lists.freepascal.org
> >
> > To subscribe or unsubscribe via the World Wide Web, visit
> > https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
> > or, via email, send a message with subject or body 'help' to
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> >
> > You can reach the person managing the list at
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> >
> > When replying, please edit your Subject line so it is more specific
> > than "Re: Contents of fpc-pascal digest..."
> >
> >
> > Today's Topics:
> >
> > 1. Re: Free Pascal bindings for EyeLink C code (with a
> > god-cast) (Marco van de Voort)
> >
> >
> > ----------------------------------------------------------------------
> >
> > Message: 1
> > Date: Tue, 13 Jun 2023 11:25:13 +0200
> > From: Marco van de Voort <fpc at pascalprogramming.org>
> > To: fpc-pascal at lists.freepascal.org
> > Subject: Re: [fpc-pascal] Free Pascal bindings for EyeLink C code
> > (with a god-cast)
> > Message-ID:
> > <5a5a8eac-e91d-d9d7-4131-d7301ec3c4d3 at pascalprogramming.org>
> > Content-Type: text/plain; charset=UTF-8; format=flowed
> >
> >
> > On 13-6-2023 05:19, Rafael Pican?o via fpc-pascal wrote:
> > > (1) I have no idea on how to translate these god-casts, eg.,
> > > ((getExButtonStates)0), to free pascal. Right now, I think that even
> > > if I don't really need them, I just want?to understand and learn
> > > in?the?process.
> >
> > The problem is that the logical solution, making it a macro, doesn't
> > work, as macro definitions don't export through USES clauses.
> >
> > Defining it a proper constant would be the best solution, but FPC
> > doesn't like it :
> >
> > const
> >
> > ?EXTERNAL_DEV_NONE = TGetExButtonStatesFunction(pointer(0));
> >
> > so the next best is turning it into a type constant at the expense of
> > sizeof(pointer) bytes in the binary:
> >
> > const
> >
> > ? EXTERNAL_DEV_NONE : TGetExButtonStatesFunction= pointer(0);
> >
> > etc etc.
> >
> > >
> > > (2) So, the whole point here is?binding the
> > > "enable_external_calibration_device" function. It expects a
> > > "getExButtonStates buttonStatesfcn". Can you check if my current
> > > binding is right?
> > >
> > A purist would say it needs to be "ansichar" rather than char (because
> > in future unicode modes char could be 2-byte, for the rest it seems ok.
> >
> > > (3) I am using the?ELCALLTYPE?macro just because?they were?using them
> > > too,?I am assuming backward compatibility. But I am not sure if I
> > > really need them. EyeLink code depends on custom SDL2 headers and I
> > > am?running SDL2 Free Pascal related stuff just fine (and it has cdecl
> > > in everything). What do you think about that? For reference, this is
> > > the macro:
> > >
> > You must match the calling convention of the implementation. Some
> > functions have target dependent calling conventions, some non native
> > libraries force cdecl even on Windows. (where stdcall or fastcall is
> > more conventional)
> >
> > Note that an alternative for this macro exists since FPC 3.2.0:
> >
> >
> >
> https://wiki.freepascal.org/FPC_New_Features_3.2.0#Support_for_WinAPI_directive
> >
> > Even though the naming is not "elegant" for crossplatform usage.
> >
> >
> > ------------------------------
> >
> > Subject: Digest Footer
> >
> > _______________________________________________
> > fpc-pascal maillist - fpc-pascal at lists.freepascal.org
> > https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
> >
> >
> > ------------------------------
> >
> > End of fpc-pascal Digest, Vol 228, Issue 14
> > *******************************************
> >
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> ------------------------------
>
> Message: 3
> Date: Tue, 13 Jun 2023 15:48:36 +0200
> From: Marco van de Voort <fpc at pascalprogramming.org>
> To: fpc-pascal at lists.freepascal.org
> Subject: Re: [fpc-pascal] Free Pascal bindings for EyeLink C code
> (with a god-cast)
> Message-ID:
> <7e225875-c784-019a-1091-a89f612ef423 at pascalprogramming.org>
> Content-Type: text/plain; charset=UTF-8; format=flowed
>
>
> On 13-6-2023 15:38, Rafael Pican?o via fpc-pascal wrote:
> > Thank you Marco, I am elaborating on top of your suggestions.
> >
> > > The problem is that the logical solution, making it a macro, doesn't
> > work, as macro definitions don't export through USES clauses.
> >
> > I think that pre-processor constants with $I would be a valid
> > alternative for using the best solution. For example:
> >
> A matter of taste. I would have as less macros as possible. Moreover the
> typed const doesn't require including additional files at the usage
> site, so IMHO it is objectively a better solution
>
>
> ------------------------------
>
> Message: 4
> Date: Wed, 14 Jun 2023 13:50:34 +0700
> From: Hairy Pixels <genericptr at gmail.com>
> To: Sven Barth <pascaldragon at googlemail.com>
> Cc: FPC-Pascal users discussions <fpc-pascal at lists.freepascal.org>
> Subject: Re: [fpc-pascal] Non-initialized member access warning
> Message-ID: <86575BA9-8FE9-4216-BCA0-94991010FA71 at gmail.com>
> Content-Type: text/plain; charset=us-ascii
>
>
>
> > On Jun 8, 2023, at 6:01 PM, Sven Barth <pascaldragon at googlemail.com>
> wrote:
> >
> > Please report a bug with a complete example.
>
> Better late than never :)
>
> https://gitlab.com/freepascal.org/fpc/source/-/issues/40321
>
> Regards,
> Ryan Joseph
>
>
>
> ------------------------------
>
> Subject: Digest Footer
>
> _______________________________________________
> fpc-pascal maillist - fpc-pascal at lists.freepascal.org
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>
> ------------------------------
>
> End of fpc-pascal Digest, Vol 228, Issue 15
> *******************************************
>
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