Re: [fpc-pascal] Abstract classes ignored
> On Apr 18, 2021, at 11:28 PM, Sven Barth wrote: > > Nowadays: backwards compatibility. backwards compatibility strikes again. :) Regards, Ryan Joseph ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Abstract classes ignored
Am 18.04.2021 um 19:58 schrieb Ryan Joseph via fpc-pascal: On Apr 18, 2021, at 5:00 AM, Sven Barth wrote: As I have said: Delphi compatibility. This would have been a good candidate to put behind the delphi mode switch but I'm sure there is a reason for this also. Nowadays: backwards compatibility. Regards, Sven ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Abstract classes ignored
Graeme Geldenhuys via fpc-pascal schrieb am So., 18. Apr. 2021, 17:54: > > On 18/04/2021 11:31 am, C Western via fpc-pascal wrote: > > but there are also case where it never makes sense to > > implement them and calling them indicates a logical error elsewhere in > > the code. > > So do the logical thing... Throw an exception! Don't promote a faulty > compiler. Fix your code instead. > Calling an abstract method will already result in an EAbstractError to be thrown. Regards, Sven > ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Abstract classes ignored
Jonas Maebe via fpc-pascal schrieb am
So., 18. Apr. 2021, 21:19:
> On 18/04/2021 18:08, Jonas Maebe via fpc-pascal wrote:
> > In this case, you
> > can easily make it an error yourself with {$warn 4046 error}.
>
> Correction: that's make it an error to construct a classes that contain
> abstract methods. For abstract classes, it's {$warn 4122 error}
>
Or as I had written already: {$WARN CONSTRUCTING_ABSTRACT ERROR}. This will
switch both warnings to error.
Regards,
Sven
>
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Re: [fpc-pascal] Abstract classes ignored
On 18/04/2021 18:08, Jonas Maebe via fpc-pascal wrote:
> In this case, you
> can easily make it an error yourself with {$warn 4046 error}.
Correction: that's make it an error to construct a classes that contain
abstract methods. For abstract classes, it's {$warn 4122 error}
Jonas
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Re: [fpc-pascal] Abstract classes ignored
On Sun, Apr 18, 2021 at 7:56 PM Travis Siegel via fpc-pascal wrote: >... but the last time I asked them > about pricing, they told me it'd cost $1000 for just delphi 7, and that > only costed $995 when it first came out, nearly 20 years ago. Wow! Long time ago, I bought Delphi2 (it was bundled with Delphi 1, and that was the one I needed, since I was on Win 3.10) for about ƒ200. (€1.00 = ƒ2.20). It came with a full manual (on paper that is). Those were the days -- Bart ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Abstract classes ignored
> On Apr 18, 2021, at 5:00 AM, Sven Barth wrote: > > As I have said: Delphi compatibility. This would have been a good candidate to put behind the delphi mode switch but I'm sure there is a reason for this also. Regards, Ryan Joseph ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Abstract classes ignored
On 4/18/2021 11:55 AM, Graeme Geldenhuys via fpc-pascal wrote: On 17/04/2021 10:09 pm, Sven Barth via fpc-pascal wrote: but Delphi compatbility is more important here, thus the default is a warning and not an error. How is this beneficial? The compiler should help the developer, but here it was decided that it's beneficial for the program to crash at runtime, because follow the broken Delphi compiler is more important! *shrug* Such decisions really make me worry about the future of FPC. It ends up being NO better than Delphi, so why bother using FPC then. Stick to Delphi instead. If you're willing to pay for me to obtain a delphi license, then I'd happily switch. Seeing as how they charge over a thousand dollars even during their supposed sales, I have no interest in spending that kind of money for an environment that FPC offers for free. That means I don't have to spend my limited income on a license for a program I use a few times a year. Admittedly, part of the reason I use it so rarely is because I really need to dig into it's gui and tcp capabilities (I program from the ocmmand prompt, but being able to generate gui screens on the fly would be nice). I know Delphi can do this, but the last time I asked them about pricing, they told me it'd cost $1000 for just delphi 7, and that only costed $995 when it first came out, nearly 20 years ago. I refuse to support that kind of price gouging, even if I could afford it. But, as I said, if you're willing to foot the bill, I'd happily use it, as it does indeed have (some) advantages. ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Abstract classes ignored
On 18/04/2021 17:55, Graeme Geldenhuys via fpc-pascal wrote:
> On 17/04/2021 10:09 pm, Sven Barth via fpc-pascal wrote:
>> but Delphi compatbility is more
>> important here, thus the default is a warning and not an error.
>
> How is this beneficial? The compiler should help the developer,
People who want to compile code in both FPC and Delphi are developers
too. People who want to use their knowledge of Delphi to program in FPC
are developers too.
You can never make everyone happy, and sometimes we go for
incompatibility by default, and sometimes we don't. In this case, you
can easily make it an error yourself with {$warn 4046 error}.
> Such decisions really make me worry about the future of FPC. It ends up
> being NO better than Delphi, so why bother using FPC then. Stick to
> Delphi instead.
It's not like this is a new policy that you just discovered, so please
stop already with the flamebait drama about how this makes you worry
about the future of FPC.
Jonas
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Re: [fpc-pascal] Abstract classes ignored
On 17/04/2021 10:09 pm, Sven Barth via fpc-pascal wrote: > but Delphi compatbility is more > important here, thus the default is a warning and not an error. How is this beneficial? The compiler should help the developer, but here it was decided that it's beneficial for the program to crash at runtime, because follow the broken Delphi compiler is more important! *shrug* Such decisions really make me worry about the future of FPC. It ends up being NO better than Delphi, so why bother using FPC then. Stick to Delphi instead. Regards, Graeme ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Abstract classes ignored
On 18/04/2021 11:31 am, C Western via fpc-pascal wrote: > but there are also case where it never makes sense to > implement them and calling them indicates a logical error elsewhere in > the code. So do the logical thing... Throw an exception! Don't promote a faulty compiler. Fix your code instead. Regards, Graeme ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Abstract classes ignored
Am 18.04.2021 um 04:34 schrieb Ryan Joseph via fpc-pascal: On Apr 17, 2021, at 3:09 PM, Sven Barth wrote: The compiler will generate a warning in case you instantiate a class that is abstract or has abstract methods. You can escalate these warnings to errors if you need: It's probably not practical to put that warning into all potential files but a warning is still probably good enough as a reminder. It's curious though why it's not an error by default, because if the class is abstract and you instantiate it and try to use it things are going to fail anyways so why does the compiler allow it in the first place? As I have said: Delphi compatibility. Regards, Sven ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Abstract classes ignored
On 18/04/2021 03:34, Ryan Joseph via fpc-pascal wrote: On Apr 17, 2021, at 3:09 PM, Sven Barth wrote: The compiler will generate a warning in case you instantiate a class that is abstract or has abstract methods. You can escalate these warnings to errors if you need: It's probably not practical to put that warning into all potential files but a warning is still probably good enough as a reminder. It's curious though why it's not an error by default, because if the class is abstract and you instantiate it and try to use it things are going to fail anyways so why does the compiler allow it in the first place? Regards, Ryan Joseph ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal My own code will have cases where I have only implemented some of the abstract methods for some classes, in principle because the code is incomplete, but there are also case where it never makes sense to implement them and calling them indicates a logical error elsewhere in the code. Colin ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Abstract classes ignored
> On Apr 17, 2021, at 3:09 PM, Sven Barth wrote: > > The compiler will generate a warning in case you instantiate a class that is > abstract or has abstract methods. You can escalate these warnings to errors > if you need: It's probably not practical to put that warning into all potential files but a warning is still probably good enough as a reminder. It's curious though why it's not an error by default, because if the class is abstract and you instantiate it and try to use it things are going to fail anyways so why does the compiler allow it in the first place? Regards, Ryan Joseph ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Abstract classes ignored
Am 17.04.2021 um 20:30 schrieb Ryan Joseph via fpc-pascal:
From the documentation: "An abstract class is a class that cannot be instantiated
directly. Instead, a descendent class must always be instantiated. However, for Delphi
compatibility, the compiler ignores this directive."
Why does this get ignored and what does this have to do with Delphi? I
personally would like for this to actually work and give a compiler error if
you instantiate the abstract class.
The compiler will generate a warning in case you instantiate a class
that is abstract or has abstract methods. You can escalate these
warnings to errors if you need:
=== code begin ===
program tabstract;
{$MODE OBJFPC}
{$WARN CONSTRUCTING_ABSTRACT ERROR}
type
TAbstract1 = class abstract
end;
TAbstract2 = class
procedure Test; virtual; abstract;
end;
var
a1: TAbstract1;
a2: TAbstract2;
begin
a1 := TAbstract1.Create;
a2 := TAbstract2.Create;
end.
=== code end ===
This will generate two (different) errors.
With this we're allowing more than Delphi does (which warns in the
second case, but the warning can not be escalated to error and does not
warn for the first case at all), but Delphi compatbility is more
important here, thus the default is a warning and not an error. This
will not be changed.
Regards,
Sven
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[fpc-pascal] Abstract classes ignored
From the documentation: "An abstract class is a class that cannot be instantiated directly. Instead, a descendent class must always be instantiated. However, for Delphi compatibility, the compiler ignores this directive." Why does this get ignored and what does this have to do with Delphi? I personally would like for this to actually work and give a compiler error if you instantiate the abstract class. Regards, Ryan Joseph ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] abstract classes
From: Howard Page-Clark h...@talktalk.net
To: FPC users list fpc-pascal@lists.freepascal.org
Sent: Sunday, January 20, 2013 8:37 PM
Subject: [fpc-pascal] abstract classes
FPC allows the Delphi-compatible class abstract syntax, but does not seem to
prevent instantiation of such a class.
The following code compiles and runs satisfactorily (FPC version 2.6.0)
Does trunk prevent this compiling?
program Project1;
{$mode objfpc}{$H+}
type
TAbstractClass = class abstract
class function GetID: integer; static;
end;
class function TAbstractClass.GetID: integer;
begin
Result:= 10;
end;
var
ac: TAbstractClass;
begin
ac:= TAbstractClass.Create;
WriteLn(ac.GetID);
ReadLn;
ac.Free;
end.
As far as I remember Delphi has the same behavior.
Leonardo M. Ramé
http://leonardorame.blogspot.com
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Re: [fpc-pascal] abstract classes
On 01/21/13 22:28, Leonardo M. Ramé wrote: As far as I remember Delphi has the same behavior. As I said in the other thread - it is a bug! Completely defeats the design principal of what abstract class or method means. FPC should raise an error. I don't care what Delphi does - it's wrong. Regards, - Graeme - ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] abstract classes
On Mon, Jan 21, 2013 at 10:59 PM, Graeme Geldenhuys gra...@geldenhuys.co.uk wrote: As I said in the other thread - it is a bug! Completely defeats the design principal of what abstract class or method means. FPC should raise an error. I don't care what Delphi does - it's wrong. I agree, it's awkward to just let the compiling proceed with code that can cause avoidable errors at runtime. What about letting this behavior as is ONLY for the delphi mode and abort compiling for objfpc ? ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
[fpc-pascal] abstract classes
FPC allows the Delphi-compatible class abstract syntax, but does not
seem to prevent instantiation of such a class.
The following code compiles and runs satisfactorily (FPC version 2.6.0)
Does trunk prevent this compiling?
program Project1;
{$mode objfpc}{$H+}
type
TAbstractClass = class abstract
class function GetID: integer; static;
end;
class function TAbstractClass.GetID: integer;
begin
Result:= 10;
end;
var
ac: TAbstractClass;
begin
ac:= TAbstractClass.Create;
WriteLn(ac.GetID);
ReadLn;
ac.Free;
end.
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Re: [fpc-pascal] abstract classes
On 21 Jan 2013, at 00:37, Howard Page-Clark wrote: FPC allows the Delphi-compatible class abstract syntax, but does not seem to prevent instantiation of such a class. The following code compiles and runs satisfactorily (FPC version 2.6.0) Does trunk prevent this compiling? No. Also see http://www.mail-archive.com/fpc-pascal@lists.freepascal.org/msg31040.html Jonas___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
