Re: [fpc-pascal] Why in {$mode delphi} it works and in {$mode objfpc} it doesn't?
Il 16/01/23 22:23, Mattias Gaertner via fpc-pascal ha scritto: On Mon, 16 Jan 2023 22:12:52 +0100 Mattias Gaertner via fpc-pascal wrote: On Mon, 16 Jan 2023 19:50:34 +0100 Giuliano Colla via fpc-pascal wrote: I stumbled into a problem I don't understand. I'm developing a little program for an ftp client. In order to connect to the site I need the site address from the site name, and the libc gethostbyname() provides the required information. gethostbyname returns a PHostEnt type which is declared as: Btw, gethostbyname is obsolete. Applications should use getaddrinfo, getnameinfo, and gai_strerror instead. I know that it's obsolete. It's not reentrant and it is ugly. But I'm pretty sure that it will survive for a long time to come, because it provides you a check on a name *before* creating a socket. If the name is wrong (a typo, e.g.) you don't need to get rid of an useless socket, as it would happen with getaddrinfo and getnameinfo. [...] Ah, I just saw gethostbyname returns a PHostEnt and Addr is Pin_addr. Then for the first address: Addr := Pin_addr(HostEnt^.h_addr[0]); IT WORKS! But for me it's a bit obscure why in Delphi mode the right syntax is HostEnt.h_addr^ and in objfpc HostEnt.h^.h_addr[0] I can understand the first caret (Delphi puts it there implicitly) but not the rest. However thanks a lot. If gethostbyname can be a little obsolete, Delphi mode for me is much more obsolete and deprecated! Giuliano___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Why in {$mode delphi} it works and in {$mode objfpc} it doesn't?
Il 16/01/23 20:58, Marco van de Voort via fpc-pascal ha scritto: On 16-1-2023 20:56, Giuliano Colla via fpc-pascal wrote: No chance. Addr is a pointer (of type Pin_addr) but Addr := Pin_addr(HostEnt.h_addr^) works only if mode is Delphi. In objfpc it raises exactly the same error. A little bit weird, isn't it? It depends. It assumes .h_addr is compatible with pointer. Since Free Pascal is more portable, that might be a platform dependent assumption. I fail to grasp the different assumptions that the compiler makes on objfpc mode. If the typecast tells that the two types are compatible (and they are, because they're both pointers and also of the same type) it should write the one to the other without making any fuss! But I can live with it! The horrible mess they've done with gethostbyname, and the chars which are actually bytes is not so frequent, luckily! That's what happens when you don't have the "based" construct, which makes very easy to deal with those situations. Different structures can be based on the same pointer, and one "type" field, common to all structures, makes you pick up the right one. Giuliano Giuliano ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Why in {$mode delphi} it works and in {$mode objfpc} it doesn't?
On Mon, 16 Jan 2023 22:12:52 +0100
Mattias Gaertner via fpc-pascal wrote:
> On Mon, 16 Jan 2023 19:50:34 +0100
> Giuliano Colla via fpc-pascal wrote:
>
> > I stumbled into a problem I don't understand.
> >
> > I'm developing a little program for an ftp client. In order to
> > connect to the site I need the site address from the site name, and
> > the libc gethostbyname() provides the required information.
> >
> > gethostbyname returns a PHostEnt type which is declared as:
Btw, gethostbyname is obsolete. Applications should use getaddrinfo,
getnameinfo, and gai_strerror instead.
> > > THostEnt = packed record
> > > h_name: PChar; { Official name of host. }
> > > h_aliases: PPChar; { Alias list. }
> > > h_addrtype: Integer; { Host address type. }
> > > h_length: socklen_t; { Length of address. }
> > > case Byte of
> > > 0: (h_addr_list: PPChar); { List of addresses from name
> > > server. }
> > > 1: (h_addr: PPChar); { Address, for backward
> > > compatibility. }
> > > end;
> > > PHostEnt = ^THostEnt;
> > Actually the chars h_addr points to are /hlength/ bytes to be
> > interpreted as an /in_addr/
> [...]
Ah, I just saw gethostbyname returns a PHostEnt and Addr is Pin_addr.
Then for the first address:
Addr := Pin_addr(HostEnt^.h_addr[0]);
Mattias
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Re: [fpc-pascal] Why in {$mode delphi} it works and in {$mode objfpc} it doesn't?
On Mon, 16 Jan 2023 19:50:34 +0100
Giuliano Colla via fpc-pascal wrote:
> I stumbled into a problem I don't understand.
>
> I'm developing a little program for an ftp client. In order to
> connect to the site I need the site address from the site name, and
> the libc gethostbyname() provides the required information.
>
> gethostbyname returns a PHostEnt type which is declared as:
>
> > THostEnt = packed record
> > h_name: PChar; { Official name of host. }
> > h_aliases: PPChar; { Alias list. }
> > h_addrtype: Integer; { Host address type. }
> > h_length: socklen_t; { Length of address. }
> > case Byte of
> > 0: (h_addr_list: PPChar); { List of addresses from name
> > server. }
> > 1: (h_addr: PPChar); { Address, for backward
> > compatibility. }
> > end;
> > PHostEnt = ^THostEnt;
> Actually the chars h_addr points to are /hlength/ bytes to be
> interpreted as an /in_addr/
Then either
Addr := Pin_addr(HostEnt.h_addr)^;
or
Addr := Pin_addr(HostEnt.h_addr^)^;
Mattias
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Re: [fpc-pascal] Why in {$mode delphi} it works and in {$mode objfpc} it doesn't?
On 16-1-2023 20:56, Giuliano Colla via fpc-pascal wrote: No chance. Addr is a pointer (of type Pin_addr) but Addr := Pin_addr(HostEnt.h_addr^) works only if mode is Delphi. In objfpc it raises exactly the same error. A little bit weird, isn't it? It depends. It assumes .h_addr is compatible with pointer. Since Free Pascal is more portable, that might be a platform dependent assumption. ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Why in {$mode delphi} it works and in {$mode objfpc} it doesn't?
Il 16/01/23 20:32, Michael Van Canneyt ha scritto: On Mon, 16 Jan 2023, Giuliano Colla via fpc-pascal wrote: .I stumbled into a problem I don't understand. Should that not simply be Addr := Pin_addr(HostEnt.h_addr^) (if addr is a pointer) or addr:=Pin_addr(HostEnt.h_addr^)^ if Addr is an in_addr record ? Michael. No chance. Addr is a pointer (of type Pin_addr) but Addr := Pin_addr(HostEnt.h_addr^) works only if mode is Delphi. In objfpc it raises exactly the same error. A little bit weird, isn't it? Giuliano ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Why in {$mode delphi} it works and in {$mode objfpc} it doesn't?
On Mon, 16 Jan 2023, Giuliano Colla via fpc-pascal wrote:
I stumbled into a problem I don't understand.
I'm developing a little program for an ftp client. In order to connect to the
site I need the site address from the site name, and the libc gethostbyname()
provides the required information.
gethostbyname returns a PHostEnt type which is declared as:
THostEnt = packed record
h_name: PChar; { Official name of host. }
h_aliases: PPChar; { Alias list. }
h_addrtype: Integer; { Host address type. }
h_length: socklen_t; { Length of address. }
case Byte of
0: (h_addr_list: PPChar); { List of addresses from name server.
}
1: (h_addr: PPChar); { Address, for backward compatibility.
}
end;
PHostEnt = ^THostEnt;
Actually the chars h_addr points to are /hlength/ bytes to be interpreted as
an /in_addr/
In order to recover h_addr I have a line which works perfectly in Delphi mode
(inherited from an old Kylix app):
Addr := Pin_addr(HostEnt.h_addr^);
I believed that in objfpc mode it was sufficient to change it in
Addr := @(Pin_addr(HostEnt.h_addr^));
or in
Addr := Pin_addr(@HostEnt.h_addr^);
Should that not simply be
Addr := Pin_addr(HostEnt.h_addr^)
(if addr is a pointer)
or
addr:=Pin_addr(HostEnt.h_addr^)^
if Addr is an in_addr record ?
Michael.___
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[fpc-pascal] Why in {$mode delphi} it works and in {$mode objfpc} it doesn't?
I stumbled into a problem I don't understand.
I'm developing a little program for an ftp client. In order to connect
to the site I need the site address from the site name, and the libc
gethostbyname() provides the required information.
gethostbyname returns a PHostEnt type which is declared as:
THostEnt = packed record
h_name: PChar; { Official name of host. }
h_aliases: PPChar; { Alias list. }
h_addrtype: Integer; { Host address type. }
h_length: socklen_t; { Length of address. }
case Byte of
0: (h_addr_list: PPChar); { List of addresses from name
server. }
1: (h_addr: PPChar); { Address, for backward
compatibility. }
end;
PHostEnt = ^THostEnt;
Actually the chars h_addr points to are /hlength/ bytes to be
interpreted as an /in_addr/
In order to recover h_addr I have a line which works perfectly in Delphi
mode (inherited from an old Kylix app):
Addr := Pin_addr(HostEnt.h_addr^);
I believed that in objfpc mode it was sufficient to change it in
Addr := @(Pin_addr(HostEnt.h_addr^));
or in
Addr := Pin_addr(@HostEnt.h_addr^);
but such is not the case. In both cases it flags the line with the same
error, i.e.:
Error: illegal qualifier
Hint: may be pointer dereference is missing
Fatal: Syntax error, ")" expected but "identifier H_ADDR" found
What I'm missing? How should i write that line of code to make it work
in objfpc mode?
Thanks,
Giuliano
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