[fpc-devel] THandle and 64bit platforms

[Tomas Hajny]

Date sent:      	Mon, 20 Dec 2004 21:02:04 +0100
To:             	"FPC developers' list" <fpc-devel at lists.freepascal.org>
From:           	Marc Weustink <marc at dommelstein.net>
Subject:        	RE: [fpc-devel] THandle and 64bit platforms
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> > > >>>>File descriptors are still 32bit on x86_64, therefor
> > > >>>>Thandle=32bit.
> > > >>>
> > > >>> A THandle is more than a file descriptor alone.
> > > >>> Since the LCL is VCL compatible and thus MS biassed, there are
> > > >>> more THandles than filedescriptors alone. To keep code
> > > >>> compatible and portable, I need a 64 bit THandle on 64 bit
> > > >>> platforms. (on win64 a handle is also 64bit). Or would you
> > > >>> suggest to use HANDLE for a 64bit handle and THandle for 32bit
> > > >>> ?
> > > >>
> > > >>THandle is platform dependent. On win64 THandle=QWord.
> > > >>
> > > >>Currently Thandle=longint for unix, but Thandle=DWord for win32.
> > > >
> > > > Yes, I am aware of that, my question however is is how to get
> > > > things working.
> > > >
> > > > In the LCL a THandle is used everywhere and in most cases it
> > > > represents a pointer. It is also part of the emulated message
> > > > records. All members of it are defined as PtrInt. On placed
> > > > where a handle is iused, it should map on a PtrInt.
 .
 .
> That would be my choice also.
> For me a THandle is a generic abstract identifier, which can identify
> a file, a window, a process, a thread, a event, a bitmap, a pen, a
> brush, a region, a font, a DC, a whatever_I_forgot_more THandle is
> used as basetype for all these types of handles. And personally I
> think it is a bit limitted to use it only for a filehandle.

Well, whereas I agree that handles can be more than file descriptors, 
I don't see any connection between this fact and requirement to have 
handles of the same size as pointers (although I understand your 
reason)... In addition, having handles incompatible to file 
descriptors would break Delphi compatibility as well. Proper 
emulation of Windows handles would IMHO probably really require some 
kind of mapping between handles and pointers as mentioned in one of 
your previous e-mails.

Tomas