In go32v2 i got a problem with case statement.
With compiler 1.0.10 is this without errors:

const kbDown = $5000;
      kbUp   = $4800;
var ch : char;
begin
  ch:=ReadKey;
  case ord(ch) of
    Hi(kbDown): writeln('kbDown');
    Hi(kbUp)  : writeln('kbUp');
  end;
end.

New FPC compiler 1.9.3 produced error 'duplicate case label'.

With these commands i found that function HI produced 0 for both constants.

  writeln(HexStr(Hi(kbDown),2));
  writeln(HexStr(Hi(kbUp),2));

OK i changed definition of kbDown and kbUp to

const kbDown : word = $5000;
      kbUp   : word = $4800;

and now Hi(kbDown) return $50 etc. but with compilation i got another error 'Constant Expression expected'.

I know what this is but i don't understand why.

Maybe somebody help me ?

This definition 'const kbDown = $5000;' produced word or logint or ... ?

Lubomir Cabla

Delphi (5 at least) enforces case items to be constants, ie. fixed at compile time..... this looks to be the thing that's changed in the compiler's default mode. Maybe another mode supports extended case functionality?

Anyway, define a const for $50 and $48 and use them... aren't these values fixed at compile time anyway ?

Thanks.

Yes, you're right but i'm using this constants for backward compatibility with Borland Pascal.

The problem is in declarations of constant:

const xxx = $4400;
         yyy = $11;

SizeOf(xxx) = 2 in FPC 1.0.10
4 in FPC 1.9.x
SizeOf(yyy) = 1 in FPC 1.0.10
4 in FPC 1.9.x

Constants xxx and yyy are ordinal types, but i don't know which count of bytes they got.

Maybe now are all constants defined like longword (dword), but in PDF doc for 1.9.2
i can not find this.

Lubomir Cabla

From:
To:
Subject: RE: [fpc-pascal]Problem with CASE statement Date sent: Wed, 24 Mar 2004 08:01:04 +0100

Hi (word (xxx)) should work everywhere if you need to specify the size explicitely. You're right that it should be documented, of course.

Tomas

Hi,

yes i know this re-typing word(xxx), it is OK.

Second - new FPC v1.9.x for statement

var p:pointer
p:=Ptr(a,b);

shows error "Incompatible types: got "FarPointer" expected "Pointer"".

I found i can declare var p:farpointer;
but i did not found any description for this type of pointer how can i use it.

Lubomir Cabla

Fixed

Farpointer is to support mem[] and ptr(seg,offset)^ to access the real mode memory. The type is incompatible with Pointer so you can't accidently use Move() etc. You need the special functions from go32 to access the real mode memory.

Many thanks for your explanation.

Hello,

It seems that the syntax and semantics of this function changed with later FPC-versions to something actually useful... ;-)

A "Farpointer" is a pointer consisting of a 16 bit selector and 32 bit offset, while in BP the Ptr() function expected a 16bit/16bit segment:offset.
This is due to different memory models in 32 bit protected mode of FPC and 16 bit real mode in BP/TP. There is no fully compatible automatic way to handle these problems.

In short, you usually don't ever need the Ptr() - function in FPC because all memory is addressed linearly through a single 32 bit address, just use "p := @avariable" if you want to create a pointer to some memory area. It was sometimes required in BP/TP because of memory segmentation in BP programs.

Otoh if you want to access specific memory areas in the real mode memory area (lower 1MB of memory) you need to do some sort of translation. See the go32 - documentation for further details (there is some information about the farpointer stuff as well iirc) if you just want to port your TP/BP DOS application to the go32v2 target.
For the others such a way of accessing memory will not be allowed by the OS anyway (or is limited) and is impossible to do without lots of application and OS specific code.

Eventually this will give you a farpointer to the DOS memory location you want to access:

uses go32;
var p : farpointer;
// this syntax is just a guess.
p := Ptr(getfs(), a shl 4 + b);

getfs() returns a selector which by default describes the DOS memory area. Note that while constructing a pointer to this area might work in all cases, any NT-based OS might prevent access. At least it will be slow. Don't even consider using this on e.g. *nix systems.

Regards,
Thomas

Do you have a HOME environment variable set? It says it can't find your home directory where login information is stored.

Vincent.

Hi there,

I haven't cvs'd in a number of months, and it is no longer working. I have a little ms-dos batch file that enters the long command for me, so it's not as if my configuration or command or path has changed. I keep getting this error:

CVS.EXE [update aborted]: could not find out home directory

Perhaps this is just a fluke of the night, or perhaps something somewhere has changed? I see that the instructions on the web have not changed in a long, long time!

if it's relevant...

cvs -d -z 3 update -Pd fpc/compiler fpc/rtl fpc/Makefile fpc/Makefile.fpc

(while I'm on the subject, correct me if I'm wrong... this ought to be the minimum to get the compiler + rtl working, compiling from 1.0.10, right?)

Thanks,
David

This is a local error. Seems like the HOME environment variable is not set or pointing to a wrong directory ?

Perhaps this is just a fluke of the night, or perhaps something somewhere has changed? I see that the instructions on the web have not changed in a long, long time!

Because they are still correct. Nothing has changed on the server.

Yes.

Michael.