How a multiplatform code works?

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Teehee

Joined: 05 Aug 2009
Posts: 570
Location: Brazil

Teehee 27 Jan 2010, 15:07

I'd like to know how my programs may run in Windows and Linux (for example).

Lets figure out a simple program which show a MessageBox.

How my code must be to show it in both platforms?

_________________
Sorry if bad english.

27 Jan 2010, 15:07

edfed

Joined: 20 Feb 2006
Posts: 4324
Location: Now

edfed 27 Jan 2010, 15:40

your code will be layered.
the application layer
and the interface layer
interface layer is the one connected to OS.

27 Jan 2010, 15:40

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 19869
Location: In your JS exploiting you and your system

revolution 27 Jan 2010, 15:41

Teehee: You have to know the system/OS GUI interface to be able to show things like MessageBox.

There are some cross-platform libraries that attempt to make this easier, e.g. QT is one such library. There are others also.

27 Jan 2010, 15:41

Teehee

Joined: 05 Aug 2009
Posts: 570
Location: Brazil

Teehee 27 Jan 2010, 16:05

its something like:

Code:

push 0
push 0
push text
push 0
call [MessageBox]

MessageBox:
  if (win)
    invoke Messagebox,etc
  else
    invoke LinuxMB,etc
ret

27 Jan 2010, 16:05

Borsuc

Joined: 29 Dec 2005
Posts: 2465
Location: Bucharest, Romania

Borsuc 27 Jan 2010, 17:13

That's the Windows API, which would work under Linux only if Wine is installed.

27 Jan 2010, 17:13

LocoDelAssembly
Your code has a bug

Joined: 06 May 2005
Posts: 4624
Location: Argentina

LocoDelAssembly 27 Jan 2010, 17:28

Borsuc, I think you missed the conditional assembly part (although he should have used "call" without square brackets).

27 Jan 2010, 17:28

f0dder

Joined: 19 Feb 2004
Posts: 3175
Location: Denmark

f0dder 28 Jan 2010, 00:05

Teehee: conditional assembly would work, but it'd be a maintenance nightmare - you'll need to write an OS abstraction layer if you plan on getting anything done, and only use that abstraction layer from your client code. And then you have the wonderful task of implementing the abstraction layer for each OS...

If you only need simple stuff (console mode apps, file handling, memory) then it's a sort of manageable task, but add in GUI and support for more complex features... well, good luck.

28 Jan 2010, 00:05

DOS386

Joined: 08 Dec 2006
Posts: 1898

DOS386 28 Jan 2010, 06:25

Teehee wrote:

I'd like to know how my programs may run in Windows and Linux (for example).

Impossible. You can mix Win32 with DOS, but NOT Win32 with Linux: Linux requires "?ELF" Sigi, while Windows needs "MZ" - one file can't have both.

28 Jan 2010, 06:25

LocoDelAssembly
Your code has a bug

Joined: 06 May 2005
Posts: 4624
Location: Argentina

LocoDelAssembly 28 Jan 2010, 08:15

Actually, since you mentioned Win32, you could write a COM with embedded ELF and then, when the binary is running under ntvdm you would construct a temporary PE file at run-time and then execute it and when running on Linux you would do nothing as it is already executing in 32-bit mode (I think someone in this forum did that or posted something about it long ago).

28 Jan 2010, 08:15

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 19869
Location: In your JS exploiting you and your system

revolution 28 Jan 2010, 08:25

LocoDelAssembly wrote:

Actually, since you mentioned Win32, you could write a COM ..., when the binary is running under ntvdm you would construct a temporary PE file at run-time and then execute it ...

Can a DOS program tell Windows to run a PE file? What is the DOS call for that function?

28 Jan 2010, 08:25

baldr

Joined: 19 Mar 2008
Posts: 1651

baldr 28 Jan 2010, 11:02

revolution,

Yes, it can (plain int 21/ax 4B00). DOSONLY from CONFIG.NT (or PIF advanced setting for Win9x) selects whether MZ or PE will be run.

28 Jan 2010, 11:02

ManOfSteel

Joined: 02 Feb 2005
Posts: 1154

ManOfSteel 28 Jan 2010, 12:07

@DOS386

I think he meant it to be assembled as one or the other depending on the target system. Something like:

Code:

SYSTEM equ 0  ; 0 = ELF (don't forget to link the
            ; object file with the appropriate libs)
;SYSTEM equ 1   ; 1 = PE


match = 0,SYSTEM
{
format ELF
public main
}
match = 1,SYSTEM
{
format PE GUI 4.0
entry main
}


main:
       ret

28 Jan 2010, 12:07

ManOfSteel

Joined: 02 Feb 2005
Posts: 1154

ManOfSteel 28 Jan 2010, 12:18

@Teehee

The best way IMO is, like revolution said, to use cross-platform toolkits like GTK+ and Qt, along with code like the above for conditional inclusion of "headers".

Other than that, you can try edfed's method, IOW something like fasm, with system-independent code inside .inc files (e.g. %FASMDIR%/SOURCE/*) and system-dependent UI and API inside the main .asm file of every platform (e.g. %FASMDIR%/SOURCE/LIBC/FASM.ASM, %FASMDIR%/SOURCE/DOS/FASM.ASM).

28 Jan 2010, 12:18

Borsuc

Joined: 29 Dec 2005
Posts: 2465
Location: Bucharest, Romania

Borsuc 28 Jan 2010, 17:33

LocoDelAssembly wrote:

Borsuc, I think you missed the conditional assembly part (although he should have used "call" without square brackets).

But the parameters aren't the same... plus most functions have no equivalent, since the GUI APIs are different.

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Previously known as The_Grey_Beast

28 Jan 2010, 17:33

LocoDelAssembly
Your code has a bug

Joined: 06 May 2005
Posts: 4624
Location: Argentina

LocoDelAssembly 31 Jan 2010, 03:29

Finally, I found it: http://board.flatassembler.net/topic.php?t=5625

The part that can run in DOS/Linux is in this link posted by rugxulo in that thread: http://www.deater.net/weave/vmwprod/asm/

31 Jan 2010, 03:29

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