Subj : Re: Inline Assembler bug with structs of certain size
To   : borland.public.cpp.borlandcpp
From : Jeremy
Date : Fri Dec 03 2004 08:58 am

Ed,

Thanks for the prompt reply.

I see you're not getting the same results as me. In fact, both of yours seem
to give erroneous results from the inline assembler functions (should return
the same value as &TestStruct or 0xEEEE - I assigned this value to _AX just
to illustrate that the routine does nothing at all when the structure is the
"wrong" size).

I had noticed that choosing "C to Assembler" compile in the IDE would give
me correct assembler code, but going direct to object didn't. Also, changing
TestStruct to a char array the same length doesn't exhibit the same weird
result (unfortunately this isn't a viable option for my real-world code, at
least, not a readable option).

I have managed a workaround in the meantime - I'm setting up the pointers to
& length of the structure prior to scanning using the _ES, _DI & _CX
pseudovariables just prior to the inline assembly & the code's identical to
the old assembly. So in that sense I've "cured" my problem, but I'd love to
know the mechanism behind the weirdness - especially the fact that it only
occurs over a certain (reasonably large) range of sizes.

Jeremy

"Ed Mulroy [TeamB]" <dont_email_me@bitbuc.ket> wrote in message
news:41ae9b91$1@newsgroups.borland.com...
> Here is what you posted handled with BC++ 5.02.  Note
> that -B is for compile via assembly and without -B it uses
> the built in assembler (BASM) which won't align the code
> on boundaries the same as is done when generating an
> assembly language file and passing it to Tasm.  If I were
> doing embedded work such as you are, I'd use -B and
> add -TL to the command line so that I'd have a listing.
>
> It's late now (11:30 PM) and I'm tired.  I'll look at it a bit more
> tomorrow.
>
> ------------------
> F:\Projects\lookat\q408
> >bcc -1 -tDe -ml -B ques408.c
> Borland C++ 5.2 Copyright (c) 1987, 1997 Borland International
> Mar 19 1997 17:29:40
> ques408.c:
> Turbo Assembler  Version 4.1  Copyright (c) 1988, 1996 Borland
International
>
> Assembling file:   ques408.ASM
> Error messages:    None
> Warning messages:  None
> Passes:            1
> Remaining memory:  400k
>
> Turbo Link  Version 7.1.32.2. Copyright (c) 1987, 1996 Borland
International
>
> F:\Projects\lookat\q408
> >ques408
> length of asm_test1 = 8
> &TestStruct1 = 0b70, via asm = 1441
> length of asm_test2 = 8
> &TestStruct2 = 594a, via asm = 1441
>
> F:\Projects\lookat\q408
> >bcc -1 -tDe -ml ques408.c
> Borland C++ 5.2 Copyright (c) 1987, 1997 Borland International
> Mar 19 1997 17:29:40
> ques408.c:
> Turbo Link  Version 7.1.32.2. Copyright (c) 1987, 1996 Borland
International
>
> F:\Projects\lookat\q408
> >ques408
> length of asm_test1 = 8
> &TestStruct1 = 0b70, via asm = 1441
> length of asm_test2 = 5
> &TestStruct2 = 594a, via asm = 1441
>
> F:\Projects\lookat\q408
> >
> ------------------
>
> .  Ed
>
> > Jeremy wrote in message
> > news:41ae833d$1@newsgroups.borland.com...
> >
> > I found an interesting bug in the BC5.0B inline assembler
> > today (after a couple of days tracking it down). I mention
> > it here because it may still exist in newer versions.
> >

.