Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.sys.acorn.programmer > #585

Re: AIF header - how?

Show all headers | View raw

The following bytes were arranged on 11 Aug 2011 by Bob Latham :

> Hi,
>
> I've just found out that none of the programs I've ever written will run
> on OS6.20. They all give an error message "The application uses an
> obsolete executable file format which is no longer supported by RISC OS".
>
> After a large amount of googling it seems I need to provide an AIF header.

An AIF header is what files of type Absolute (&FF8) typically start
with.  I don't know specifics, but I do know that it's of a fixed size,
and that the first 16 bytes (4 words) are all either branch commands to
various areas of the program which are defined to do certain tasks, or
"MOV R0,R0" if not applicable to this program.  The first instruction
jumps to decompression code, if the executable is compressed, and I
think the fourth jumps to the program proper.  The fifth word is always
the instruction "SWI OS_Exit".

AIF headers are generated automatically by all C compilers, with the
exception of recent versions of GCC which enforce a Unix format called
ELF instead, so if your program didn't work then it wasn't written in C.

There's no practical reason why a program shouldn't run without an AIF
header, but ROL in their infinite wisdom have decided suddenly to
enforce a whole lot of standards for no particular reason at all,
including some (like the Utility header) which didn't even exist before
they enforced them.  The reason invariably given is 32-bit
compatibility, and the capability to automatically patch old software to
run on new machines, which is a bit rich given that none of ROL's modern
products run on a 32-bit machine and Acorn's patch mechanism has never
once been used in its 15-year history.

The underlying problem is the same as the one which infamously caused
ROL OSes to start refusing to run binaries compressed using modern
versions of the Squeeze tool - the notorious "Unable to start
application (decompression failed)" error, in spite of the fact that
there was nothing actually wrong with the binaries.

However, unlike the decompression problem, ROL *have* built in a
workaround for the AIF problem.  In Configure, there's a section called
"Compatibility", in which every single option button should be ticked.
If you do this, Configure will warn you that you are potentially
jeopardising your computer by running unstable software.  Ignore it,
it's lying - unless you consider your software, and a lot of other
long-used programs, to be unstable.

-- 
  __<^>__   Red sky in the morning: Shepherd's warning
 / _   _ \  Red sky at night: Shepherd's delight
( ( |_| ) ) Mince and potatoes: Shepherd's pie
 \_>   <_/  ======================= Martin Bazley ==========================

Back to comp.sys.acorn.programmer | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

AIF header - how? Bob Latham <bob@sick-of-spam.invalid> - 2011-08-11 12:11 +0100
  Re: AIF header - how? Martin Bazley <martin.bazley@blueyonder.co.uk> - 2011-08-11 16:43 +0100
    Re: AIF header - how? Bob Latham <bob@sick-of-spam.invalid> - 2011-08-11 17:21 +0100
      Re: AIF header - how? cferris@freeRemoveuk.com.invalid - 2011-08-11 20:11 +0100
        Re: AIF header - how? Bob Latham <bob@sick-of-spam.invalid> - 2011-08-11 21:19 +0100
          Re: AIF header - how? John Tytgat <this@is.invalid> - 2011-08-12 12:58 +0200
            Re: AIF header - how? cferris@freeRemoveuk.com.invalid - 2011-08-12 13:11 +0100
              Re: AIF header - how? druck <news@druck.org.uk> - 2011-08-13 15:09 +0100
        Re: AIF header - how? jgharston <jgh@arcade.demon.co.uk> - 2011-08-11 15:49 -0700
  Re: AIF header - how? Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2011-08-13 00:57 +0200
  Re: AIF header - how? Bob Latham <bob@sick-of-spam.invalid> - 2011-08-13 10:42 +0100

csiph-web