Re: What's wrong with this simple Ada w/ assembly code?

[Samuel Mize <smize@imagin.net>]

Mike Silva <mjsilva@jps.net> wrote:
> 
> robert_dewar@my-dejanews.com wrote in message
> <7bm0kb$8uj$1@nnrp1.dejanews.com>...
>>
>>GNAT simply follows the standard ABI, so if you follow
>>this you should have no trouble. If you don't know the
>>ABI, you are indeed wandering in the dark.
> 
> 
> What exactly is ABI?  I've haven't found the term in the ARM or Rationale or
> any of my books.

Application Binary Interface, if I recall correctly.  It's a standard
that defines how systems utilities are called, at the assembler level.

All the system routines will follow a consistent set of rules about how
they are to be called.  These define, for instance, what order parameters
should be on the stack, whether the caller has shifted the stack pointer
before making the call, and so on.

You *have* to follow these rules to make system calls from assembler (and
your compiler has to follow them to make those system calls for you).

You can make up your own rules for your own assembler subroutines, but
you'd be stupid to do so (in most cases).  The smartest thing is to find
out how your operating system expects subroutine calls to be coded, and
code your assembly that way.

If you do so, you're also coding it the way the compiler expects things
to be done.  So, an assembly routine that's coded in accordance with
the ABI can be called by other assembly routines, or by routines coded
in any language, if you have a half-decent compiler (or better).

Best,
Sam Mize

-- 
Samuel Mize -- smize@imagin.net (home email) -- Team Ada
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