Re: [9fans] 8l(1) PUSH/POP

[Eris Discordia <eris.discordia@gmail.com>]

> what is the reason behind 8l(1) not allowing unbalanced PUSH/POP?

I remember I used to first thing balance and match pushes and pops at the
beginning and end of a PROC when I was trying to program in (16-bit) x86
assembly. One unbalanced or mismatched push or pop could result in wrong
values ending up in the wrong registers (PUSH AX ... POP SI!). This
normally voluntary process and implications of doing it wrong seem
important enough to warrant a linker trying to safeguard against the
possible mistake.

I also seem to remember caveats on the use of certain software interrupts
(BIOS routines) and/or MS-DOS (INT 21h) API calls with certain registers
because those procedures for one reason or another would modify contents of
registers that were not considered part of their output. It was often
advised to use a matched push and pop pair around such calls and quite a
number of times I forgot to match a push with a pop resulting in serious
failure.



--On Friday, November 06, 2009 10:22 -0200 Iruata Souza
<iru.muzgo@gmail.com> wrote:

> hello,
>
> what is the reason behind 8l(1) not allowing unbalanced PUSH/POP?
>
> thanks,
> iru
>