Author Topic: converting gcc produced *.S files to NASM  (Read 6566 times)

nobody

  • Guest
converting gcc produced *.S files to NASM
« on: March 08, 2005, 12:33:35 PM »
Hi
I'm a newbie to NASM.
I have sample c program and i did generate assembly file
from gcc in intel mode.
%gcc -masm=intel sample.c
When i try to generate object code from  NASM it fails with parsing errors.
I tried to use A2I tool to convert AT&T syntax to
Intel.It didn't help either.
Does anybody know what coudl be the problem.

bw
John

Offline Frank Kotler

  • NASM Developer
  • Hero Member
  • *****
  • Posts: 2379
  • Country: us
Re: converting gcc produced *.S files to NASM
« Reply #1 on: March 08, 2005, 03:30:38 PM »
Hi John,

There are differences between Nasm syntax and what gcc/gas consider "Intel syntax". The "converters" - I've used intel2gas more than A2I - take care of much of the "grunt work", but typically require some "hand editing" before the results will assemble properly with Nasm. I don't imagine using *both* "-masm intel" and a "converter" will work.

Take a close look at the lines Nasm is complaining about. You *may* be able to just comment 'em out, if you're lucky. If they're a vital part of the code, you'll have to figure out what the code *has* to do at that point (to work as intended), and then figure out what syntax will persuade Nasm to do that. In most cases, this isn't as hard as it sounds - you might need to RTFM or look at more Nasm examples to learn Nasm's ways...

Or, post the offending lines here - we can probably help you get Nasm to swallow 'em. Hard to say just what the problem is without more information.

Best,
Frank

kabbin

  • Guest
Re: converting gcc produced *.S files to NASM
« Reply #2 on: June 04, 2007, 02:54:44 AM »
Dear all:
   I converted gcc produced *.S files to NASM by att2intel.
But I found that it can't convert function declaraction or some psudo instructions?
such as :
    .globl function1  (can't convert )
or
    .align 16
(which converted by att2intel to .align 65536,and I wonder is it right?)

rounding_512 : .fill 4,4,512  (can't convert also!)
So I rewrite by hand as following:
rounding_512 : dw 512 512 512 512 512 512 512 512

So, could anyone tell me how to declare a function in nasm? Is it the same way as MASM? (PROC and ENDP)  Thanks.

nobody

  • Guest
Re: converting gcc produced *.S files to NASM
« Reply #3 on: June 04, 2007, 05:05:13 AM »
Hi Kabbin,

>    I converted gcc produced *.S files to NASM by att2intel.
> But I found that it can't convert function declaraction or some psudo
> instructions?
> such as :
>     .globl function1  (can't convert )

That's surprising. I'd have expected that to convert "easily" to "global function1"...

> or
>     .align 16
> (which converted by att2intel to .align 65536,and I wonder is it right?)

I don't think so. I'd expect just "align 16".

> rounding_512 : .fill 4,4,512  (can't convert also!)
> So I rewrite by hand as following:
> rounding_512 : dw 512 512 512 512 512 512 512 512

I'm not familiar with "fill", but something I saw recently suggested that the second parameter was "size"... so you might want "dd" rather than "dw"? If you get unexpected results, try that.

> So, could anyone tell me how to declare a function in nasm? Is it the same way
> as MASM? (PROC and ENDP)  Thanks.

You'll have to "%include" a macro file if you want "proc" and "endp". There are several in the "misc/" directory that have it. If you want to export a function from a shared library, "global myfunc:function" (elf only).

Best,
Frank