gas and gcc

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Article #151

#151

From: Martin Cote
Date: Sat, 24 Nov 2001 00:16

47 lines
2530 bytes

Hi,

I'm trying to write some C modules in assembly.  I'm using 'gcc' and
'as' under linux.  I'm trying some test to 'get the feel' of this hybrid
programming.  I'm trying a simple 'write_char' function that display the
char passed in parameter on the screen.  Here's my source code :
extern write_char(char);
----------------------------------
..globl write_char

write_char:
 pushl %ebp
 movl  %esp,%ebp
 movl  $4,%eax
 xorl  %ebx,%ebx
 incl  %ebx
 movl  4(%esp),%ecx
 movl  %ecx,char
 leal  char,%ecx
 xorl  %edx,%edx
 incl  %edx
 int   $0x80
 leave
 ret

char: .byte 0,0,0,0
----------------------------------

And the C main :

----------------------------------
extern write_char(char);

int main() {
  write_char(97);
  return 0;
}
----------------------------------

The problem is that it get a 'core dump' ;)
There is something that I did not undersand in the way to pass
parameters to a C function (with the %esp register).

If anyone can help, I would be really grantful...

Thank you very much
Martin

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From: Martin Cote <vlrcfmnw@videotron.ca>
Newsgroups: comp.lang.asm.x86,alt.lang.asm,gnu.gcc
Subject: gas and gcc
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