Local Symbol Names

Local Symbol Names

[S kris]

Hi,

In some of the assembly files, it's noticed that Local Symbol Names have 
been used that in the following way,

     ................
     call 0f
0: popl %eax
    ................
The call is referring to immediately next statement. Please help me in 
finding out the significance of the above lines in the assembly code.

Thanks

Kris

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Re: Local Symbol Names

[Slack Traq]

--- S kris <kris_bs@hotmail.com> wrote:
> Hi,
> 
> In some of the assembly files, it's noticed that
> Local Symbol Names have 
> been used that in the following way,
> 
>      ................
>      call 0f
> 0: popl %eax
>     ................
> The call is referring to immediately next statement.
> Please help me in 
> finding out the significance of the above lines in
> the assembly code.
> 
> Thanks
> 
> Kris

Kris: the 'f' after the 'O' in the call statement is
really unnecessary because the label begins in the
next statement. Maybe is a call to a "far" function or
label, but is quite obvious that 'O' is not such
label.
I hope this will help you.
Regards,
                                          Slack

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Re: Local Symbol Names

[hpr]

Slack Traq am Mittwoch, 25. Juni 2003 17:09:
> --- S kris <kris_bs@hotmail.com> wrote:
> > Hi,
> >
> > In some of the assembly files, it's noticed that
> > Local Symbol Names have
> > been used that in the following way,
> >
> >      ................
> >      call 0f
> > 0: popl %eax
> >     ................
> > The call is referring to immediately next statement.
> > Please help me in
> > finding out the significance of the above lines in
> > the assembly code.
> >
> > Thanks
> >
> > Kris
>
> Kris: the 'f' after the 'O' in the call statement is
> really unnecessary because the label begins in the
> next statement. Maybe is a call to a "far" function or
> label, but is quite obvious that 'O' is not such

nonsense! (assumed the code is from binutils' AS)

numeric labels can be redefined.
they are directionally referred, "f"orward  or "b"ackword

the example fetches the address at label '0' to eax, which can be used to 
supporting position independent code.

best,
	hp


> label.
> I hope this will help you.
> Regards,
>                                           Slack
>
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Re: Local Symbol Names

[Jack Dennon]

On Wednesday 25 June 2003 01:23, S kris wrote:
> Hi,
>
> In some of the assembly files, it's noticed that Local Symbol Names have
> been used that in the following way,
>
>      ................
>      call 0f
> 0: popl %eax
>     ................
> The call is referring to immediately next statement. Please help me in
> finding out the significance of the above lines in the assembly code.
>
> Thanks
>
> Kris
>
	The call instruction probably was used to empty the
	the Execution Unit's instruction cache; thereby
	forcing it to be reloaded from memory. Or, it could
	be used just to force a time delay.
	jdennon@seasurf.com

Re: Local Symbol Names

[Brian Raiter]

>	The call instruction probably was used to empty the
>	the Execution Unit's instruction cache; thereby
>	forcing it to be reloaded from memory. Or, it could
>	be used just to force a time delay.

The pop %eax instruction, however, makes it clear that the purpose of
the code is to get the current PC address into eax. As hpr suggested,
almost certainly for use in writing position-independent code.

b

Re: Local Symbol Names

[Jack Dennon]

On Wednesday 25 June 2003 12:44, Brian Raiter wrote:
> >	The call instruction probably was used to empty the
> >	the Execution Unit's instruction cache; thereby
> >	forcing it to be reloaded from memory. Or, it could
> >	be used just to force a time delay.
>
> The pop %eax instruction, however, makes it clear that the purpose of
> the code is to get the current PC address into eax. As hpr suggested,
> almost certainly for use in writing position-independent code.
>
	Hmm, yes you have a point.
	But then, why not just push and pop?
	jdennon@seasurf.com