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Date: Fri, 20 Jan 2006 17:15:17 +0530
From: Sudhahar <jsudha80 AT gmail DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: Need information about data and bss segment address access in cygwin
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Thanks Dave your reply answered the question where they declared. But
how does these variables get the segment address of data and bss for a
running process to make a copy to the child process? This is the
questions which is a puzzle to me.

Thanks in Advance for your answer
Sudha

On 1/20/06, Dave Korn <dave DOT korn AT artimi DOT com> wrote:
> Sudhahar wrote:
>
> > from parent process to child process. After trying to find where the
> > data_start and data_end get the address of running process data and
> > bss segment, I ended up with a declaration  of
> >
> > extern char _data_start__, _data_end__, _bss_start__, _bss_end__; in
> > file Winsup.h
> >
> > There is no other place where _data_start__, _data_end__,
> > _bss_start__, _bss_end__ are defined they act as external symbols for
> > cygwin.
> >
> > Can anyone through some light on where these variables are actually
> > declared and how they get the running process segment addresses.
>
>   They are generated by the linker.  Take a look at the linker script by
> running "ld --verbose".
>
> dk AT espanola /usr/build/src-binutils/bfd> ld --verbose  | grep _start
>      to include this between __data_start__ and __data_end__, but that
>     __data_start__ = . ;
>     __bss_start__ = . ;
>     ___crt_xc_start__ = . ;
>     ___crt_xi_start__ = . ;
>     ___crt_xl_start__ = . ;
>     ___crt_xp_start__ = . ;
>     ___crt_xt_start__ = . ;
>     ___tls_start__ = . ;
> dk AT espanola /usr/build/src-binutils/bfd> ld --verbose  | grep _end
>      to include this between __data_start__ and __data_end__, but that
>      ".data_cygwin_nocopy" and explictly include it after __data_end__. */
>     __data_end__ = . ;
>     __bss_end__ = . ;
>     ___crt_xc_end__ = . ;
>     ___crt_xi_end__ = . ;
>     /* ___crt_xl_end__ is defined in the TLS Directory support code */
>     ___crt_xp_end__ = . ;
>     ___crt_xt_end__ = . ;
>     ___tls_end__ = . ;
>     PROVIDE ( _end = .);
>      __end__ = .;
> dk AT espanola /usr/build/src-binutils/bfd>
>
>
>     cheers,
>       DaveK
> --
> Can't think of a witty .sigline today....
>
>
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