Date: Wed, 23 Apr 1997 11:53:21 +0930 (CST) From: Michael Smith <msmith@atrad.adelaide.edu.au> To: terry@lambert.org (Terry Lambert) Cc: msmith@atrad.adelaide.edu.au, rssh@cki.ipri.kiev.ua, freebsd-hackers@FreeBSD.org Subject: Re: Dynamic linking libraries [Q] Message-ID: <199704230223.LAA18646@genesis.atrad.adelaide.edu.au> In-Reply-To: <199704222058.NAA27156@phaeton.artisoft.com> from Terry Lambert at "Apr 22, 97 01:58:15 pm"
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Terry Lambert stands accused of saying:
> >
> > If you are referring to interprocess communication using static
> > variables in a DLL, I think people here might be very ill. 8)
>
> I believe what he is referring to is that the MS executables put the
> library-specific data segment into the DLL rather than statically
> linking it with the program, as BSD does.
Um, you are saying that if I link against a shared library, the
.data segment from that library is linked into my executable at
compile time?
I honestly cannot believe that this is the case. eg. :
cain:~/work/foo>cat testprog.c
#include <stdio.h>
#include <errno.h>
main() {
printf("%s\n", sys_errlist[E2BIG]);
}
cain:~/work/foo>./testprog
Argument list too long
cain:~/work/foo>strings -n 8 testprog
/usr/libexec/ld.so
Couldn't open
Failure reading ld.so
Bad magic: ld.so
Cannot map ld.so (text)
Cannot map ld.so (data)
Cannot map ld.so (bss)
ld.so failed
Service unavailable
__DYNAMIC
__exit_dummy_decl
_dlclose
_dlerror
___do_global_dtors
___DTOR_LIST__
___CTOR_LIST__
___do_global_ctors
___progname
_sys_errlist
__exit_dummy_ref
_environ
I certainly don't see the static data from libc there.
> The biggest example in FreeBSD's sordid static data history is the
> change in the handling of sys_errlist[], which might have been
> entirely opaque between libc.so revisions, assuing the program itself
> did not reference it (a bogus thing for a program to do anyway).
>
> If that were the case, a program which pulled the data in from the
> shared library instead of pulling it into the program image at link
> time would have continued to function. Instead, the entire FreeBSD
> world blew up.
I think you must be thinking of something else.
> Terry Lambert
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