[Alexandre Oliva <oliva@dcc.unicamp.br>] Re: libtool doesn't work well on FreeBSD2

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From: Alexandre Oliva (oliva@dcc.unicamp.br)
Date: Sun Jan 17 1999 - 01:48:34 EST

Thought you might be interested in knowing why Kaffe hasn't worked on
FreeBSD during the last week... 

-- 
Alexandre Oliva  http://www.dcc.unicamp.br/~oliva  aoliva@{acm.org}
oliva@{dcc.unicamp.br,gnu.org,egcs.cygnus.com,samba.org}
Universidade Estadual de Campinas, SP, Brasil
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Resent-Date: Sun, 17 Jan 1999 01:48:13 -0500
To: Alex Zepeda <garbanzo@hooked.net>
Cc: bug-libtool@gnu.org
Subject: Re: libtool doesn't work well on FreeBSD2
From: Alexandre Oliva <oliva@dcc.unicamp.br>
Date: 17 Jan 1999 04:39:32 -0200
Message-ID: <or90f2flnf.fsf@araguaia.dcc.unicamp.br>
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There's a strange interaction of -fPIC with -lm, see:

bash$ gcc -v
gcc version 2.7.2.1
bash$ uname -a
FreeBSD marker.cs.utah.edu 2.2.6-BETA FreeBSD 2.2.6-BETA #0: Mon Aug 24 17:45:26 MDT 1998     sclawson@marker.cs.utah.edu:/usr/src/sys/compile/MARKER  i386
bash$ cat t.c
int i; main() { i = 1; }
bash$ gcc t.c -lm
bash$ ./a.out
bash$ gcc -fPIC t.c
bash$ ./a.out
bash$ gcc -fPIC t.c -lm
bash$ ./a.out
bash$ gcc -fPIC t.c -lm -lm
bash$ ./a.out
bash$ gcc -lm t.c
bash$ ./a.out
bash$ gcc -fPIC -lm t.c
ld: symbol __GLOBAL_OFFSET_TABLE_ remains undefined
bash$ ./a.out
Segmentation fault (core dumped)
bash$ gcc -fPIC -lm t.c -lm
ld: symbol __GLOBAL_OFFSET_TABLE_ remains undefined
bash$ ./a.out
Segmentation fault (core dumped)

Note that the program does not depend on `-lm' in anyway.  
Nevertheless, the presence of `-lm' flag affects the output of `ld',
and also the result of the program.

The assembly output of gcc (not included) seems correct.
Nevertheless, when the program that lacks the __GLOBAL_OFFSET_TABLE is
run, it crashes in the instruction that tries to write to the global
variable `i', which is expected given the linker error, because the
base address in $ebx wasn't properly relocated.

Any suggestions on how to make linking PIC objects more reliable, for
the benefit of GNU libtool?

Note that this program was reduced from a more complex test case of
libtool, in which -lm appeared after all objects with non-PIC code,
but before other libraries with PIC code.

-- 
Alexandre Oliva  http://www.dcc.unicamp.br/~oliva  aoliva@{acm.org}
oliva@{dcc.unicamp.br,gnu.org,egcs.cygnus.com,samba.org}
Universidade Estadual de Campinas, SP, Brasil

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