TLS on x86-64 question..

[Andreas Jaeger]

Jakub Jelinek <jakub@redhat.com> writes:

> On Fri, Sep 05, 2003 at 11:57:56AM +0200, Andreas Jaeger wrote:
>> 
>> If I compile the following small program on x86-64 (with either GCC
>> 3.3 CVS, GCC 3.3 hammer-branch CVS or 3.4 CVS) I get the following
>> error:
>> 
>> $ /opt/gcc/3.3-devel/bin/gcc  -g -c tls.c -o tls.o -fPIC -ftls-model=local-exec
>> $ /opt/gcc/3.3-devel/bin/gcc -g -o tls.so -shared tls.o
>> /usr/bin/ld: tls.o: relocation R_X86_64_TPOFF32 can not be used when making a shared object; recompile with -fPIC
>> tls.o: could not read symbols: Bad value
>> collect2: ld returned 1 exit status
>> 
>> The program is:
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> static __thread int foo;
>> 
>> int getTLSVar(void)
>> {
>>     return foo; 
>> } 
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> 
>> This works fine on other platforms, e.g. i386.
>> 
>> Jakub, any ideas on this one?
>
> local-exec is not supported in shared libraries on x86_64 (well, it is not
> supported on most arches).

In that case shouldn't gcc already reject the combination -fPIC
-ftls-model=local-exec?

> It is the same thing as supporting -fno-pic code in shared libraries
> - local-exec would mean TLS relocations against .text segment.

Ok, understood.

Thanks for the explanation,
Andreas
-- 
 Andreas Jaeger, aj@suse.de, http://www.suse.de/~aj
  SuSE Linux AG, Deutschherrnstr. 15-19, 90429 Nürnberg, Germany
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