[3.3.1]: thread local storage - what do I need?

["Marshall, Simon" <simon.marshall@xxxxxxxxx>]

Hi, I've been trying to use the thread local storage "__thread"
attribute with gcc (gcc-3.3.1) and SuSE 8.2 (Linux 2.4.20-4GB) without
any success.  The GCC manual says TLS requires support from ld, ld.so,
libc.so and libpthread.so, but I cannot find out exactly what I need,
whether I have it and how I get it.

I have a function defined in file __thread.cpp as:

#include <stdio.h>
#include <pthread.h>

__thread		// make "p" thread-local.
pthread_t p = 0;

extern "C" void *foo (void *)
{
    int j = 0;
    p = pthread_self();
    printf ("thread %d starts\n", p); fflush (stdout);
    for (int i = 0; i < 10 * 1000 * 1000; i++)
        j += i;
    printf ("thread %d ends\n", p); fflush (stdout);
    return NULL;
}

I build a shared library like this:

gcc -g -D_REENTRANT -fpic -W -c __thread.cpp -o __thread.o	# don't
need -ftls-model= here
gcc -shared __thread.o -o lib__thread.so

I then link the library to a file containing main() that creates several
threads running function foo() like this:

gcc -g -D_REENTRANT -fpic -W -L. -l__thread -lpthread  __threadmain.cpp
./lib__thread.so: undefined reference to `___tls_get_addr'
collect2: ld returned 1 exit status

Does this mean I don't have the necessary support for TLS?  What do I
need to get support for it?  If I build without the __thread attribute
it works (except that p has a single value of course).  With that
executable I also get:

% ldd ./a.out 
        libpthread.so.0 => /lib/libpthread.so.0 (0x40022000)
        libc.so.6 => /lib/libc.so.6 (0x40073000)
        /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)

Please can you shed any light on this or show me where to look?  Thanks,
Simon.

Simon Marshall, Misys Risk Management Systems
1 St. George's Road, Wimbledon, London SW19 4DR, UK
Email: simon.marshall@xxxxxxxxx Web: www.misys.com
Phone: +44 20 8879 1188 Fax: +44 20 8879 1764

NB: FWIW, if I just build an executable from a file with both main() and
foo(), i.e., not a shared library, then the build is OK but SEGVs at the
call to pthread_self() like this:

% gcc -g -D_REENTRANT -fpic -lpthread thread__.cpp 
% ./a.out 
Segmentation fault
% ldd ./a.out			# Get this!?
        not a dynamic executable
% gdb ./a.out
(gdb) run
Starting program: /home/marshals/tmp/a.out 
[New Thread 16384 (LWP 9493)]
[New Thread 32769 (LWP 9494)]
[New Thread 16386 (LWP 9495)]
[New Thread 32771 (LWP 9496)]
[New Thread 49156 (LWP 9497)]
[New Thread 65541 (LWP 9498)]
BFD: BFD 2.13.90 20020903 assertion fail libbfd.c:1132
[repeats]

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 65541 (LWP 9498)]
0x08048635 in foo () at thread__.cpp:12
12          p = pthread_self();