thread-local storage doesnt work with gcc

[Frank Mehlhose]

> It looks like existing GCC's on the HP web site, including 4.2.1, were built without posix threads being enabled.

That's not true. The following code does compile with gcc 4.2.0 and works:

--------------------------------------------------
#include
#include
#define NUM_THREADS 4

static void *Work(void *num);

int main(void) {
int NumberOfThreads = NUM_THREADS;
pthread_t Worker[NUM_THREADS];

int j, ret;
for(j = 0; j < NumberOfThreads; j++) {
ret = pthread_create(&Worker[j], NULL, (void *)&Work, (void *)j);
if(ret) {
fprintf(stderr, "Error while Creating Threads\n");
return -1;
}
}

for(j = 0; j < NumberOfThreads; j++) {
pthread_join(Worker[j], NULL);
}

return 0;
}



static void *Work(void *num) {
int i;
for(i = 0; i < 100; i++) {
int j;
char buf[256]= {'\0'};
for(j = 0; j < (int)num; j++) {
sprintf(buf,"%s\t\t",buf);
}
printf("%s%d\n",buf, i);
}
return;
}
--------------------------------------------------
/opt/hp-gcc-4.2.0/bin/gcc -pthread -o parallel parallel.c && ./parallel
--------------------------------------------------

So Pthreads work on my machine with GCC and CC, but TLS does only work with CC.

MfG

[Dennis Handly]

>but TLS does only work with cc.

That's what Steve meant, gcc wasn't configured to handle the __thread keyword.

[Frank Mehlhose]

Yes, but I thought that --enable-threads=posix enables Posix-Threads (including TLS). This option seems to be set in my version of GCC. Pthreads work in both compilers, instead for TLS.

But maybe there is another Keyword that separately enables TLS-support.

[Steve Ellcey · Accepted solution]

I did some more investigation and it looks like GCC only allows thread local storage if it sees that the assembler being used also supports it. The 2.17 GNU assembler did not support thread local storage on PA and that is why GCC is not allowing it (even if compiled with --enable-threads=posix. The 2.18 GNU assembler has just recently been released and that assembler does allow thread local storage.

[Frank Mehlhose]

I think this answers my question.
Thank You