Problems with clone and gcc

From: J.A. Magallon (jamagallon@able.es)
Date: Fri Jun 14 2002 - 19:58:01 EST

Hi all.

I write this here to see if you can give me some clue on a strange behaviour
with the clone system call. Really I want a hint about if it is a kernel
issue, a glibc(pthreads) one or a gcc issue. If sometimes it works looks
like not a kernel issue, but who knows...

Abstract: compiling a program with 'gcc -pthread' or just linking with
-lpthread (even if I just do not call any pthread_xxx), makes the
'clone()' call (glibc) fail. It does not jump to the given function.
Checked on both:
gcc (GCC) 3.1.1 (Mandrake Linux 8.3 3.1.1-0.4mdk)
gcc version 2.96 20000731 (Mandrake Linux 8.2 2.96-0.76mdk)

Sample test:

#include <sched.h>
#include <signal.h>
#include <stdio.h>

#define STSZ (4*1024)

int pslave(void *data);

int main(int argc,char** argv)
{
        int tid;
        char* stack;

        stack = (char*)valloc(STSZ);
        puts("about to clone...");
        tid = clone(pslave,stack+STSZ-1,CLONE_VM|SIGCHLD,0);
        if (tid<0)
        {
                perror("clone");
                exit(1);
        }
        puts("clone ok");

        wait(0);

        free(stack);

        return 0;
}

int pslave(void *data)
{
        puts("slave running");
        sleep(1);
        puts("slave done");

        return 0;
} 

-- 
J.A. Magallon             \   Software is like sex: It's better when it's free
mailto:jamagallon@able.es  \                    -- Linus Torvalds, FSF T-shirt
Linux werewolf 2.4.19-pre10-jam3, Mandrake Linux 8.3 (Cooker) for i586
gcc (GCC) 3.1.1 (Mandrake Linux 8.3 3.1.1-0.4mdk)
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This archive was generated by hypermail 2b29 : Sat Jun 15 2002 - 22:00:32 EST