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    Subjectclone() and dl library incompatible?
    Hello,

    Following is a simple example that works when the dl library isn't involved
    at link time, but fails when it is.

    Here are relevant versions:

    Linux pile.franz.com 2.0.34 #1 Fri May 8 16:05:57 EDT 1998 i586 unknown
    /lib/libc-2.0.7.so
    /lib/libc.so.6
    /lib/ld.so.1.9.5

    Here's how to reproduce the problem:

    1. Make a file called ctest.c, containing:


    #include <stdio.h>
    #include <stdlib.h>
    #include <schedbits.h>

    int
    foo( void *arg )
    {
    fprintf( stderr, "in foo, pid = %d\n", getpid() );
    call_sub();
    sleep( 2 );
    }

    main()
    {
    void *stk = malloc( 1024 * 1024 );

    clone( foo, stk, CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGHAND, 0 );

    fprintf( stderr, "in main, pid = %d\n", getpid() );
    sleep( 2 );
    }

    2. Make a file called csub.c, containing:

    #include <dlfcn.h>

    int call_sub()
    {
    #ifdef WILL_BREAK_CLONE
    dlopen( "somefile", RTLD_LAZY );
    #endif
    return 0;
    }

    3. Make sure that LD_LIBRARY_PATH contains the current directory

    4. Compile, link, and run to show that it there is no problem with clone()
    when the dl library is not involved:

    cc -c csub.c
    ld -shared -o libcsub.so csub.o
    cc -o ctest ctest.c -L. -lcsub
    ctest

    (You will see:
    in main, pid = xxx
    in foo, pid = xxx+1)

    5. recompile, relink, and rerun to show that clone() fails when the dl
    library is involved:

    cc -c -DWILL_BREAK_CLONE csub.c
    ld -shared -o libcsub.so csub.o -ldl
    ctest

    (You will see:
    in main, pid = xxx) - the cloned thread will have died before running foo...

    I would appreciate any information that would help me get around this...

    Thanks,

    Steve




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