[Bug testsuite/27690] FAIL: gdb.threads/check-libthread-db.exp: user-initiated check: libpthread.so not initialized (pattern 2)

["cvs-commit at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=27690

--- Comment #4 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Tom de Vries <vries@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=6b66b5a5a29e18e1c1ddd29ea0749050d532de65

commit 6b66b5a5a29e18e1c1ddd29ea0749050d532de65
Author: Tom de Vries <tdevries@suse.de>
Date:   Tue Jul 13 15:56:49 2021 +0200

    [gdb/testsuite] Fix check-libthread-db.exp FAILs with glibc 2.33

    When running test-case gdb.threads/check-libthread-db.exp on openSUSE
    Tumbleweed with glibc 2.33, I get:
    ...
    (gdb) maint check libthread-db^M
    Running libthread_db integrity checks:^M
      Got thread 0x7ffff7c79b80 => 9354 => 0x7ffff7c79b80; errno = 0 ... OK^M
    libthread_db integrity checks passed.^M
    (gdb) FAIL: gdb.threads/check-libthread-db.exp: user-initiated check: \
      libpthread.so not initialized (pattern 2)
    ...

    The test-case expects instead:
    ...
      Got thread 0x0 => 9354 => 0x0 ... OK^M
    ...
    which is what I get on openSUSE Leap 15.2 with glibc 2.26, and what is
    described in the test-case like this:
    ...
        # libthread_db should fake a single thread with th_unique == NULL.
    ...

    Using a breakpoint on check_thread_db_callback we can compare the two
    scenarios, and find that in the latter case we hit this code in glibc
function
    iterate_thread_list in nptl_db/td_ta_thr_iter.c:
    ...
      if (next == 0 && fake_empty)
        {
          /* __pthread_initialize_minimal has not run.  There is just the main
             thread to return.  We cannot rely on its thread register.  They
             sometimes contain garbage that would confuse us, left by the
             kernel at exec.  So if it looks like initialization is incomplete,
             we only fake a special descriptor for the initial thread.  */
          td_thrhandle_t th = { ta, 0 };
          return callback (&th, cbdata_p) != 0 ? TD_DBERR : TD_OK;
        }
    ...
    while in the former case we don't because this preceding statement doesn't
    result in next == 0:
    ...
      err = DB_GET_FIELD (next, ta, head, list_t, next, 0);
    ...

    Note that the comment mentions __pthread_initialize_minimal, but in both
cases
    it has already run before we hit the callback, so it's possible the comment
is
    no longer accurate.

    The change in behaviour bisect to glibc commit 1daccf403b "nptl: Move stack
    list variables into _rtld_global", which moves the initialization of stack
    list variables such as __stack_user to an earlier moment, which explains
well
    enough the observed difference.

    Fix this by updating the regexp patterns to agree with what libthread-db is
    telling us.

    Tested on x86_64-linux, both with glibc 2.33 and 2.26.

    gdb/testsuite/ChangeLog:

    2021-07-07  Tom de Vries  <tdevries@suse.de>

            PR testsuite/27690
            * gdb.threads/check-libthread-db.exp: Update patterns for glibc
2.33.

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