[Bug 1427981] Re: pthread_join failure

[Jan-Benedict Glaw]

I saw ESRCH problems on one of our applications, which unfortunately
leads to aborts() from within libmicrohttpd under certain circumstances.

Looking at your sample code, I guess that its main problem is the way
you're receiving the thread return value off pthread_join(). Look
carefully at it, you're getting a void * assigned to an integer
(submitted through the void ** supplied to pthread_join())! So that int
shall hold all of a pointer, which formally won't work, and may or may
not work, depending on whether or not you're on a 32 bit architecture.
You are, however, on a amd64 host, so the program isn't correct here.
-f{no-,}stack-protector may change the stack layout, that's why you're
seeing differences in testcase execution.

That said, on success, your index variable (i) is overwritten by the
NULL pointer received from the thread function on success. That's why
you always start with i=0 after a successful pthread_join().

That, unfortunately, invalidates the test case, and I need to continue
to find the root cause of my very own problem. ;-)

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https://bugs.launchpad.net/bugs/1427981

Title:
  pthread_join failure

Status in glibc package in Ubuntu:
  New

Bug description:
  pthread_join() appears to behave differently depending on gcc
  optimization is on or off. Build the attached source file with gcc -O2
  or gcc -O0 has shown different joining results.

  E.g., with `gcc pthread_join.c -lpthread -g -O2` it passes without
  issue.

  with `gcc pthread_join.c -lpthread -g -O0`, the program fails at
  pthread_join() with ESRCH.

  The same does not happen on other distros (tested on CentOS and
  Fedora).

  Some additional info:

  [macbeth at tests]$cat /etc/issue
  Ubuntu 14.04 LTS \n \l

  [macbeth at tests]$gcc --version
  gcc (Ubuntu 4.8.2-19ubuntu1) 4.8.2
  Copyright (C) 2013 Free Software Foundation, Inc.
  This is free software; see the source for copying conditions.  There is NO
  warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

  [macbeth at tests]$dpkg -l libc6
  Desired=Unknown/Install/Remove/Purge/Hold
  | Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
  |/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
  ||/ Name                                   Version                  Architecture             Description
  +++-======================================-========================-========================-==================================================================================
  ii  libc6:amd64                            2.19-0ubuntu6            amd64                    Embedded GNU C Library: Shared libraries

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