+ pthreads sqlite

Author: wyrover

3rdparty/pthreads/ANNOUNCE

@@ -0,0 +1,133 @@
+----------
+Known bugs
+----------
+
+1. Not strictly a bug, more of a gotcha.
+
+   Under MS VC++ (only tested with version 6.0), a term_func
+   set via the standard C++ set_terminate() function causes the
+   application to abort.
+
+   Notes from the MSVC++ manual:
+         1) A term_func() should call exit(), otherwise
+            abort() will be called on return to the caller.
+            A call to abort() raises SIGABRT and the default signal handler
+            for all signals terminates the calling program with
+            exit code 3.
+         2) A term_func() must not throw an exception. Therefore
+            term_func() should not call pthread_exit(), which
+            works by throwing an exception (pthreadVCE or pthreadVSE)
+            or by calling longjmp (pthreadVC).
+
+   Workaround: avoid using pthread_exit() in C++ applications. Exit
+   threads by dropping through the end of the thread routine.
+
+2. Cancellation problems in optimised code
+   - Milan Gardian
+
+   This is suspected to be a compiler bug in VC6.0, and also seen in
+   VC7.0 and VS .NET 2003. The GNU C++ compiler does not have a problem
+   with this, and it has been reported that the Intel C++ 8.1 compiler
+   and Visual C++ 2005 Express Edition Beta2 pass tests\semaphore4.c
+   (which exposes the bug).
+
+   Workaround [rpj - 2 Feb 2002]
+   -----------------------------
+   [Please note: this workaround did not solve a similar problem in
+   snapshot-2004-11-03 or later, even though similar symptoms were seen.
+   tests\semaphore4.c fails in that snapshot for the VCE version of the
+   DLL.]
+
+   The problem disappears when /Ob0 is used, i.e. /O2 /Ob0 works OK,
+   but if you want to use inlining optimisation you can be much more
+   specific about where it's switched off and on by using a pragma.
+
+   So the inlining optimisation is interfering with the way that cleanup
+   handlers are run. It appears to relate to auto-inlining of class methods
+   since this is the only auto inlining that is performed at /O1 optimisation
+   (functions with the "inline" qualifier are also inlined, but the problem
+   doesn't appear to involve any such functions in the library or testsuite).
+
+   In order to confirm the inlining culprit, the following use of pragmas
+   eliminate the problem but I don't know how to make it transparent, putting
+   it in, say, pthread.h where pthread_cleanup_push defined as a macro.
+
+   #pragma inline_depth(0)
+     pthread_cleanup_push(handlerFunc, (void *) &arg);
+
+        /* ... */
+
+     pthread_cleanup_pop(0);
+   #pragma inline_depth()
+
+   Note the empty () pragma value after the pop macro. This resets depth to the
+   default. Or you can specify a non-zero depth here.
+
+   The pragma is also needed (and now used) within the library itself wherever
+   cleanup handlers are used (condvar.c and rwlock.c).
+
+   Use of these pragmas allows compiler optimisations /O1 and /O2 to be
+   used for either or both the library and applications.
+
+   Experimenting further, I found that wrapping the actual cleanup handler
+   function with #pragma auto_inline(off|on) does NOT work.
+
+   MSVC6.0 doesn't appear to support the C99 standard's _Pragma directive,
+   however, later versions may. This form is embeddable inside #define
+   macros, which would be ideal because it would mean that it could be added
+   to the push/pop macro definitions in pthread.h and hidden from the
+   application programmer.
+
+   [/rpj]
+
+   Original problem description
+   ----------------------------
+
+   The cancellation (actually, cleanup-after-cancel) tests fail when using VC
+   (professional) optimisation switches (/O1 or /O2) in pthreads library. I
+   have not investigated which concrete optimisation technique causes this
+   problem (/Og, /Oi, /Ot, /Oy, /Ob1, /Gs, /Gf, /Gy, etc.), but here is a
+   summary of builds and corresponding failures:
+
+     * pthreads VSE (optimised tests): OK
+     * pthreads VCE (optimised tests): Failed "cleanup1" test (runtime)
+
+     * pthreads VSE (DLL in CRT, optimised tests): OK
+     * pthreads VCE (DLL in CRT, optimised tests): Failed "cleanup1" test
+   (runtime)
+
+   Please note that while in VSE version of the pthreads library the
+   optimisation does not really have any impact on the tests (they pass OK), in
+   VCE version addition of optimisation (/O2 in this case) causes the tests to
+   fail uniformly - either in "cleanup0" or "cleanup1" test cases.
+
+   Please note that all the tests above use default pthreads DLL (no
+   optimisations, linked with either static or DLL CRT, based on test type).
+   Therefore the problem lies not within the pthreads DLL but within the
+   compiled client code (the application using pthreads -> involvement of
+   "pthread.h").
+
+   I think the message of this section is that usage of VCE version of pthreads
+   in applications relying on cancellation/cleanup AND using optimisations for
+   creation of production code is highly unreliable for the current version of
+   the pthreads library.
+
+3. The Borland Builder 5.5 version of the library produces memory read exceptions
+in some tests.
+
+4. pthread_barrier_wait() can deadlock if the number of potential calling
+threads for a particular barrier is greater than the barrier count parameter
+given to pthread_barrier_init() for that barrier.
+
+This is due to the very lightweight implementation of pthread-win32 barriers.
+To cope with more than "count" possible waiters, barriers must effectively
+implement all the same safeguards as condition variables, making them much
+"heavier" than at present.
+
+The workaround is to ensure that no more than "count" threads attempt to wait
+at the barrier.
+
+5. Canceling a thread blocked on pthread_once appears not to work in the MSVC++
+version of the library "pthreadVCE.dll". The test case "once3.c" hangs. I have no
+clues on this at present. All other versions pass this test ok - pthreadsVC.dll,
+pthreadsVSE.dll, pthreadsGC.dll and pthreadsGCE.dll.