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Diffstat (limited to 'BUGS')
| -rw-r--r-- | BUGS | 102 |
1 files changed, 102 insertions, 0 deletions
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+Known bugs
+----------
+
+1. Under MS VC++ (only tested with version 6.0), a term_func
+ set via the standard C++ set_terminate() function is not called.
+
+ 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
+
+ Workaround [rpj - 2 Feb 2002]
+ -----------------------------
+ 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.
+
+
+
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