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| Original file line number | Original file line | Diff line number | Diff line change |
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| @@ -1,114 +1,114 @@ | |||
| ---------- | ---------- | ||
| Known bugs | Known bugs | ||
| ---------- | ---------- | ||
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| 1. Not strictly a bug, more of a gotcha. | 1. Not strictly a bug, more of a gotcha. | ||
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| Under MS VC++ (only tested with version 6.0), a term_func | Under MS VC++ (only tested with version 6.0), a term_func | ||
| set via the standard C++ set_terminate() function causes the | set via the standard C++ set_terminate() function causes the | ||
| application to abort. | application to abort. | ||
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| Notes from the MSVC++ manual: | Notes from the MSVC++ manual: | ||
| 1) A term_func() should call exit(), otherwise | 1) A term_func() should call exit(), otherwise | ||
| abort() will be called on return to the caller. | abort() will be called on return to the caller. | ||
| A call to abort() raises SIGABRT and the default signal handler | A call to abort() raises SIGABRT and the default signal handler | ||
| for all signals terminates the calling program with | for all signals terminates the calling program with | ||
| exit code 3. | exit code 3. | ||
| 2) A term_func() must not throw an exception. Therefore | 2) A term_func() must not throw an exception. Therefore | ||
| term_func() should not call pthread_exit(), which | term_func() should not call pthread_exit(), which | ||
| works by throwing an exception (pthreadVCE or pthreadVSE) | works by throwing an exception (pthreadVCE or pthreadVSE) | ||
| or by calling longjmp (pthreadVC). | or by calling longjmp (pthreadVC). | ||
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| Workaround: avoid using pthread_exit() in C++ applications. Exit | Workaround: avoid using pthread_exit() in C++ applications. Exit | ||
| threads by dropping through the end of the thread routine. | threads by dropping through the end of the thread routine. | ||
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| 2. Cancellation problems in optimised code | 2. Cancellation problems in optimised code | ||
| - Milan Gardian | - Milan Gardian | ||
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| This is suspected to be a compiler bug in VC6.0, and also seen in | 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 | 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 | 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 | and Visual C++ 2005 Express Edition Beta2 pass tests\semaphore4.c | ||
| (which exposes the bug). | (which exposes the bug). | ||
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| Workaround [rpj - 2 Feb 2002] | Workaround [rpj - 2 Feb 2002] | ||
| ----------------------------- | ----------------------------- | ||
| [Please note: this workaround did not solve a similar problem in | [Please note: this workaround did not solve a similar problem in | ||
| snapshot-2004-11-03 or later, even though similar symptoms were seen. | 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 | tests\semaphore4.c fails in that snapshot for the VCE version of the | ||
| DLL.] | DLL.] | ||
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| The problem disappears when /Ob0 is used, i.e. /O2 /Ob0 works OK, | 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 | 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. | specific about where it's switched off and on by using a pragma. | ||
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| So the inlining optimisation is interfering with the way that cleanup | So the inlining optimisation is interfering with the way that cleanup | ||
| handlers are run. It appears to relate to auto-inlining of class methods | 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 | since this is the only auto inlining that is performed at /O1 optimisation | ||
| (functions with the "inline" qualifier are also inlined, but the problem | (functions with the "inline" qualifier are also inlined, but the problem | ||
| doesn't appear to involve any such functions in the library or testsuite). | doesn't appear to involve any such functions in the library or testsuite). | ||
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| In order to confirm the inlining culprit, the following use of pragmas | 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 | 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. | it in, say, pthread.h where pthread_cleanup_push defined as a macro. | ||
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| #pragma inline_depth(0) | #pragma inline_depth(0) | ||
| pthread_cleanup_push(handlerFunc, (void *) &arg); | pthread_cleanup_push(handlerFunc, (void *) &arg); | ||
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| /* ... */ | /* ... */ | ||
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| pthread_cleanup_pop(0); | pthread_cleanup_pop(0); | ||
| #pragma inline_depth() | #pragma inline_depth() | ||
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| Note the empty () pragma value after the pop macro. This resets depth to the | Note the empty () pragma value after the pop macro. This resets depth to the | ||
| default. Or you can specify a non-zero depth here. | default. Or you can specify a non-zero depth here. | ||
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| The pragma is also needed (and now used) within the library itself wherever | The pragma is also needed (and now used) within the library itself wherever | ||
| cleanup handlers are used (condvar.c and rwlock.c). | cleanup handlers are used (condvar.c and rwlock.c). | ||
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| Use of these pragmas allows compiler optimisations /O1 and /O2 to be | Use of these pragmas allows compiler optimisations /O1 and /O2 to be | ||
| used for either or both the library and applications. | used for either or both the library and applications. | ||
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| Experimenting further, I found that wrapping the actual cleanup handler | Experimenting further, I found that wrapping the actual cleanup handler | ||
| function with #pragma auto_inline(off|on) does NOT work. | function with #pragma auto_inline(off|on) does NOT work. | ||
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| MSVC6.0 doesn't appear to support the C99 standard's _Pragma directive, | MSVC6.0 doesn't appear to support the C99 standard's _Pragma directive, | ||
| however, later versions may. This form is embeddable inside #define | however, later versions may. This form is embeddable inside #define | ||
| macros, which would be ideal because it would mean that it could be added | 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 | to the push/pop macro definitions in pthread.h and hidden from the | ||
| application programmer. | application programmer. | ||
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| [/rpj] | [/rpj] | ||
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| Original problem description | Original problem description | ||
| ---------------------------- | ---------------------------- | ||
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| The cancellation (actually, cleanup-after-cancel) tests fail when using VC | The cancellation (actually, cleanup-after-cancel) tests fail when using VC | ||
| (professional) optimisation switches (/O1 or /O2) in pthreads library. I | (professional) optimisation switches (/O1 or /O2) in pthreads library. I | ||
| have not investigated which concrete optimisation technique causes this | have not investigated which concrete optimisation technique causes this | ||
| problem (/Og, /Oi, /Ot, /Oy, /Ob1, /Gs, /Gf, /Gy, etc.), but here is a | problem (/Og, /Oi, /Ot, /Oy, /Ob1, /Gs, /Gf, /Gy, etc.), but here is a | ||
| summary of builds and corresponding failures: | summary of builds and corresponding failures: | ||
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| * pthreads VSE (optimised tests): OK | * pthreads VSE (optimised tests): OK | ||
| * pthreads VCE (optimised tests): Failed "cleanup1" test (runtime) | * pthreads VCE (optimised tests): Failed "cleanup1" test (runtime) | ||
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| * pthreads VSE (DLL in CRT, optimised tests): OK | * pthreads VSE (DLL in CRT, optimised tests): OK | ||
| * pthreads VCE (DLL in CRT, optimised tests): Failed "cleanup1" test | * pthreads VCE (DLL in CRT, optimised tests): Failed "cleanup1" test | ||
| (runtime) | (runtime) | ||
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| Please note that while in VSE version of the pthreads library the | 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 | 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 | VCE version addition of optimisation (/O2 in this case) causes the tests to | ||
| fail uniformly - either in "cleanup0" or "cleanup1" test cases. | fail uniformly - either in "cleanup0" or "cleanup1" test cases. | ||
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| Please note that all the tests above use default pthreads DLL (no | Please note that all the tests above use default pthreads DLL (no | ||
| optimisations, linked with either static or DLL CRT, based on test type). | optimisations, linked with either static or DLL CRT, based on test type). | ||
| Therefore the problem lies not within the pthreads DLL but within the | Therefore the problem lies not within the pthreads DLL but within the | ||
| compiled client code (the application using pthreads -> involvement of | compiled client code (the application using pthreads -> involvement of | ||
| "pthread.h"). | "pthread.h"). | ||
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| I think the message of this section is that usage of VCE version of pthreads | 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 | in applications relying on cancellation/cleanup AND using optimisations for | ||
| creation of production code is highly unreliable for the current version of | creation of production code is highly unreliable for the current version of | ||
| the pthreads library. | the pthreads library. | ||
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