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NEWS
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CURRENT CVS HEAD Version
RELEASE 2.9.0 pending
-------------
(2010-??-??)
General
-------
New bug fixes in this release since 2.8.0 have NOT been applied to the
1.x.x series.
Version 1 no longer maintained
------------------------------
The 1.x.x series is no longer maintained. However, if you really need a
version 1, the differences between 1.11.0 and 2.7.0 are very small, mainly
revolving around the pthread_once_t_ struct. Those differences applied
as a patch to the current 2.x.x should work. Don't forget to change
the version numbering in pthread.h before building. If you distribute
such a version 1.x.x please bear in mind that your numbers may clash
with those of others doing the same thing. Please consider also making
identifying changes in version.rc to differentiate your build.
Testing and verification
------------------------
The current CVS head version has been tested on an SMP architecture
(AMD Phenom 9750 Quad Core) by running the MinGW32 (GCC) builds against
the full test suite, stress tests and benchmarks.
New Features
------------
Dependence on the winsock library is now discretionary via
#define RETAIN_WSALASTERROR in config.h. It is undefined by default unless
WINCE is defined (because I (RJ) am unsure of the dependency there).
- Ramiro Polla
(MSC and GNU builds) The statically linked library now automatically
initialises and cleans up on program start/exit, i.e. statically linked
applications need not call the routines pthread_win32_process_attach_np()
and pthread_win32_process_detach_np() explicitly. The per-thread routine
pthread_win32_thread_detach_np() is also called at program exit to cleanup
POSIX resources acquired by the primary Windows native thread (if I (RJ)
understand the process correctly). Other Windows native threads that call
POSIX API routines may need to call the thread detach routine on thread
exit if the application depends on reclaimed POSIX resources or running
POSIX TSD (TLS) destructors.
See README.NONPORTABLE for descriptions of these routines.
- Ramiro Polla
Bug fixes
---------
Various modifications and fixes to build and test for WinCE.
- Marcel Ruff, Sinan Kaya
Fix pthread_cond_destroy() - should not be a cancellation point. Other
minor build problems fixed.
- Romano Paolo Tenca
Remove potential deadlock condition from pthread_cond_destroy().
- Eric Berge
Various modifications to build and test for Win64.
- Kip Streithorst
Various fixes to the QueueUserAPCEx async cancellation helper DLL
(this is a separate download) and pthreads code cleanups.
- Sebastian Gottschalk
Removed potential NULL pointer reference.
- Robert Kindred
Removed the requirement that applications restrict the number of threads
calling pthread_barrier_wait() [on the same barrier] to just the barrier
count in order to avoid contention and dead lock. Also reduced the
contention between barrier_wait and barrier_destroy. This change will
have slowed barriers down slightly but halves the number of semaphores
consumed per barrier to one.
- Ross Johnson
RELEASE 2.8.0
-------------
(2006-12-22)
General
-------
New bug fixes in this release since 2.7.0 have not been applied to the
version 1.x.x series. It is probably time to drop version 1.
Testing and verification
------------------------
This release has not yet been tested on SMP architechtures. All tests pass
on a uni-processor system.
Bug fixes
---------
Sem_destroy could return EBUSY even though no threads were waiting on the
semaphore. Other races around invalidating semaphore structs (internally)
have been removed as well.
New tests
---------
semaphore5.c - tests the bug fix referred to above.
RELEASE 2.7.0
-------------
(2005-06-04)
General
-------
All new features in this release have been back-ported in release 1.11.0,
including the incorporation of MCS locks in pthread_once, however, versions
1 and 2 remain incompatible even though they are now identical in
performance and functionality.
Testing and verification
------------------------
This release has been tested (passed the test suite) on both uni-processor
and multi-processor systems.
- Tim Theisen
Bug fixes
---------
Pthread_once has been re-implemented to remove priority boosting and other
complexity to improve robustness. Races for Win32 handles that are not
recycle-unique have been removed. The general form of pthread_once is now
the same as that suggested earlier by Alexander Terekhov, but instead of the
'named mutex', a queue-based lock has been implemented which has the required
properties of dynamic self initialisation and destruction. This lock is also
efficient. The ABI is unaffected in as much as the size of pthread_once_t has
not changed and PTHREAD_ONCE_INIT has not changed, however, applications that
peek inside pthread_once_t, which is supposed to be opaque, will break.
- Vladimir Kliatchko
New features
------------
* Support for Mingw cross development tools added to GNUmakefile.
Mingw cross tools allow building the libraries on Linux.
- Mikael Magnusson
RELEASE 2.6.0
-------------
(2005-05-19)
General
-------
All of the bug fixes and new features in this release have been
back-ported in release 1.10.0.
Testing and verification
------------------------
This release has been tested (passed the test suite) on both uni-processor
and multi-processor systems. Thanks to Tim Theisen at TomoTherapy for
exhaustively running the MP tests and for providing crutial observations
and data when faults are detected.
Bugs fixed
----------
* pthread_detach() now reclaims remaining thread resources if called after
the target thread has terminated. Previously, this routine did nothing in
this case.
New tests
---------
* detach1.c - tests that pthread_detach properly invalidates the target
thread, which indicates that the thread resources have been reclaimed.
RELEASE 2.5.0
-------------
(2005-05-09)
General
-------
The package now includes a reference documentation set consisting of
HTML formatted Unix-style manual pages that have been edited for
consistency with Pthreads-w32. The set can also be read online at:
http://sources.redhat.com/pthreads-win32/manual/index.html
Thanks again to Tim Theisen for running the test suite pre-release
on an MP system.
All of the bug fixes and new features in this release have been
back-ported in release 1.9.0.
Bugs fixed
----------
* Thread Specific Data (TSD) key management has been ammended to
eliminate a source of (what was effectively) resource leakage (a HANDLE
plus memory for each key destruct routine/thread association). This was
not a true leak because these resources were eventually reclaimed when
pthread_key_delete was run AND each thread referencing the key had exited.
The problem was that these two conditions are often not met until very
late, and often not until the process is about to exit.
The ammended implementation avoids the need for the problematic HANDLE
and reclaims the memory as soon as either the key is deleted OR the
thread exits, whichever is first.
Thanks to Richard Hughes at Aculab for identifying and locating the leak.
* TSD key destructors are now processed up to PTHREAD_DESTRUCTOR_ITERATIONS
times instead of just once. PTHREAD_DESTRUCTOR_ITERATIONS has been
defined in pthread.h for some time but not used.
* Fix a semaphore accounting race between sem_post/sem_post_multiple
and sem_wait cancellation. This is the same issue as with
sem_timedwait that was fixed in the last release.
* sem_init, sem_post, and sem_post_multiple now check that the
semaphore count never exceeds _POSIX_SEM_VALUE_MAX.
* Although sigwait() is nothing more than a no-op, it should at least
be a cancellation point to be consistent with the standard.
New tests
---------
* stress1.c - attempts to expose problems in condition variable
and semaphore timed wait logic. This test was inspired by Stephan
Mueller's sample test code used to identify the sem_timedwait bug
from the last release. It's not a part of the regular test suite
because it can take awhile to run. To run it:
nmake clean VC-stress
* tsd2.c - tests that key destructors are re-run if the tsd key value is
not NULL after the destructor routine has run. Also tests that
pthread_setspecific() and pthread_getspecific() are callable from
destructors.
RELEASE 2.4.0
-------------
(2005-04-26)
General
-------
There is now no plan to release a version 3.0.0 to fix problems in
pthread_once(). Other possible implementations of pthread_once
will still be investigated for a possible future release in an attempt
to reduce the current implementation's complexity.
All of the bug fixes and new features in this release have been
back-ported for release 1.8.0.
Bugs fixed
----------
* Fixed pthread_once race (failures on an MP system). Thanks to
Tim Theisen for running exhaustive pre-release testing on his MP system
using a range of compilers:
VC++ 6
VC++ 7.1
Intel C++ version 8.0
All tests passed.
Some minor speed improvements were also done.
* Fix integer overrun error in pthread_mutex_timedlock() - missed when
sem_timedwait() was fixed in release 2.2.0. This routine no longer returns
ENOTSUP when NEED_SEM is defined - it is supported (NEED_SEM is only
required for WinCE versions prior to 3.0).
* Fix timeout bug in sem_timedwait().
- Thanks to Stephan Mueller for reporting, providing diagnostic output
and test code.
* Fix several problems in the NEED_SEM conditionally included code.
NEED_SEM included code is provided for systems that don't implement W32
semaphores, such as WinCE prior to version 3.0. An alternate implementation
of POSIX semaphores is built using W32 events for these systems when
NEED_SEM is defined. This code has been completely rewritten in this
release to reuse most of the default POSIX semaphore code, and particularly,
to implement all of the sem_* routines supported by pthreads-win32. Tim
Theisen also run the test suite over the NEED_SEM code on his MP system. All
tests passed.
* The library now builds without errors for the Borland Builder 5.5 compiler.
New features
------------
* pthread_mutex_timedlock() and all sem_* routines provided by
pthreads-win32 are now implemented for WinCE versions prior to 3.0. Those
versions did not implement W32 semaphores. Define NEED_SEM in config.h when
building the library for these systems.
Known issues in this release
----------------------------
* pthread_once is too complicated - but it works as far as testing can
determine..
* The Borland version of the dll fails some of the tests with a memory read
exception. The cause is not yet known but a compiler bug has not been ruled
out.
RELEASE 2.3.0
-------------
(2005-04-12)
General
-------
Release 1.7.0 is a backport of features and bug fixes new in
this release. See earlier notes under Release 2.0.0/General.
Bugs fixed
----------
* Fixed pthread_once potential for post once_routine cancellation
hanging due to starvation. See comments in pthread_once.c.
Momentary priority boosting is used to ensure that, after a
once_routine is cancelled, the thread that will run the
once_routine is not starved by higher priority waiting threads at
critical times. Priority boosting occurs only AFTER a once_routine
cancellation, and is applied only to that once_control. The
once_routine is run at the thread's normal base priority.
New tests
---------
* once4.c: Aggressively tests pthread_once() under realtime
conditions using threads with varying priorities. Windows'
random priority boosting does not occur for threads with realtime
priority levels.
RELEASE 2.2.0
-------------
(2005-04-04)
General
-------
* Added makefile targets to build static link versions of the library.
Both MinGW and MSVC. Please note that this does not imply any change
to the LGPL licensing, which still imposes psecific conditions on
distributing software that has been statically linked with this library.
* There is a known bug in pthread_once(). Cancellation of the init_routine
exposes a potential starvation (i.e. deadlock) problem if a waiting thread
has a higher priority than the initting thread. This problem will be fixed
in version 3.0.0 of the library.
Bugs fixed
----------
* Fix integer overrun error in sem_timedwait().
Kevin Lussier
* Fix preprocessor directives for static linking.
Dimitar Panayotov
RELEASE 2.1.0
-------------
(2005-03-16)
Bugs fixed
----------
* Reverse change to pthread_setcancelstate() in 2.0.0.
RELEASE 2.0.0
-------------
(2005-03-16)
General
-------
This release represents an ABI change and the DLL version naming has
incremented from 1 to 2, e.g. pthreadVC2.dll.
Version 1.4.0 back-ports the new functionality included in this
release. Please distribute DLLs built from that version with updates
to applications built on pthreads-win32 version 1.x.x.
The package naming has changed, replacing the snapshot date with
the version number + descriptive information. E.g. this
release is "pthreads-w32-2-0-0-release".
Bugs fixed
----------
* pthread_setcancelstate() no longer checks for a pending
async cancel event if the library is using alertable async
cancel. See the README file (Prerequisites section) for info
on adding alertable async cancelation.
New features
------------
* pthread_once() now supports init_routine cancellability.
New tests
---------
* Agressively test pthread_once() init_routine cancellability.
SNAPSHOT 2005-03-08
-------------------
Version 1.3.0
Bug reports (fixed)
-------------------
* Implicitly created threads leave Win32 handles behind after exiting.
- Dmitrii Semii
* pthread_once() starvation problem.
- Gottlob Frege
New tests
---------
* More intense testing of pthread_once().
SNAPSHOT 2005-01-25
-------------------
Version 1.2.0
Bug fixes
---------
* Attempted acquisition of a recursive mutex could cause waiting threads
to not be woken when the mutex was released.
- Ralf Kubis <RKubis at mc.com>
* Various package omissions have been fixed.
SNAPSHOT 2005-01-03
-------------------
Version 1.1.0
Bug fixes
---------
* Unlocking recursive or errorcheck mutexes would sometimes
unexpectedly return an EPERM error (bug introduced in
snapshot-2004-11-03).
- Konstantin Voronkov <beowinkle at yahoo.com>
SNAPSHOT 2004-11-22
-------------------
Version 1.0.0
This snapshot primarily fixes the condvar bug introduced in
snapshot-2004-11-03. DLL versioning has also been included to allow
applications to runtime check the Microsoft compatible DLL version
information, and to extend the DLL naming system for ABI and major
(non-backward compatible) API changes. See the README file for details.
Bug fixes
---------
* Condition variables no longer deadlock (bug introduced in
snapshot-2004-11-03).
- Alexander Kotliarov and Nicolas at saintmac
* DLL naming extended to avoid 'DLL hell' in the future, and to
accommodate the ABI change introduced in snapshot-2004-11-03. Snapshot
2004-11-03 will be removed from FTP sites.
New features
------------
* A Microsoft-style version resource has been added to the DLL for
applications that wish to check DLL compatibility at runtime.
* Pthreads-win32 DLL naming has been extended to allow incompatible DLL
versions to co-exist in the same filesystem. See the README file for details,
but briefly: while the version information inside the DLL will change with
each release from now on, the DLL version names will only change if the new
DLL is not backward compatible with older applications.
The versioning scheme has been borrowed from GNU Libtool, and the DLL
naming scheme is from Cygwin. Provided the Libtool-style numbering rules are
honoured, the Cygwin DLL naming scheme automatcally ensures that DLL name
changes are minimal and that applications will not load an incompatible
pthreads-win32 DLL.
Those who use the pre-built DLLs will find that the DLL/LIB names have a new
suffix (1) in this snapshot. E.g. pthreadVC1.dll etc.
* The POSIX thread ID reuse uniqueness feature introduced in the last snapshot
has been kept as default, but the behaviour can now be controlled when the DLL
is built to effectively switch it off. This makes the library much more
sensitive to applications that assume that POSIX thread IDs are unique, i.e.
are not strictly compliant with POSIX. See the PTW32_THREAD_ID_REUSE_INCREMENT
macro comments in config.h for details.
Other changes
-------------
Certain POSIX macros have changed.
These changes are intended to conform to the Single Unix Specification version 3,
which states that, if set to 0 (zero) or not defined, then applications may use
sysconf() to determine their values at runtime. Pthreads-win32 does not
implement sysconf().
The following macros are no longer undefined, but defined and set to -1
(not implemented):
_POSIX_THREAD_ATTR_STACKADDR
_POSIX_THREAD_PRIO_INHERIT
_POSIX_THREAD_PRIO_PROTECT
_POSIX_THREAD_PROCESS_SHARED
The following macros are defined and set to 200112L (implemented):
_POSIX_THREADS
_POSIX_THREAD_SAFE_FUNCTIONS
_POSIX_THREAD_ATTR_STACKSIZE
_POSIX_THREAD_PRIORITY_SCHEDULING
_POSIX_SEMAPHORES
_POSIX_READER_WRITER_LOCKS
_POSIX_SPIN_LOCKS
_POSIX_BARRIERS
The following macros are defined and set to appropriate values:
_POSIX_THREAD_THREADS_MAX
_POSIX_SEM_VALUE_MAX
_POSIX_SEM_NSEMS_MAX
PTHREAD_DESTRUCTOR_ITERATIONS
PTHREAD_KEYS_MAX
PTHREAD_STACK_MIN
PTHREAD_THREADS_MAX
SNAPSHOT 2004-11-03
-------------------
DLLs produced from this snapshot cannot be used with older applications without
recompiling the application, due to a change to pthread_t to provide unique POSIX
thread IDs.
Although this snapshot passes the extended test suite, many of the changes are
fairly major, and some applications may show different behaviour than previously,
so adopt with care. Hopefully, any changed behaviour will be due to the library
being better at it's job, not worse.
Bug fixes
---------
* pthread_create() no longer accepts NULL as the thread reference arg.
A segfault (memory access fault) will result, and no thread will be
created.
* pthread_barrier_wait() no longer acts as a cancelation point.
* Fix potential race condition in pthread_once()
- Tristan Savatier <tristan at mpegtv.com>
* Changes to pthread_cond_destroy() exposed some coding weaknesses in several
test suite mini-apps because pthread_cond_destroy() now returns EBUSY if the CV
is still in use.
New features
------------
* Added for compatibility:
PTHREAD_RECURSIVE_MUTEX_INITIALIZER,
PTHREAD_ERRORCHECK_MUTEX_INITIALIZER,
PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP,
PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP
* Initial support for Digital Mars compiler
- Anuj Goyal <anuj.goyal at gmail.com>
* Faster Mutexes. These have been been rewritten following a model provided by
Alexander Terekhov that reduces kernel space checks, and eliminates some additional
critical sections used to manage a race between timedlock expiration and unlock.
Please be aware that the new mutexes do not enforce strict absolute FIFO scheduling
of mutexes, however any out-of-order lock acquisition should be very rare.
* Faster semaphores. Following a similar model to mutexes above, these have been
rewritten to use preliminary users space checks.
* sem_getvalue() now returns the number of waiters.
* The POSIX thread ID now has much stronger uniqueness characteristics. The library
garrantees not to reuse the same thread ID for at least 2^(wordsize) thread
destruction/creation cycles.
New tests
---------
* semaphore4.c: Tests cancelation of the new sem_wait().
* semaphore4t.c: Likewise for sem_timedwait().
* rwlock8.c: Tests and times the slow execution paths of r/w locks, and the CVs,
mutexes, and semaphores that they're built on.
SNAPSHOT 2004-05-16
-------------------
Attempt to add Watcom to the list of compilers that can build the library.
This failed in the end due to it's non-thread-aware errno. The library
builds but the test suite fails. See README.Watcom for more details.
Bug fixes
---------
* Bug and memory leak in sem_init()
- Alex Blanco <Alex.Blanco at motorola.com>
* ptw32_getprocessors() now returns CPU count of 1 for WinCE.
- James Ewing <james.ewing at sveasoft.com>
* pthread_cond_wait() could be canceled at a point where it should not
be cancelable. Fixed.
- Alexander Terekhov <TEREKHOV at de.ibm.com>
* sem_timedwait() had an incorrect timeout calculation.
- Philippe Di Cristo <philipped at voicebox.com>
* Fix a memory leak left behind after threads are destroyed.
- P. van Bruggen <pietvb at newbridges.nl>
New features
------------
* Ported to AMD64.
- Makoto Kato <raven at oldskool.jp>
* True pre-emptive asynchronous cancelation of threads. This is optional
and requires that Panagiotis E. Hadjidoukas's QueueUserAPCEx package be
installed. This package is included in the pthreads-win32 self-unpacking
Zip archive starting from this snapshot. See the README.txt file inside
the package for installation details.
Note: If you don't use async cancelation in your application, or don't need
to cancel threads that are blocked on system resources such as network I/O,
then the default non-preemptive async cancelation is probably good enough.
However, pthreads-win32 auto-detects the availability of these components
at run-time, so you don't need to rebuild the library from source if you
change your mind later.
All of the advice available in books and elsewhere on the undesirability
of using async cancelation in any application still stands, but this
feature is a welcome addition with respect to the library's conformance to
the POSIX standard.
SNAPSHOT 2003-09-18
-------------------
Cleanup of thread priority management. In particular, setting of thread
priority now attempts to map invalid Win32 values within the range returned
by sched_get_priority_min/max() to useful values. See README.NONPORTABLE
under "Thread priority".
Bug fixes
---------
* pthread_getschedparam() now returns the priority given by the most recent
call to pthread_setschedparam() or established by pthread_create(), as
required by the standard. Previously, pthread_getschedparam() incorrectly
returned the running thread priority at the time of the call, which may have
been adjusted or temporarily promoted/demoted.
* sched_get_priority_min() and sched_get_priority_max() now return -1 on error
and set errno. Previously, they incorrectly returned the error value directly.
SNAPSHOT 2003-09-04
-------------------
Bug fixes
---------
* ptw32_cancelableWait() now allows cancelation of waiting implicit POSIX
threads.
New test
--------
* cancel8.c tests cancelation of Win32 threads waiting at a POSIX cancelation
point.
SNAPSHOT 2003-09-03
-------------------
Bug fixes
---------
* pthread_self() would free the newly created implicit POSIX thread handle if
DuplicateHandle failed instead of recycle it (very unlikely).
* pthread_exit() was neither freeing nor recycling the POSIX thread struct
for implicit POSIX threads.
New feature - Cancelation of/by Win32 (non-POSIX) threads
---------------------------------------------------------
Since John Bossom's original implementation, the library has allowed non-POSIX
initialised threads (Win32 threads) to call pthreads-win32 routines and
therefore interact with POSIX threads. This is done by creating an on-the-fly
POSIX thread ID for the Win32 thread that, once created, allows fully
reciprical interaction. This did not extend to thread cancelation (async or
deferred). Now it does.
Any thread can be canceled by any other thread (Win32 or POSIX) if the former
thread's POSIX pthread_t value is known. It's TSD destructors and POSIX
cleanup handlers will be run before the thread exits with an exit code of
PTHREAD_CANCELED (retrieved with GetExitCodeThread()).
This allows a Win32 thread to, for example, call POSIX CV routines in the same way
that POSIX threads would/should, with pthread_cond_wait() cancelability and
cleanup handlers (pthread_cond_wait() is a POSIX cancelation point).
By adding cancelation, Win32 threads should now be able to call all POSIX
threads routines that make sense including semaphores, mutexes, condition
variables, read/write locks, barriers, spinlocks, tsd, cleanup push/pop,
cancelation, pthread_exit, scheduling, etc.
Note that these on-the-fly 'implicit' POSIX thread IDs are initialised as detached
(not joinable) with deferred cancelation type. The POSIX thread ID will be created
automatically by any POSIX routines that need a POSIX handle (unless the routine
needs a pthread_t as a parameter of course). A Win32 thread can discover it's own
POSIX thread ID by calling pthread_self(), which will create the handle if
necessary and return the pthread_t value.
New tests
---------
Test the above new feature.
SNAPSHOT 2003-08-19
-------------------
This snapshot fixes some accidental corruption to new test case sources.
There are no changes to the library source code.
SNAPSHOT 2003-08-15
-------------------
Bug fixes
---------
* pthread.dsp now uses correct compile flags (/MD).
- Viv <[email protected]>
* pthread_win32_process_detach_np() fixed memory leak.
- Steven Reddie <[email protected]>
* pthread_mutex_destroy() fixed incorrect return code.
- Nicolas Barry <[email protected]>
* pthread_spin_destroy() fixed memory leak.
- Piet van Bruggen <[email protected]>
* Various changes to tighten arg checking, and to work with later versions of
MinGW32 and MsysDTK.
* pthread_getschedparam() etc, fixed dangerous thread validity checking.
- Nicolas Barry <[email protected]>
* POSIX thread handles are now reused and their memory is not freed on thread exit.
This allows for stronger thread validity checking.
New standard routine
--------------------
* pthread_kill() added to provide thread validity checking to applications.
It does not accept any non zero values for the signal arg.
New test cases
--------------
* New test cases to confirm validity checking, pthread_kill(), and thread reuse.
SNAPSHOT 2003-05-10
-------------------
Bug fixes
---------
* pthread_mutex_trylock() now returns correct error values.
pthread_mutex_destroy() will no longer destroy a recursively locked mutex.
pthread_mutex_lock() is no longer inadvertantly behaving as a cancelation point.
- Thomas Pfaff <[email protected]>
* pthread_mutex_timedlock() no longer occasionally sets incorrect mutex
ownership, causing deadlocks in some applications.
- Robert Strycek <[email protected]> and Alexander Terekhov <[email protected]>
SNAPSHOT 2002-11-04
-------------------
Bug fixes
---------
* sem_getvalue() now returns the correct value under Win NT and WinCE.
- Rob Fanner <[email protected]>
* sem_timedwait() now uses tighter checks for unreasonable
abstime values - that would result in unexpected timeout values.
* ptw32_cond_wait_cleanup() no longer mysteriously consumes
CV signals but may produce more spurious wakeups. It is believed
that the sem_timedwait() call is consuming a CV signal that it
shouldn't.
- Alexander Terekhov <[email protected]>
* Fixed a memory leak in ptw32_threadDestroy() for implicit threads.
* Fixed potential for deadlock in pthread_cond_destroy().
A deadlock could occur for statically declared CVs (PTHREAD_COND_INITIALIZER),
when one thread is attempting to destroy the condition variable while another
is attempting to dynamically initialize it.
- Michael Johnson <[email protected]>
SNAPSHOT 2002-03-02
-------------------
Cleanup code default style. (IMPORTANT)
----------------------------------------------------------------------
Previously, if not defined, the cleanup style was determined automatically
from the compiler/language, and one of the following was defined accordingly:
__CLEANUP_SEH MSVC only
__CLEANUP_CXX C++, including MSVC++, GNU G++
__CLEANUP_C C, including GNU GCC, not MSVC
These defines determine the style of cleanup (see pthread.h) and,
most importantly, the way that cancelation and thread exit (via
pthread_exit) is performed (see the routine ptw32_throw() in private.c).
In short, the exceptions versions of the library throw an exception
when a thread is canceled or exits (via pthread_exit()), which is
caught by a handler in the thread startup routine, so that the
the correct stack unwinding occurs regardless of where the thread
is when it's canceled or exits via pthread_exit().
In this and future snapshots, unless the build explicitly defines (e.g.
via a compiler option) __CLEANUP_SEH, __CLEANUP_CXX, or __CLEANUP_C, then
the build NOW always defaults to __CLEANUP_C style cleanup. This style
uses setjmp/longjmp in the cancelation and pthread_exit implementations,
and therefore won't do stack unwinding even when linked to applications
that have it (e.g. C++ apps). This is for consistency with most
current commercial Unix POSIX threads implementations. Compaq's TRU64
may be an exception (no pun intended) and possible future trend.
Although it was not clearly documented before, it is still necessary to
build your application using the same __CLEANUP_* define as was
used for the version of the library that you link with, so that the
correct parts of pthread.h are included. That is, the possible
defines require the following library versions:
__CLEANUP_SEH pthreadVSE.dll
__CLEANUP_CXX pthreadVCE.dll or pthreadGCE.dll
__CLEANUP_C pthreadVC.dll or pthreadGC.dll
E.g. regardless of whether your app is C or C++, if you link with
pthreadVC.lib or libpthreadGC.a, then you must define __CLEANUP_C.
THE POINT OF ALL THIS IS: if you have not been defining one of these
explicitly, then the defaults as described at the top of this
section were being used.
THIS NOW CHANGES, as has been explained above, but to try to make this
clearer here's an example:
If you were building your application with MSVC++ i.e. using C++
exceptions and not explicitly defining one of __CLEANUP_*, then
__CLEANUP_C++ was automatically defined for you in pthread.h.
You should have been linking with pthreadVCE.dll, which does
stack unwinding.
If you now build your application as you had before, pthread.h will now
automatically set __CLEANUP_C as the default style, and you will need to
link with pthreadVC.dll. Stack unwinding will now NOT occur when a thread
is canceled, or the thread calls pthread_exit().
Your application will now most likely behave differently to previous
versions, and in non-obvious ways. Most likely is that locally
instantiated objects may not be destroyed or cleaned up after a thread
is canceled.
If you want the same behaviour as before, then you must now define
__CLEANUP_C++ explicitly using a compiler option and link with
pthreadVCE.dll as you did before.
WHY ARE WE MAKING THE DEFAULT STYLE LESS EXCEPTION-FRIENDLY?
Because no commercial Unix POSIX threads implementation allows you to
choose to have stack unwinding. Therefore, providing it in pthread-win32
as a default is dangerous. We still provide the choice but unless
you consciously choose to do otherwise, your pthreads applications will
now run or crash in similar ways irrespective of the threads platform
you use. Or at least this is the hope.
WHY NOT REMOVE THE EXCEPTIONS VERSIONS OF THE LIBRARY ALTOGETHER?
There are a few reasons:
- because there are well respected POSIX threads people who believe
that POSIX threads implementations should be exceptions aware and
do the expected thing in that context. (There are equally respected
people who believe it should not be easily accessible, if it's there
at all, for unconditional conformity to other implementations.)
- because pthreads-win32 is one of the few implementations that has
the choice, perhaps the only freely available one, and so offers
a laboratory to people who may want to explore the effects;
- although the code will always be around somewhere for anyone who
wants it, once it's removed from the current version it will not be
nearly as visible to people who may have a use for it.
Source module splitting
-----------------------
In order to enable smaller image sizes to be generated
for applications that link statically with the library,
most routines have been separated out into individual
source code files.
This is being done in such a way as to be backward compatible.
The old source files are reused to congregate the individual
routine files into larger translation units (via a bunch of
# includes) so that the compiler can still optimise wherever
possible, e.g. through inlining, which can only be done
within the same translation unit.
It is also possible to build the entire library by compiling
the single file named "pthread.c", which just #includes all
the secondary congregation source files. The compiler
may be able to use this to do more inlining of routines.
Although the GNU compiler is able to produce libraries with
the necessary separation (the -ffunction-segments switch),
AFAIK, the MSVC and other compilers don't have this feature.
Finally, since I use makefiles and command-line compilation,
I don't know what havoc this reorganisation may wreak amongst
IDE project file users. You should be able to continue
using your existing project files without modification.
New non-portable functions
--------------------------
pthread_num_processors_np():
Returns the number of processors in the system that are
available to the process, as determined from the processor
affinity mask.
pthread_timechange_handler_np():
To improve tolerance against operator or time service initiated
system clock changes.
This routine can be called by an application when it
receives a WM_TIMECHANGE message from the system. At present
it broadcasts all condition variables so that waiting threads
can wake up and re-evaluate their conditions and restart
their timed waits if required.
- Suggested by Alexander Terekhov
Platform dependence
-------------------
As Win95 doesn't provide one, the library now contains
it's own InterlockedCompareExchange() routine, which is used
whenever Windows doesn't provide it. InterlockedCompareExchange()
is used to implement spinlocks and barriers, and also in mutexes.
This routine relies on the CMPXCHG machine instruction which
is not available on i386 CPUs. This library (from snapshot
20010712 onwards) is therefore no longer supported on i386
processor platforms.
New standard routines
---------------------
For source code portability only - rwlocks cannot be process shared yet.
pthread_rwlockattr_init()
pthread_rwlockattr_destroy()
pthread_rwlockattr_setpshared()
pthread_rwlockattr_getpshared()
As defined in the new POSIX standard, and the Single Unix Spec version 3:
sem_timedwait()
pthread_mutex_timedlock() - Alexander Terekhov and Thomas Pfaff
pthread_rwlock_timedrdlock() - adapted from pthread_rwlock_rdlock()
pthread_rwlock_timedwrlock() - adapted from pthread_rwlock_wrlock()
pthread.h no longer includes windows.h
--------------------------------------
[Not yet for G++]