path: root/README

PTHREADS-WIN32
==============

Pthreads-win32 is free software, distributed under the GNU Library
General Public License (LGPL). See the file 'COPYING.LIB' for terms
and conditions.


What is it?
-----------

Pthreads-win32 is an Open Source Software (OSS) implementation of the
Threads component of the POSIX 1003.1c 1995 Standard for Microsoft's
Win32 environment. Some functions from POSIX 1003.1b are also
supported including semaphores. Other related functions include
the set of read-write lock functions.

See the file "ANNOUNCE" for more information including standards
conformance details and list of supported routines.


Library naming
--------------

Because the library is being built using various exception
handling schemes and compilers - and because the library
will not work reliably if these are mixed in an application,
each different version of the library has it's own name.

In general:
	pthread[VG][SC]E.dll
	pthread[VG][SC]E.lib

where:
	[VG] indicates the compiler
	V	- MS VC++
	G	- GNU G++

	[SC] indicates the exception handling scheme
	S	- Structured EH
	C	- C++ EH

For example:
	pthreadVSE.dll	(VC++/SEH)
	pthreadGCE.dll	(G++/C++ EH)

The GNU library archive file name has changed to:

	libpthreadw32.a	(the "32" is now "w32")


Other name changes
------------------

All snapshots prior to and including snapshot 2000-08-13
used "_pthread_" as the prefix to library internal
functions, and "_PTHREAD_" to many library internal
macros. These have now been changed to "ptw32_" and "PTW32_"
respectively so as to not conflict with the ANSI standard's
reservation of identifiers beginning with "_" and "__" for
use by compiler implementations only.

If you have written any applications and you are linking
statically with the pthreads-win32 library then you may have
included a call to _pthread_processInitialize. You will
now have to change that to ptw32_processInitialize.


Known bugs in this snapshot
---------------------------

1. Asynchronous cancelation only works on Intel X86 machines.

2. Running the test "join1.c" with the library built with Mingw32
and the GNUmakefile included, the test fails with a segmentation (invalid
page access) exception. The fault appears to be in the assembler code
emmitted by the compiler [to handle exception contexts] at the
end of the try block in ptw32_threadStart().

3. There are problems using the libpthreadw32.a stub archive derived
from either of pthreadVSE.dll or pthreadVCE.dll. The cleanup1.c test
fails. This is now an expected result of having different EH and cleanup
handler schemes in the library and application.


Caveats
-------

1. Due to what is believed to be C++ compliance error in VC++,
if your application contains catch(...) blocks in your POSIX threads
then you will need to replace the "catch(...)" with the macro
"PtW32Catch", eg.

	#ifdef PtW32Catch
		PtW32Catch {
			...
		}
	#else
		catch(...) {
			...
		}
	#endif

Otherwise neither pthreads cancelation nor pthread_exit() will work
reliably.


Non-portable functions included in the library
----------------------------------------------

void
pthread_mutexattr_setforcecs_np(pthread_mutexattr_t *attr,
				int forcecs);

	Allows an application to force the library to use
	critical sections rather than win32 mutexes as
	the basis for any mutex that uses "attr".
	Critical sections are significantly faster than
	mutexes.

	Values for "forcecs" are:
	PTHREAD_MUTEX_AUTO_CS_NP
		- allow the library to decide based on
		  availability of tryEnterCriticalSection().
		  The library determines this at runtime
		  and will use critical sections whenever
		  tryEnterCriticalSection() is available.
	PTHREAD_MUTEX_FORCE_CS_NP
		- force use of critical sections even if
		  tryEnterCriticalSection() isn't provided
		  by the system, but you'd better not try
		  to use pthread_mutex_trylock() on any
		  mutex that uses "attr" if you want your
		  application to work on all versions of
		  Windows.

HANDLE
pthread_getw32threadhandle_np(pthread_t thread);

	Returns the win32 thread handle that the POSIX
	thread "thread" is running as.

	Applications can use the win32 handle to set
	win32 specific attributes of the thread.

int
pthreadCancelableWait (HANDLE waitHandle);

int
pthreadCancelableTimedWait (HANDLE waitHandle, DWORD timeout);

	These two functions provide hooks into the pthread_cancel
	mechanism that will allow you to wait on a Windows handle
	and make it a cancellation point. Both functions block
	until either the given w32 handle is signaled, or
	pthread_cancel has been called. It is implemented using
	WaitForMultipleObjects on 'waitHandle' and a manually
	reset w32 event used to implement pthread_cancel.
 

Building under VC++ using either C++ EH or Structured EH
--------------------------------------------------------

From the source directory run one of the following:

nmake clean VCE	(builds the VC++ C++ EH version pthreadVCE.dll)

or:

nmake clean VSE	(builds the VC++ structured EH version pthreadVSE.dll)

You can run the testsuite by changing to the "tests" directory and
running the target corresponding to the DLL version you built:

nmake clean VCE

or:

nmake clean VSE


Building under Mingw32
----------------------

The dll can be built with Mingw32 gcc-2.95.2 or later.
Run "make" in the source directory (uses GNUmakefile). This builds
pthreadGCE.dll and libpthreadw32.a.

To generate the libpthreadw32.a file from pthreadVCE.dll rather than
building the library with G++, run "make fake.a". (You must have
pthreadVCE.dll already built - see above.)
Please note that VC++ and GNU exception handling is implemented
completely differently and so automatic cleanup of objects and
the propagation of exceptions themselves between the two schemes is not
going to happen.

You can run the testsuite by changing to the "tests" directory and
running "make clean" and then "make". See the "Known bugs" section above.


Building the library under Cygwin
---------------------------------

Not tested by me although I think some people have done this.
Not sure how successfully though.

Cygwin is implementing it's own POSIX threads routines and these
will be the ones to use if you develop using Cygwin.


Ready to run binaries
---------------------

For convenience, the following ready-to-run files can be downloaded
from the FTP site (see under "Availability" below):

	pthread.h
	semaphore.h
	sched.h
	pthread.def
	pthreadVCE.dll	- built with MSVC++ compiler using C++ EH
	pthreadVCE.lib
	pthreadVSE.dll	- built with MSVC++ compiler using SEH
	pthreadVSE.lib
	pthreadGCE.dll	- built with Mingw32 G++ (see "Known Bugs")
	libpthreadw32.a	- derived from pthreadGCE.dll


Building applications with the library
--------------------------------------

Use the appropriate DLL and LIB files to match the exception handing
that you use in your application, or specifically, in your POSIX
threads. Don't mix them or neither thread cancelation nor
pthread_exit() will work reliably if at all.


Building applications with GNU compilers
----------------------------------------

[Please see the section on Known Bugs above and the section
dealing with building the library with Mingw32 before
you build applications using the GNU compilers. Please also
note that the pre-built pthreadGCE.dll is currently only
a copy of the dll built by MSVC++. Note that VC++ and
GNU exception handling is implemented completely differently
and so automatic cleanup of objects and the propagation of
exceptions themselves between the two schemes is not
going to happen. You'll need to wait for the version of
pthreadGCE.dll built be G++ itself which still has problems.]

Use gcc-2.95.2 or later.

With pthreadGCE.dll and libpthreadw32.a in the same directory as your
application myapp.c, you could compile, link and run myapp.c under
Mingw32 as follows:

	gcc -x c++ -o myapp.exe myapp.c -I. -L. -lpthreadw32
	myapp

Or put pthreadGCE.dll in an appropriate directory in your PATH,
put libpthread32.a in MINGW_ROOT\i386-mingw32\lib, and
put pthread.h in MINGW_ROOT\i386-mingw32\include, then use:

	gcc -x c++ -o myapp.exe myapp.c -lpthreadw32
	myapp


Availability
------------

The complete source code in either unbundled, self-extracting
Zip file, or tar/gzipped format can be found at:

	ftp://sources.redhat.com/pub/pthreads-win32

The pre-built DLL, export libraries and matching pthread.h can
be found at:

	ftp://sources.redhat.com/pub/pthreads-win32/dll-latest

Home page:

	http://sources.redhat.com/pthreads-win32/


Mailing list
------------

There is a mailing list for discussing pthreads on Win32.
To join, send email to:

	pthreads-win32-subscribe@sources.redhat.com

Unsubscribe by sending mail to:

	pthreads-win32-unsubscribe@sources.redhat.com


Acknowledgements
----------------

Pthreads-win32 is based substantially on a Win32 Pthreads
implementation contributed by John E. Bossom <jebossom@cognos.com>.
Many others have contributed important new code and bug fixes.

See the 'CONTRIBUTORS' file for the list of contributors.

----
Ross Johnson
<rpj@ise.canberra.edu.au>