mirror of https://github.com/PCSX2/pcsx2.git
404 lines
15 KiB
Plaintext
404 lines
15 KiB
Plaintext
=========================================
|
|
PTHREADS-WIN32 Frequently Asked Questions
|
|
=========================================
|
|
|
|
INDEX
|
|
-----
|
|
|
|
Q 1 What is it?
|
|
|
|
Q 2 Which of the several dll versions do I use?
|
|
or,
|
|
What are all these pthread*.dll and pthread*.lib files?
|
|
|
|
Q 3 What is the library naming convention?
|
|
|
|
Q 4 Cleanup code default style or: it used to work when I built
|
|
the library myself, but now it doesn't - why?
|
|
|
|
Q 5 Why is the default library version now less exception-friendly?
|
|
|
|
Q 6 Should I use Cygwin or Mingw32 as a development environment?
|
|
|
|
Q 7 Now that pthreads-win32 builds under Mingw32, why do I get
|
|
memory access violations (segfaults)?
|
|
|
|
Q 8 How do I use pthread.dll for Win32 (Visual C++ 5.0)
|
|
|
|
Q 9 Cancelation doesn't work for me, why?
|
|
|
|
Q 10 How do I generate pthreadGCE.dll and libpthreadw32.a for use
|
|
with Mingw32?
|
|
|
|
=============================================================================
|
|
|
|
Q 1 What is it?
|
|
---
|
|
|
|
Pthreads-win32 is an Open Source Software 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. The library also supports
|
|
some of the functionality of the Open Group's Single Unix
|
|
specification, version 2, namely mutex types.
|
|
|
|
See the file "ANNOUNCE" for more information including standards
|
|
conformance details and list of supported routines.
|
|
|
|
|
|
------------------------------------------------------------------------------
|
|
|
|
Q 2 Which of the several dll versions do I use?
|
|
--- or,
|
|
What are all these pthread*.dll and pthread*.lib files?
|
|
|
|
Simply, you only use one of them, but you need to choose carefully.
|
|
|
|
The most important choice you need to make is whether to use a
|
|
version that uses exceptions internally, or not (there are versions
|
|
of the library that use exceptions as part of the thread
|
|
cancelation and cleanup implementation, and one that uses
|
|
setjmp/longjmp instead).
|
|
|
|
There is some contension amongst POSIX threads experts as
|
|
to how POSIX threads cancelation and exit should work
|
|
with languages that include exceptions and handlers, e.g.
|
|
C++ and even C (Microsoft's Structured Exceptions).
|
|
|
|
The issue is: should cancelation of a thread in, say,
|
|
a C++ application cause object destructors and C++ exception
|
|
handlers to be invoked as the stack unwinds during thread
|
|
exit, or not?
|
|
|
|
There seems to be more opinion in favour of using the
|
|
standard C version of the library (no EH) with C++ applications
|
|
since this appears to be the assumption commercial pthreads
|
|
implementations make. Therefore, if you use an EH version
|
|
of pthreads-win32 then you may be under the illusion that
|
|
your application will be portable, when in fact it is likely to
|
|
behave very differently linked with other pthreads libraries.
|
|
|
|
Now you may be asking: why have you kept the EH versions of
|
|
the library?
|
|
|
|
There are a couple of reasons:
|
|
- there is division amongst the experts and so the code may
|
|
be needed in the future. (Yes, it's in the repository and we
|
|
can get it out anytime in the future, but ...)
|
|
- pthreads-win32 is one of the few implementations, and possibly
|
|
the only freely available one, that has EH versions. It may be
|
|
useful to people who want to play with or study application
|
|
behaviour under these conditions.
|
|
|
|
|
|
------------------------------------------------------------------------------
|
|
|
|
Q 3 What is the library naming convention?
|
|
---
|
|
|
|
Because the library is being built using various exception
|
|
handling schemes and compilers - and because the library
|
|
may not work reliably if these are mixed in an application,
|
|
each different version of the library has it's own name.
|
|
|
|
Note 1: the incompatibility is really between EH implementations
|
|
of the different compilers. It should be possible to use the
|
|
standard C version from either compiler with C++ applications
|
|
built with a different compiler. If you use an EH version of
|
|
the library, then you must use the same compiler for the
|
|
application. This is another complication and dependency that
|
|
can be avoided by using only the standard C library version.
|
|
|
|
Note 2: if you use a standard C pthread*.dll with a C++
|
|
application, then any functions that you define that are
|
|
intended to be called via pthread_cleanup_push() must be
|
|
__cdecl.
|
|
|
|
Note 3: the intention is to also name either the VC or GC
|
|
version (it should be arbitrary) as pthread.dll, including
|
|
pthread.lib and libpthread.a as appropriate.
|
|
|
|
In general:
|
|
pthread[VG]{SE,CE,C}.dll
|
|
pthread[VG]{SE,CE,C}.lib
|
|
|
|
where:
|
|
[VG] indicates the compiler
|
|
V - MS VC
|
|
G - GNU C
|
|
|
|
{SE,CE,C} indicates the exception handling scheme
|
|
SE - Structured EH
|
|
CE - C++ EH
|
|
C - no exceptions - uses setjmp/longjmp
|
|
|
|
For example:
|
|
pthreadVSE.dll (MSVC/SEH)
|
|
pthreadGCE.dll (GNUC/C++ EH)
|
|
pthreadGC.dll (GNUC/not dependent on exceptions)
|
|
|
|
The GNU library archive file names have changed to:
|
|
|
|
libpthreadGCE.a
|
|
libpthreadGC.a
|
|
|
|
|
|
------------------------------------------------------------------------------
|
|
|
|
Q 4 Cleanup code default style or: it used to work when I built
|
|
--- the library myself, but now it doesn't - why?
|
|
|
|
Up to and including snapshot 2001-07-12, if not defined, the cleanup
|
|
style was determined automatically from the compiler used, 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().
|
|
|
|
After snapshot 2001-07-12, unless your 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/all
|
|
commercial Unix POSIX threads implementations.
|
|
|
|
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
|
|
|
|
THE POINT OF ALL THIS IS: if you have not been defining one of these
|
|
explicitly, then the defaults have been set according to the compiler
|
|
and language you are using, as described at the top of this
|
|
section.
|
|
|
|
THIS NOW CHANGES, as has been explained above. For example:
|
|
|
|
If you were building your application with MSVC++ i.e. using C++
|
|
exceptions (rather than SEH) and not explicitly defining one of
|
|
__CLEANUP_*, then __CLEANUP_C++ was 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
|
|
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, nor when 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 local
|
|
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.
|
|
|
|
|
|
------------------------------------------------------------------------------
|
|
|
|
Q 5 Why is the default library version now less exception-friendly?
|
|
---
|
|
|
|
Because most commercial Unix POSIX threads implementations don't allow you to
|
|
choose to have stack unwinding. (Compaq's TRU64 Unix is possibly an exception.)
|
|
|
|
Therefore, providing it in pthread-win32 as a default could be dangerous
|
|
and non-portable. We still provide the choice but you must now consciously
|
|
make it.
|
|
|
|
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.)
|
|
- 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.
|
|
|
|
|
|
------------------------------------------------------------------------------
|
|
|
|
Q 6 Should I use Cygwin or Mingw32 as a development environment?
|
|
---
|
|
|
|
Important: see Q7 also.
|
|
|
|
Use Mingw32 with the MSVCRT library to build applications that use
|
|
the pthreads DLL.
|
|
|
|
Cygwin's own internal support for POSIX threads is growing.
|
|
Consult that project's documentation for more information.
|
|
|
|
------------------------------------------------------------------------------
|
|
|
|
Q 7 Now that pthreads-win32 builds under Mingw32, why do I get
|
|
--- memory access violations (segfaults)?
|
|
|
|
The latest Mingw32 package has thread-safe exception handling (see Q10).
|
|
Also, see Q6 above.
|
|
|
|
------------------------------------------------------------------------------
|
|
|
|
Q 8 How do I use pthread.dll for Win32 (Visual C++ 5.0)
|
|
---
|
|
|
|
>
|
|
> I'm a "rookie" when it comes to your pthread implementation. I'm currently
|
|
> desperately trying to install the prebuilt .dll file into my MSVC compiler.
|
|
> Could you please provide me with explicit instructions on how to do this (or
|
|
> direct me to a resource(s) where I can acquire such information)?
|
|
>
|
|
> Thank you,
|
|
>
|
|
|
|
You should have a .dll, .lib, .def, and three .h files. It is recommended
|
|
that you use pthreadVC.dll, rather than pthreadVCE.dll or pthreadVSE.dll
|
|
(see Q2 above).
|
|
|
|
The .dll can go in any directory listed in your PATH environment
|
|
variable, so putting it into C:\WINDOWS should work.
|
|
|
|
The .lib file can go in any directory listed in your LIB environment
|
|
variable.
|
|
|
|
The .h files can go in any directory listed in your INCLUDE
|
|
environment variable.
|
|
|
|
Or you might prefer to put the .lib and .h files into a new directory
|
|
and add its path to LIB and INCLUDE. You can probably do this easiest
|
|
by editing the file:-
|
|
|
|
C:\Program Files\DevStudio\vc\bin\vcvars32.bat
|
|
|
|
The .def file isn't used by anything in the pre-compiled version but
|
|
is included for information.
|
|
|
|
Cheers.
|
|
Ross
|
|
|
|
------------------------------------------------------------------------------
|
|
|
|
Q 9 Cancelation doesn't work for me, why?
|
|
---
|
|
|
|
> I'm investigating a problem regarding thread cancelation. The thread I want
|
|
> to cancel has PTHREAD_CANCEL_ASYNCHRONOUS, however, this piece of code
|
|
> blocks on the join():
|
|
>
|
|
> if ((retv = Pthread_cancel( recvThread )) == 0)
|
|
> {
|
|
> retv = Pthread_join( recvThread, 0 );
|
|
> }
|
|
>
|
|
> Pthread_* are just macro's; they call pthread_*.
|
|
>
|
|
> The thread recvThread seems to block on a select() call. It doesn't get
|
|
> cancelled.
|
|
>
|
|
> Two questions:
|
|
>
|
|
> 1) is this normal behaviour?
|
|
>
|
|
> 2) if not, how does the cancel mechanism work? I'm not very familliar to
|
|
> win32 programming, so I don't really understand how the *Event() family of
|
|
> calls work.
|
|
|
|
The answer to your first question is, normal POSIX behaviour would
|
|
be to asynchronously cancel the thread. However, even that doesn't
|
|
guarantee cancelation as the standard only says it should be
|
|
cancelled as soon as possible.
|
|
|
|
Snapshot 99-11-02 or earlier only partially supports asynchronous cancellation.
|
|
Snapshots since then simulate async cancelation by poking the address of
|
|
a cancelation routine into the PC of the threads context. This requires
|
|
the thread to be resumed in some way for the cancelation to actually
|
|
proceed. This is not true async cancelation, but it is as close as we've
|
|
been able to get to it.
|
|
|
|
If the thread you're trying to cancel is blocked (for instance, it could be
|
|
waiting for data from the network), it will only get cancelled when it unblocks
|
|
(when the data arrives). For true pre-emptive cancelation in these cases,
|
|
pthreads-win32 from snapshot 2004-05-16 can automatically recognise and use the
|
|
QueueUserAPCEx package by Panagiotis E. Hadjidoukas. This package is available
|
|
from the pthreads-win32 ftp site and is included in the pthreads-win32
|
|
self-unpacking zip from 2004-05-16 onwards.
|
|
|
|
Using deferred cancelation would normally be the way to go, however,
|
|
even though the POSIX threads standard lists a number of C library
|
|
functions that are defined as deferred cancelation points, there is
|
|
no hookup between those which are provided by Windows and the
|
|
pthreads-win32 library.
|
|
|
|
Incidently, it's worth noting for code portability that the older POSIX
|
|
threads standards cancelation point lists didn't include "select" because
|
|
(as I read in Butenhof) it wasn't part of POSIX. However, it does appear in
|
|
the SUSV3.
|
|
|
|
Effectively, the only mandatory cancelation points that pthreads-win32
|
|
recognises are those the library implements itself, ie.
|
|
|
|
pthread_testcancel
|
|
pthread_cond_wait
|
|
pthread_cond_timedwait
|
|
pthread_join
|
|
sem_wait
|
|
sem_timedwait
|
|
pthread_delay_np
|
|
|
|
The following routines from the non-mandatory list in SUSV3 are
|
|
cancelation points in pthreads-win32:
|
|
|
|
pthread_rwlock_wrlock
|
|
pthread_rwlock_timedwrlock
|
|
|
|
The following routines from the non-mandatory list in SUSV3 are not
|
|
cancelation points in pthreads-win32:
|
|
|
|
pthread_rwlock_rdlock
|
|
pthread_rwlock_timedrdlock
|
|
|
|
Pthreads-win32 also provides two functions that allow you to create
|
|
cancelation points within your application, but only for cases where
|
|
a thread is going to block on a Win32 handle. These are:
|
|
|
|
pthreadCancelableWait(HANDLE waitHandle) /* Infinite wait */
|
|
|
|
pthreadCancelableTimedWait(HANDLE waitHandle, DWORD timeout)
|
|
|
|
------------------------------------------------------------------------------
|
|
|
|
|
|
Q 10 How do I create thread-safe applications using
|
|
---- pthreadGCE.dll, libpthreadw32.a and Mingw32?
|
|
|
|
This should not be a problem with recent versions of MinGW32.
|
|
|
|
For early versions, see Thomas Pfaff's email at:
|
|
http://sources.redhat.com/ml/pthreads-win32/2002/msg00000.html
|
|
------------------------------------------------------------------------------
|
|
|