of atomic implementatition, making it possible to force the use of Mutex for OpenThreads::Atomic,
and as a consequence for use of Mutex for Referenced::ref/unref() counting.
"
and a later post the same osg-submissions thread:
"it's been a while since I have made the changes but I think it was due to problems with static builds of OpenThreads on windows. I was using
OpenThreads in a communication/synchronisation library (without
OpenSceneGraph). It seems I forgot to post a small change in the CMakeLists file of OpenThreads. If a user turns DYNAMIC_OPENTHREADS to OFF (static build) OT_LIBRARY_STATIC will be defined in the Config.
Without these changes a windows user will always end up with a "__declspec(dllexport)" or "__declspec(dllimport)" which is a problem for static builds."
And another post from Blasius on this topic:
"I tested with VS2005 and VS2008. For 32 bit everything works as expected. For x64 and VS2008 I could successfully do the cmake-configure and then the compilation but I had occasional crashes of cmTryCompileExec.exe (during the cmake-configure phase) which seems to be a cmake bug. With VS2005 and 64bit cmake does not set _OPENTHREADS_ATOMIC_USE_WIN32_INTERLOCKED although the interlocked functionality should be there. If I place the source snippet from the CHECK_CXX_SOURCE_RUNS macro to a separate sourcefile I can compile and run the resulting executable successfully. Forcing OPENTHREADS_ATOMIC_USE_WIN32_INTERLOCKED (on VS2005/x64) reveals a bug in "intrin.h" which seems to be fixed in VS2008 but not in VS2005.
In case anyone is interested the lines:
__MACHINEI(unsigned char _interlockedbittestandset(long *a, long b))
__MACHINEI(unsigned char _interlockedbittestandreset(long *a, long b))
__MACHINEX64(unsigned char _interlockedbittestandset64(__int64 *a, __int64 b))
__MACHINEX64(unsigned char _interlockedbittestandreset64(__int64 *a, __int64 b))
should be changed to:
__MACHINEI(unsigned char _interlockedbittestandset(long volatile *a, long b))
__MACHINEI(unsigned char _interlockedbittestandreset(long volatile *a, long b))
__MACHINEX64(unsigned char _interlockedbittestandset64(__int64 volatile *a, __int64 b))
__MACHINEX64(unsigned char _interlockedbittestandreset64(__int64 volatile *a, __int64 b))
The worst thing that can happen is that interlocked funtionality is not detected during cmake-configure and the mutex fallback is used.
Which reminds me another small glitch in the Atomic header so I attached a corrected version.
Why is the OT_LIBRARY_STATIC added to the config file? It is not needed anywhere.
OT_LIBRARY_STATIC is needed if you are doing static-builds on Windows. See my previous post on that.
"
MemoryBarrier() is used in the implementation, so it should be checked.
This in effect disables the faster atomic ops on msvc 7.1 and older, even if
only the MemoryBarrier() call is missing. But it ensures for the fist cut
that it will build everywhere. If somebody cares for msvc 7.1 enough and has
one for testing installed, he might provide the apropriate defines to guard
that MemoryBarrier() call.
I tested that msvc8 32/64bit still passes the configure tests and compiles.
"
implementation of the atomic increment and decrement into a implementation
file.
This way inlining and compiler optimization can no longer happen for these
implementations, but it fixes compilation on win32 msvc targets. I expect
that this is still faster than with with mutexes.
Also the i386 gcc target gets atomic operations with this patch. By using an
implementation file we can guarantee that we have the right compiler flags
available."
atomic related compile failures with msvs2005. Attached changes to make win32
really use the atomic stuff. There are pointer typecast problems and some
historic alignment restrictions that I just took from a previous similar
implementation of mine without looking deep enough. "
