<![CDATA[Is is possible to create a semaphore accessable to both Windows and Qt applications?]]>I tried to create a named semaphore in a Windows application using following code:

m_hSemaphore = ::CreateSemaphore(NULL, 0, 100, "semaphore_test");

and in my Qt application I open a semaphore of the same name:

pSemaphore = new QSystemSemaphore(tr("semaphore_test"), 0, QSystemSemaphore::Open);

But when the semaphore is released in Windows application, in Qt application,

m_pSemaphore->acquire();

is still blocked, which means two applications are not accessing the samesemaphore.

Is there a way to make both applications access the same semaphore? The similar problem also exists in accessing shared memory in both Windows and Qt applications.

]]>https://forum.qt.io/topic/20897/is-is-possible-to-create-a-semaphore-accessable-to-both-windows-and-qt-applicationsRSS for NodeWed, 22 Jul 2026 04:33:53 GMTThu, 25 Oct 2012 16:51:53 GMT60<![CDATA[Reply to Is is possible to create a semaphore accessable to both Windows and Qt applications? on Mon, 29 Oct 2012 15:12:50 GMT]]>I see, thanks! By the way, I just noticed that QSharedMemory::setNativeKey will set the native, platform specific key for this shared memory object, that will also help in Qt code to connect to shared memory created from Windows code.

]]>https://forum.qt.io/post/155691https://forum.qt.io/post/155691Mon, 29 Oct 2012 15:12:50 GMT<![CDATA[Reply to Is is possible to create a semaphore accessable to both Windows and Qt applications? on Fri, 26 Oct 2012 22:18:48 GMT]]>I'm now at home and just check it. It does show up! But as a "section", not as a "file" ;-)

Example:
@\Sessions\1\BaseNamedObjects\qipc_sharedmemory_AAbbCFBFEEc953e91dc88f95245766d85214a816f620994f01@

]]>https://forum.qt.io/post/155531https://forum.qt.io/post/155531Fri, 26 Oct 2012 22:18:48 GMT<![CDATA[Reply to Is is possible to create a semaphore accessable to both Windows and Qt applications? on Fri, 26 Oct 2012 17:55:39 GMT]]>No, it does not show up.

]]>https://forum.qt.io/post/155521https://forum.qt.io/post/155521Fri, 26 Oct 2012 17:55:39 GMT<![CDATA[Reply to Is is possible to create a semaphore accessable to both Windows and Qt applications? on Fri, 26 Oct 2012 15:12:14 GMT]]>bq. Thank you very much for your help! Now I can make Windows application and Qt application use a same semaphore.
ProcessExplorer does not show shared memory used by a process, so making Windows application and Qt application use same shared memory is still a problem. Any ideas?

The "shared" memory is nothing but a "memory mapped file", one that is backed by the system page file rather than by a file system file. Doesn't it show up under the file handles in ProcessExplorer?

]]>https://forum.qt.io/post/155508https://forum.qt.io/post/155508Fri, 26 Oct 2012 15:12:14 GMT<![CDATA[Reply to Is is possible to create a semaphore accessable to both Windows and Qt applications? on Thu, 25 Oct 2012 18:53:01 GMT]]>AFAIK Qt will decorate the Semaphore name, when using QSystemSemaphore().

You can use a tool such as ProcessExplorer to lookup the actual (native) name of the Semaphore...

http://technet.microsoft.com/de-de/sysinternals/bb896653.aspx

!http://imageshack.us/a/img690/9056/clipboard01yi.png(Screenshot from ProcessExplorer)!

Looks like the string "qipc_systemsem_" followed by a hash of the specified string is used ;-)

]]>https://forum.qt.io/post/155428https://forum.qt.io/post/155428Thu, 25 Oct 2012 18:53:01 GMT