Re: Cannot run Qt5 applications.
On Mar 3 14:48, Jon TURNEY wrote: On 03/03/2015 09:04, Corinna Vinschen wrote: Or you just add signal(SIGSYS, SIG_IGN) prior to calling shmget. SIGSYS is raised when calling a system call which isn't available. That's perfectly valid. This is true. I guess it's not how Linux behaves, though, so I think changing it ought to be considered to minimize porting effort. Done. HTH, Corinna -- Corinna Vinschen Please, send mails regarding Cygwin to Cygwin Maintainer cygwin AT cygwin DOT com Red Hat pgpAsbfOyZl3B.pgp Description: PGP signature
Re: Cannot run Qt5 applications.
On Mar 2 17:34, Yaakov Selkowitz wrote: On Fri, 2015-02-13 at 18:32 +, Jon TURNEY wrote: On 05/02/2015 01:40, Jon TURNEY wrote: On 04/02/2015 23:20, David Stacey wrote: I'm having difficulty running any Qt5 application. These are the commands I'm issuing: [snip] and I see the clock, so X is up and running. Then: [snip] Possibly you need to install and start cygserver (See [1]) If so, this is because Qt5 is assuming shared memory is available, which could possibly be handled in a better way... This looks like a portability problem in Qt5, where it only handles shmget() failing with a return value of -1, not with SIGSYS, to fallback to using an image in unshared memory. Patch attached. Or is it a problem with our shmget()? http://pubs.opengroup.org/onlinepubs/9699919799/functions/shmget.html http://man7.org/linux/man-pages/man2/shmget.2.html Perhaps we should be just returning -1 with an errno (ENOSYS?) instead of raise(SIGSYS)? Or you just add signal(SIGSYS, SIG_IGN) prior to calling shmget. SIGSYS is raised when calling a system call which isn't available. That's perfectly valid. Of course, it would be nice if Qt5 used POSIX shared memory objects iunstead, but that's asked too much, probably. Corinna -- Corinna Vinschen Please, send mails regarding Cygwin to Cygwin Maintainer cygwin AT cygwin DOT com Red Hat pgplD_qeT8_Zi.pgp Description: PGP signature
Re: Cannot run Qt5 applications.
On 03/03/2015 09:04, Corinna Vinschen wrote: On Mar 2 17:34, Yaakov Selkowitz wrote: On Fri, 2015-02-13 at 18:32 +, Jon TURNEY wrote: On 05/02/2015 01:40, Jon TURNEY wrote: On 04/02/2015 23:20, David Stacey wrote: I'm having difficulty running any Qt5 application. These are the commands I'm issuing: [snip] and I see the clock, so X is up and running. Then: [snip] Possibly you need to install and start cygserver (See [1]) If so, this is because Qt5 is assuming shared memory is available, which could possibly be handled in a better way... This looks like a portability problem in Qt5, where it only handles shmget() failing with a return value of -1, not with SIGSYS, to fallback to using an image in unshared memory. Patch attached. Or is it a problem with our shmget()? http://pubs.opengroup.org/onlinepubs/9699919799/functions/shmget.html http://man7.org/linux/man-pages/man2/shmget.2.html Perhaps we should be just returning -1 with an errno (ENOSYS?) instead of raise(SIGSYS)? I think it was a BSD-ism to raise SIGSYS if shared memory is not available due to policy. Historically, there must have been some OS which did this, because there is code to detect this situation in the X server [1] [1] http://cgit.freedesktop.org/xorg/xserver/tree/Xext/shm.c#n167 Looking at [2],[3] it seems perhaps this was added in Cygwin because some FreeBSD test code was used? [2] https://cygwin.com/ml/cygwin-cvs/2003-q4/msg00130.html [3] https://cygwin.com/ml/cygwin-cvs/2003-q4/msg00128.html I'd kind of assumed that modern BSDs behave in the same way, but that doesn't actually seem likely. I have absolutely no problem with changing this to return ENOSPC (there is a limit of 0 SHM identifiers, and we have reached it), or whatever is appropriate in this state. Or you just add signal(SIGSYS, SIG_IGN) prior to calling shmget. SIGSYS is raised when calling a system call which isn't available. That's perfectly valid. This is true. I guess it's not how Linux behaves, though, so I think changing it ought to be considered to minimize porting effort. I'll also note that checking once at startup, as the X server does, is not enough. If the cygserver is stopped, it will die with an unexpected SIGSYS when a client tried to use shared memory. Of course, it would be nice if Qt5 used POSIX shared memory objects instead, but that's asked too much, probably. Unfortunately, it has to use whatever the X server's MIT-SHM extension uses... -- Jon TURNEY Volunteer Cygwin/X X Server maintainer -- Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple Problem reports: http://cygwin.com/problems.html Documentation: http://x.cygwin.com/docs/ FAQ: http://x.cygwin.com/docs/faq/
Re: Cannot run Qt5 applications.
On Fri, 2015-02-13 at 18:32 +, Jon TURNEY wrote: On 05/02/2015 01:40, Jon TURNEY wrote: On 04/02/2015 23:20, David Stacey wrote: I'm having difficulty running any Qt5 application. These are the commands I'm issuing: [snip] and I see the clock, so X is up and running. Then: [snip] Possibly you need to install and start cygserver (See [1]) If so, this is because Qt5 is assuming shared memory is available, which could possibly be handled in a better way... This looks like a portability problem in Qt5, where it only handles shmget() failing with a return value of -1, not with SIGSYS, to fallback to using an image in unshared memory. Patch attached. Or is it a problem with our shmget()? http://pubs.opengroup.org/onlinepubs/9699919799/functions/shmget.html http://man7.org/linux/man-pages/man2/shmget.2.html Perhaps we should be just returning -1 with an errno (ENOSYS?) instead of raise(SIGSYS)? -- Yaakov -- Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple Problem reports: http://cygwin.com/problems.html Documentation: http://x.cygwin.com/docs/ FAQ: http://x.cygwin.com/docs/faq/
Re: Cannot run Qt5 applications.
On 05/02/2015 01:40, Jon TURNEY wrote:
On 04/02/2015 23:20, David Stacey wrote:
I'm having difficulty running any Qt5 application. These are the
commands I'm issuing:
XWin -multiwindow
export DISPLAY=:0.0
xclock
and I see the clock, so X is up and running. Then:
/usr/lib/qt5/examples/gui/analogclock/analogclock
QXcbConnection: XCB error: 145 (Unknown), sequence: 162, resource
id: 0, major c
ode: 140 (Unknown), minor code: 20
Bad system call (core dumped)
Possibly you need to install and start cygserver (See [1])
If so, this is because Qt5 is assuming shared memory is available, which
could possibly be handled in a better way...
[1] http://x.cygwin.com/docs/ug/using-shared-memory.html
Yaakov,
This looks like a portability problem in Qt5, where it only handles
shmget() failing with a return value of -1, not with SIGSYS, to fallback
to using an image in unshared memory.
Patch attached.
--
Jon TURNEY
Volunteer Cygwin/X X Server maintainer
---
origsrc/qtbase-opensource-src-5.3.2/src/plugins/platforms/xcb/qxcbbackingstore.cpp
2014-09-11 11:48:06.0 +0100
+++
src/qtbase-opensource-src-5.3.2/src/plugins/platforms/xcb/qxcbbackingstore.cpp
2015-02-13 17:30:11.410525500 +
@@ -75,6 +75,7 @@ public:
private:
void destroy();
+static bool isShmSupported();
xcb_shm_segment_info_t m_shm_info;
@@ -88,6 +89,44 @@ private:
QRegion m_dirty;
};
+static bool shmNotSupported = false;
+
+static void
+SigSysHandler(int signo)
+{
+shmNotSupported = true;
+}
+
+bool
+QXcbShmImage::isShmSupported()
+{
+static bool checked = false;
+if (!checked)
+ {
+void (*oldHandler)(int);
+int shmid = -1;
+
+/* If no SHM support in the kernel, the bad syscall will generate
SIGSYS */
+oldHandler = signal(SIGSYS, SigSysHandler);
+
+shmNotSupported = false;
+shmid = shmget(IPC_PRIVATE, 4096, IPC_CREAT);
+if (shmid != -1)
+ {
+/* Successful allocation - clean up */
+shmctl(shmid, IPC_RMID, NULL);
+ }
+else
+ {
+/* Allocation failed */
+shmNotSupported = true;
+ }
+signal(SIGSYS, oldHandler);
+checked = true;
+ }
+return (!shmNotSupported);
+}
+
QXcbShmImage::QXcbShmImage(QXcbScreen *screen, const QSize size, uint depth,
QImage::Format format)
: QXcbObject(screen-connection())
, m_gc(0)
@@ -116,7 +155,9 @@ QXcbShmImage::QXcbShmImage(QXcbScreen *s
if (!segmentSize)
return;
-int id = shmget(IPC_PRIVATE, segmentSize, IPC_CREAT | 0600);
+int id = -1;
+if (isShmSupported())
+ id = shmget(IPC_PRIVATE, segmentSize, IPC_CREAT | 0600);
if (id == -1)
qWarning(QXcbShmImage: shmget() failed (%d) for size %d (%dx%d),
errno, segmentSize, size.width(), size.height());
@@ -130,7 +171,7 @@ QXcbShmImage::QXcbShmImage(QXcbScreen *s
xcb_generic_error_t *error = NULL;
if (shm_present)
error = xcb_request_check(xcb_connection(),
xcb_shm_attach_checked(xcb_connection(), m_shm_info.shmseg, m_shm_info.shmid,
false));
-if (!shm_present || error) {
+if (!shm_present || error || (id == -1)) {
free(error);
shmdt(m_shm_info.shmaddr);
--
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Re: Cannot run Qt5 applications.
On 05/02/15 01:40, Jon TURNEY wrote: On 04/02/2015 23:20, David Stacey wrote: I'm having difficulty running any Qt5 application. These are the commands I'm issuing: XWin -multiwindow export DISPLAY=:0.0 xclock and I see the clock, so X is up and running. Then: /usr/lib/qt5/examples/gui/analogclock/analogclock QXcbConnection: XCB error: 145 (Unknown), sequence: 162, resource id: 0, major c ode: 140 (Unknown), minor code: 20 Bad system call (core dumped) Possibly you need to install and start cygserver (See [1]) If so, this is because Qt5 is assuming shared memory is available, which could possibly be handled in a better way... Yes, that did the trick - thank you. I would never have figured that our from the error message! Dave. -- Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple Problem reports: http://cygwin.com/problems.html Documentation: http://x.cygwin.com/docs/ FAQ: http://x.cygwin.com/docs/faq/
Re: Cannot run Qt5 applications.
On 04/02/2015 23:20, David Stacey wrote: I'm having difficulty running any Qt5 application. These are the commands I'm issuing: XWin -multiwindow export DISPLAY=:0.0 xclock and I see the clock, so X is up and running. Then: /usr/lib/qt5/examples/gui/analogclock/analogclock QXcbConnection: XCB error: 145 (Unknown), sequence: 162, resource id: 0, major c ode: 140 (Unknown), minor code: 20 Bad system call (core dumped) Possibly you need to install and start cygserver (See [1]) If so, this is because Qt5 is assuming shared memory is available, which could possibly be handled in a better way... [1] http://x.cygwin.com/docs/ug/using-shared-memory.html -- Jon TURNEY Volunteer Cygwin/X X Server maintainer -- Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple Problem reports: http://cygwin.com/problems.html Documentation: http://x.cygwin.com/docs/ FAQ: http://x.cygwin.com/docs/faq/
