[patch] QtGui specific patch to handle situations where SHM is not supported.

qtgui-5.9.3-fix_shm_not_supported.patch (text/plain), 1.84 KB, created by Sven Eden on 2018-02-23 09:38:05 UTC

--- a/src/plugins/platforms/xcb/qxcbbackingstore.cpp	2018-01-26 08:34:43.771873100 +0100
+++ b7src/plugins/platforms/xcb/qxcbbackingstore.cpp	2018-01-26 08:40:26.192328800 +0100
@@ -84,6 +84,7 @@
 
 private:
     void destroy();
+    static bool isShmSupported();
 
     void ensureGC(xcb_drawable_t dst);
     void flushPixmap(const QRegion &region);
@@ -143,6 +144,44 @@
     QImage *m_image;
 };
 
+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_graphics_buffer(Q_NULLPTR)
@@ -167,7 +206,9 @@
     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: %s) for size %d (%dx%d)",
                  errno, strerror(errno), segmentSize, size.width(), size.height());