From d4efd5ab810e92202efe672be29136324dd2a3f9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?D=C4=81vis=20Mos=C4=81ns?= <davispuh@gmail.com>
Date: Mon, 28 Dec 2015 05:43:18 +0200
Subject: [PATCH] Check for NULL from glGetString

glGetString can return NULL pointer in case of error
so check for it before using.

Change-Id: Ia07424c8f2b3ce6dce675514900a509e3ef3b739
---
 src/particles/qquickimageparticle.cpp              |  6 ++++--
 src/quick/scenegraph/qsgcontext.cpp                | 22 ++++++++++++++++------
 .../qsgdefaultdistancefieldglyphcache.cpp          |  8 +++++---
 src/quick/scenegraph/util/qsgatlastexture.cpp      |  4 ++--
 4 files changed, 27 insertions(+), 13 deletions(-)

diff --git a/src/particles/qquickimageparticle.cpp b/src/particles/qquickimageparticle.cpp
index d78a350..b54861e 100644
--- a/src/particles/qquickimageparticle.cpp
+++ b/src/particles/qquickimageparticle.cpp
@@ -1276,14 +1276,16 @@ void QQuickImageParticle::finishBuildParticleNodes(QSGNode** node)
     // OS X 10.8.3 introduced a bug in the AMD drivers, for at least the 2011 macbook pros,
     // causing point sprites who read gl_PointCoord in the frag shader to come out as
     // green-red blobs.
-    if (perfLevel < Deformable && strstr((char *) glGetString(GL_VENDOR), "ATI")) {
+    const char *vendor = (const char *) glGetString(GL_VENDOR);
+    if (perfLevel < Deformable && vendor && strstr(vendor, "ATI")) {
         perfLevel = Deformable;
     }
 #endif
 
 #ifdef Q_OS_LINUX
     // Nouveau drivers can potentially freeze a machine entirely when taking the point-sprite path.
-    if (perfLevel < Deformable && strstr((const char *) glGetString(GL_VENDOR), "nouveau"))
+    const char *vendor = (const char *) glGetString(GL_VENDOR);
+    if (perfLevel < Deformable && vendor && strstr(vendor, "nouveau"))
         perfLevel = Deformable;
 #endif
 
diff --git a/src/quick/scenegraph/qsgcontext.cpp b/src/quick/scenegraph/qsgcontext.cpp
index dd6977e..43d549f 100644
--- a/src/quick/scenegraph/qsgcontext.cpp
+++ b/src/quick/scenegraph/qsgcontext.cpp
@@ -624,14 +624,24 @@ void QSGRenderContext::initialize(QOpenGLContext *context)
     m_sg->renderContextInitialized(this);
 
 #ifdef Q_OS_LINUX
+    while (funcs->glGetError() != GL_NO_ERROR);
+
     const char *vendor = (const char *) funcs->glGetString(GL_VENDOR);
-    if (strstr(vendor, "nouveau"))
-        m_brokenIBOs = true;
     const char *renderer = (const char *) funcs->glGetString(GL_RENDERER);
-    if (strstr(renderer, "llvmpipe"))
-        m_serializedRender = true;
-    if (strstr(vendor, "Hisilicon Technologies") && strstr(renderer, "Immersion.16"))
-        m_brokenIBOs = true;
+
+    if (vendor && renderer) {
+        if (strstr(vendor, "nouveau"))
+            m_brokenIBOs = true;
+        if (strstr(renderer, "llvmpipe"))
+            m_serializedRender = true;
+        if (strstr(vendor, "Hisilicon Technologies") && strstr(renderer, "Immersion.16"))
+            m_brokenIBOs = true;
+    } else {
+        GLenum err;
+        while ((err = funcs->glGetError()) != GL_NO_ERROR) {
+            qWarning("QSGRenderContext::initialize: GL error %x from glGetString", err);
+        }
+    }
 #endif
 
     emit initialized();
diff --git a/src/quick/scenegraph/qsgdefaultdistancefieldglyphcache.cpp b/src/quick/scenegraph/qsgdefaultdistancefieldglyphcache.cpp
index dcc485c..43e234b 100644
--- a/src/quick/scenegraph/qsgdefaultdistancefieldglyphcache.cpp
+++ b/src/quick/scenegraph/qsgdefaultdistancefieldglyphcache.cpp
@@ -488,9 +488,11 @@ bool QSGDefaultDistanceFieldGlyphCache::useTextureUploadWorkaround() const
     static bool set = false;
     static bool useWorkaround = false;
     if (!set) {
-        useWorkaround = qstrcmp(reinterpret_cast<const char*>(m_funcs->glGetString(GL_RENDERER)),
-                                "Mali-400 MP") == 0;
-        set = true;
+        const char *renderer = reinterpret_cast<const char*>(m_funcs->glGetString(GL_RENDERER));
+        if (renderer) {
+            useWorkaround = qstrcmp(renderer, "Mali-400 MP") == 0;
+            set = true;
+        }
     }
     return useWorkaround;
 }
-- 
1.9.3