QCoreApplication::applicationFilePath(): Fix array bounds violation of argv.

Check for argc > 0 before accessing argv[0].

tst_qapplication constructs QApplication(0, 0) and has been
observed to crash sporadically. Fix valgrind error:

=9845== Conditional jump or move depends on uninitialised value(s)
==9845==    at 0x4C2F1BC: strcmp (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==9845==    by 0x5DEEFB3: qstrcmp(char const*, char const*) (qbytearray.cpp:262)
==9845==    by 0x6011EAA: QCoreApplication::applicationFilePath() (qcoreapplication.cpp:2058)
==9845==    by 0x6011D0B: QCoreApplication::applicationDirPath() (qcoreapplication.cpp:2029)
==9845==    by 0x5DD285D: QLibraryInfoPrivate::findConfiguration() (qlibraryinfo.cpp:184)
==9845==    by 0x5DD32AF: QLibraryInfo::platformPluginArguments(QString const&) (qlibraryinfo.cpp:596)
==9845==    by 0x5746A95: init_platform(QString const&, QString const&, QString const&, int&, char**) (qguiapplication.cpp:1017)
==9845==    by 0x5747C91: QGuiApplicationPrivate::createPlatformIntegration() (qguiapplication.cpp:1177)
==9845==    by 0x5747DDE: QGuiApplicationPrivate::createEventDispatcher() (qguiapplication.cpp:1194)
==9845==    by 0x4FAF81D: QApplicationPrivate::createEventDispatcher() (qapplication.cpp:196)
==9845==    by 0x600F568: QCoreApplication::init() (qcoreapplication.cpp:768)
==9845==    by 0x600F2C4: QCoreApplication::QCoreApplication(QCoreApplicationPrivate&) (qcoreapplication.cpp:689)
==9845==    by 0x574594C: QGuiApplication::QGuiApplication(QGuiApplicationPrivate&) (qguiapplication.cpp:570)
==9845==    by 0x4FB008A: QApplication::QApplication(int&, char**, int) (qapplication.cpp:569)
==9845==    by 0x41148A: tst_QApplication::lastWindowClosed() (tst_qapplication.cpp:561)

Change-Id: I2fb324ab63617f14f5f43835154aae339bfa9520
Reviewed-by: Simon Hausmann <simon.hausmann@theqtcompany.com>

1 files changed, 7 insertions, 5 deletions

diff --git a/src/corelib/kernel/qcoreapplication.cpp b/src/corelib/kernel/qcoreapplication.cpp
index b6f839d554..34dad73c80 100644
--- a/src/corelib/kernel/qcoreapplication.cpp
+++ b/src/corelib/kernel/qcoreapplication.cpp
@@ -2054,11 +2054,13 @@ QString QCoreApplication::applicationFilePath()
 
     QCoreApplicationPrivate *d = self->d_func();
 
-    static char *procName = d->argv[0];
-    if (qstrcmp(procName, d->argv[0]) != 0) {
-        // clear the cache if the procname changes, so we reprocess it.
-        QCoreApplicationPrivate::clearApplicationFilePath();
-        procName = d->argv[0];
+    if (d->argc) {
+        static const char *procName = d->argv[0];
+        if (qstrcmp(procName, d->argv[0]) != 0) {
+            // clear the cache if the procname changes, so we reprocess it.
+            QCoreApplicationPrivate::clearApplicationFilePath();
+            procName = d->argv[0];
+        }
     }
 
     if (QCoreApplicationPrivate::cachedApplicationFilePath)