Don't assume QCoreApplication::applicationName() will never change

Tests will typically create multiple QCoreApplications, some of them
with different argv[0] than others, so we can't use a static variable
to keep the cached application name.

Change-Id: Icd97527730558944473a71373326b4a82f1b7cf7
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/kernel/qcoreapplication.cpp

@@ -146,15 +146,17 @@ QString QCoreApplicationPrivate::macMenuBarName()
 #endif
 QString QCoreApplicationPrivate::appName() const
 {
-    static QString applName;
+    if (applicationName.isNull()) {
 #ifdef Q_OS_MAC
-    applName = macMenuBarName();
+        applicationName = macMenuBarName();
 #endif
-    if (applName.isEmpty() && argv[0]) {
-        char *p = strrchr(argv[0], '/');
-        applName = QString::fromLocal8Bit(p ? p + 1 : argv[0]);
+        if (applicationName.isEmpty() && argv[0]) {
+            char *p = strrchr(argv[0], '/');
+            applicationName = QString::fromLocal8Bit(p ? p + 1 : argv[0]);
+        }
     }
-    return applName;
+
+    return applicationName;
 }
 #endif
 

src/corelib/kernel/qcoreapplication_p.h

@@ -83,6 +83,7 @@ public:
     ~QCoreApplicationPrivate();
 
     QString appName() const;
+    mutable QString applicationName;
 
 #ifdef Q_OS_MAC
     static QString macMenuBarName();