QStandardPaths: warn if $XDG_RUNTIME_DIR doesn't exist

If the environment variable is set, but points to a non-existing directory,
the user would get a warning about chmod failing. Better be clear and
warn about the fact that the directory itself doesn't exist.

Also warn if $XDG_RUNTIME_DIR points to a file rather than a directory.

Task-number: QTBUG-48771
Change-Id: If84e72d768528ea4b80260afbbc18709b7b738a8
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>

src/corelib/io/qstandardpaths_unix.cpp

@@ -113,21 +113,33 @@ QString QStandardPaths::writableLocation(StandardLocation type)
     {
         const uid_t myUid = geteuid();
         // http://standards.freedesktop.org/basedir-spec/latest/
+        QFileInfo fileInfo;
         QString xdgRuntimeDir = QFile::decodeName(qgetenv("XDG_RUNTIME_DIR"));
         if (xdgRuntimeDir.isEmpty()) {
             const QString userName = QFileSystemEngine::resolveUserName(myUid);
             xdgRuntimeDir = QDir::tempPath() + QLatin1String("/runtime-") + userName;
-            QDir dir(xdgRuntimeDir);
+            fileInfo.setFile(xdgRuntimeDir);
-            if (!dir.exists()) {
+            if (!fileInfo.isDir()) {
                 if (!QDir().mkdir(xdgRuntimeDir)) {
                     qWarning("QStandardPaths: error creating runtime directory %s: %s", qPrintable(xdgRuntimeDir), qPrintable(qt_error_string(errno)));
                     return QString();
                 }
             }
             qWarning("QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '%s'", qPrintable(xdgRuntimeDir));
+        } else {
+            fileInfo.setFile(xdgRuntimeDir);
+            if (!fileInfo.exists()) {
+                qWarning("QStandardPaths: XDG_RUNTIME_DIR points to non-existing path '%s', "
+                         "please create it with 0700 permissions.", qPrintable(xdgRuntimeDir));
+                return QString();
+            }
+            if (!fileInfo.isDir()) {
+                qWarning("QStandardPaths: XDG_RUNTIME_DIR points to '%s' which is not a directory",
+                         qPrintable(xdgRuntimeDir));
+                return QString();
+            }
         }
         // "The directory MUST be owned by the user"
-        QFileInfo fileInfo(xdgRuntimeDir);
         if (fileInfo.ownerId() != myUid) {
             qWarning("QStandardPaths: wrong ownership on runtime directory %s, %d instead of %d", qPrintable(xdgRuntimeDir),
                      fileInfo.ownerId(), myUid);
@@ -135,14 +147,16 @@ QString QStandardPaths::writableLocation(StandardLocation type)
         }
         // "and he MUST be the only one having read and write access to it. Its Unix access mode MUST be 0700."
         // since the current user is the owner, set both xxxUser and xxxOwner
-        QFile file(xdgRuntimeDir);
         const QFile::Permissions wantedPerms = QFile::ReadUser | QFile::WriteUser | QFile::ExeUser
                                                | QFile::ReadOwner | QFile::WriteOwner | QFile::ExeOwner;
-        if (file.permissions() != wantedPerms && !file.setPermissions(wantedPerms)) {
+        if (fileInfo.permissions() != wantedPerms) {
+            QFile file(xdgRuntimeDir);
+            if (!file.setPermissions(wantedPerms)) {
                 qWarning("QStandardPaths: could not set correct permissions on runtime directory %s: %s",
                          qPrintable(xdgRuntimeDir), qPrintable(file.errorString()));
                 return QString();
             }
+        }
         return xdgRuntimeDir;
     }
     default:

tests/auto/corelib/io/qstandardpaths/tst_qstandardpaths.cpp

@@ -464,6 +464,15 @@ void tst_qstandardpaths::testCustomRuntimeDirectory()
 #endif
 
 #ifdef Q_XDG_PLATFORM
+    struct EnvVarRestorer
+    {
+        EnvVarRestorer() : origRuntimeDir(qgetenv("XDG_RUNTIME_DIR")) {}
+        ~EnvVarRestorer() { qputenv("XDG_RUNTIME_DIR", origRuntimeDir.constData()); }
+        const QByteArray origRuntimeDir;
+    };
+    EnvVarRestorer restorer;
+
+    // When $XDG_RUNTIME_DIR points to a directory with wrong ownership, QStandardPaths should warn
     qputenv("XDG_RUNTIME_DIR", QFile::encodeName("/tmp"));
     // It's very unlikely that /tmp is 0600 or that we can chmod it
     // The call below outputs
@@ -474,6 +483,20 @@ void tst_qstandardpaths::testCustomRuntimeDirectory()
             qPrintable(QString::fromLatin1("QStandardPaths: wrong ownership on runtime directory /tmp, 0 instead of %1").arg(uid)));
     const QString runtimeDir = QStandardPaths::writableLocation(QStandardPaths::RuntimeLocation);
     QVERIFY2(runtimeDir.isEmpty(), qPrintable(runtimeDir));
+
+    // When $XDG_RUNTIME_DIR points to a non-existing directory, QStandardPaths should warn (QTBUG-48771)
+    qputenv("XDG_RUNTIME_DIR", "does_not_exist");
+    QTest::ignoreMessage(QtWarningMsg, "QStandardPaths: XDG_RUNTIME_DIR points to non-existing path 'does_not_exist', please create it with 0700 permissions.");
+    const QString nonExistingRuntimeDir = QStandardPaths::writableLocation(QStandardPaths::RuntimeLocation);
+    QVERIFY2(nonExistingRuntimeDir.isEmpty(), qPrintable(nonExistingRuntimeDir));
+
+    // When $XDG_RUNTIME_DIR points to a file, QStandardPaths should warn
+    const QString file = QFINDTESTDATA("tst_qstandardpaths.cpp");
+    QVERIFY(!file.isEmpty());
+    qputenv("XDG_RUNTIME_DIR", QFile::encodeName(file));
+    QTest::ignoreMessage(QtWarningMsg, qPrintable(QString::fromLatin1("QStandardPaths: XDG_RUNTIME_DIR points to '%1' which is not a directory").arg(file)));
+    const QString noRuntimeDir = QStandardPaths::writableLocation(QStandardPaths::RuntimeLocation);
+    QVERIFY2(noRuntimeDir.isEmpty(), qPrintable(file));
 #endif
 }