Localization: make cache thread safe and robust against use-after-free

The old trGettext() was not thread-safe and the returned C-strings
could be freed in the case of empty translations strings. Therefore:

1) Introduce a mutex protecting access to the cache.

2) Never change existing entries, even if the translation string is empty.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

1 files changed, 8 insertions, 4 deletions

diff --git a/core/gettextfromc.cpp b/core/gettextfromc.cpp
index fdb1e6d37..c3a592f5b 100644
--- a/core/gettextfromc.cpp
+++ b/core/gettextfromc.cpp
@@ -1,13 +1,17 @@
 // SPDX-License-Identifier: GPL-2.0
 #include "gettextfromc.h"
 #include <QHash>
+#include <QMutex>
 
 static QHash<QByteArray, QByteArray> translationCache;
+static QMutex lock;
 
 extern "C" const char *trGettext(const char *text)
 {
-	QByteArray &result = translationCache[QByteArray(text)];
-	if (result.isEmpty())
-		result = gettextFromC::tr(text).toUtf8();
-	return result.constData();
+	QByteArray key(text);
+	QMutexLocker l(&lock);
+	auto it = translationCache.find(key);
+	if (it == translationCache.end())
+		it = translationCache.insert(key, gettextFromC::tr(text).toUtf8());
+	return it->constData();
 }