QStringBuilder: do not crash with null char*

This is supported by the others operator+

Change-Id: I9a1d1a0afb63acf32935948111d43ca6da370363
Reviewed-on: http://codereview.qt.nokia.com/764
Reviewed-by: hjk
(cherry picked from commit 53a16752c257d2f4f99ecef2cde1580b817fc12a)

2 files changed, 4 insertions, 0 deletions

diff --git a/src/corelib/tools/qstringbuilder.cpp b/src/corelib/tools/qstringbuilder.cpp
index 45de6bc..1cc7e5d 100644
--- a/src/corelib/tools/qstringbuilder.cpp
+++ b/src/corelib/tools/qstringbuilder.cpp
@@ -162,6 +162,8 @@ void QAbstractConcatenable::convertFromAscii(const char *a, int len, QChar *&out
     }
 #endif
     if (len == -1) {
+        if (!a)
+            return;
         while (*a)
             *out++ = QLatin1Char(*a++);
     } else {
diff --git a/src/corelib/tools/qstringbuilder.h b/src/corelib/tools/qstringbuilder.h
index 709d84a..594ab2f 100644
--- a/src/corelib/tools/qstringbuilder.h
+++ b/src/corelib/tools/qstringbuilder.h
@@ -352,6 +352,8 @@ template <> struct QConcatenable<const char *> : private QAbstractConcatenable
 #endif
     static inline void appendTo(const char *a, char *&out)
     {
+        if (!a)
+            return;
         while (*a)
             *out++ = *a++;
     }