1 files changed, 6 insertions, 0 deletions
diff --git a/src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm b/src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm
index 2553cabe2b..4e50d6c53f 100644
--- a/src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm
+++ b/src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm
@@ -195,6 +195,12 @@ void QCoreTextFontEngine::init()
 bool QCoreTextFontEngine::stringToCMap(const QChar *str, int len, QGlyphLayout *glyphs,
                                        int *nglyphs, QFontEngine::ShaperFlags flags) const
 {
+    Q_ASSERT(glyphs->numGlyphs >= *nglyphs);
+    if (*nglyphs < len) {
+        *nglyphs = len;
+        return false;
+    }
+
     QVarLengthArray<CGGlyph> cgGlyphs(len);
     CTFontGetGlyphsForCharacters(ctfont, (const UniChar*)str, cgGlyphs.data(), len);