From 8a768fe7db6ac5388fec6a68687817796b44439e Mon Sep 17 00:00:00 2001
From: Thiago Macieira <thiago.macieira@intel.com>
Date: Tue, 23 Jul 2024 15:35:46 -0700
Subject: [PATCH] QOffsetStringArray: fix off-by-one error for the past-the-end
 elements

For legacy reasons, the accessor class allows operator[] to go out of
bounds and just returns an empty string. However, we were returning a
pointer to the one-past-end of the array, which appears to have been a
null byte in the test.

Instead of adding branching code to load the length of the first string
in operator[], we can just add an extra null character at the position
we were returning anyway.

Pick-to: 6.8 6.5
Change-Id: I4878533dcb2d4b3e8efefffd17e4f876b43e9ee3
Reviewed-by: Ahmad Samir <a.samirh78@gmail.com>
---
 src/corelib/tools/qoffsetstringarray_p.h                    | 3 ++-
 .../tools/qoffsetstringarray/tst_qoffsetstringarray.cpp     | 6 +++---
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/corelib/tools/qoffsetstringarray_p.h b/src/corelib/tools/qoffsetstringarray_p.h
index c3392789c7a..a4ef8a3e48f 100644
--- a/src/corelib/tools/qoffsetstringarray_p.h
+++ b/src/corelib/tools/qoffsetstringarray_p.h
@@ -96,7 +96,8 @@ template <size_t Highest> constexpr auto minifyValue()
 template <size_t StringLength, typename Extractor, typename... T>
 constexpr auto makeStaticString(Extractor extract, const T &... entries)
 {
-    std::array<char, StringLength> result = {};
+    // append an extra null terminator
+    std::array<char, StringLength + 1> result = {};
     qptrdiff offset = 0;
 
     const char *strings[] = { extract(entries).operator const char *()... };
diff --git a/tests/auto/corelib/tools/qoffsetstringarray/tst_qoffsetstringarray.cpp b/tests/auto/corelib/tools/qoffsetstringarray/tst_qoffsetstringarray.cpp
index dbb24e7af45..3265a9d9979 100644
--- a/tests/auto/corelib/tools/qoffsetstringarray/tst_qoffsetstringarray.cpp
+++ b/tests/auto/corelib/tools/qoffsetstringarray/tst_qoffsetstringarray.cpp
@@ -65,16 +65,16 @@ constexpr const auto messagesBigOffsets = qOffsetStringArray(
 
 void tst_QOffsetStringArray::init()
 {
-    static_assert(messages.m_string.size() == 50);
+    static_assert(messages.m_string.size() == 51);
     static_assert(messages.m_offsets.size() == 6);
     static_assert(std::is_same_v<decltype(messages.m_offsets)::value_type, quint8>);
 
     static_assert(messages257.m_offsets.size() == 258);
-    static_assert(messages257.m_string.size() == 260);
+    static_assert(messages257.m_string.size() == 261);
     static_assert(std::is_same_v<decltype(messages257.m_offsets)::value_type, quint16>);
 
     static_assert(messagesBigOffsets.m_offsets.size() == 5);
-    static_assert(messagesBigOffsets.m_string.size() == 364);
+    static_assert(messagesBigOffsets.m_string.size() == 365);
     static_assert(std::is_same_v<decltype(messagesBigOffsets.m_offsets)::value_type, quint16>);
 }