From 05b9a4b2deefd586356e1f36d84372b06e74cfe3 Mon Sep 17 00:00:00 2001
From: Marc Mutz <marc.mutz@qt.io>
Date: Tue, 24 Dec 2024 13:39:25 +0100
Subject: [PATCH] tst_QSpan: check QList<int> -> QSpan<const int> doesn't
 detach the former

It does.

While std::span, does, too, and so users should be using
std::as_const(), it's quite simple to avoid for QSpan, so we'll fix it
in QSpan. This patch adds the reproducer.

Task-number: QTBUG-132133
Pick-to: 6.9 6.8
Change-Id: I2e416fb7344830cd5e0d945cce61491cd6f4a7a5
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
---
 tests/auto/corelib/tools/qspan/tst_qspan.cpp | 28 ++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/tests/auto/corelib/tools/qspan/tst_qspan.cpp b/tests/auto/corelib/tools/qspan/tst_qspan.cpp
index 07dda7db85c..2d63b0a45a2 100644
--- a/tests/auto/corelib/tools/qspan/tst_qspan.cpp
+++ b/tests/auto/corelib/tools/qspan/tst_qspan.cpp
@@ -129,6 +129,8 @@ private Q_SLOTS:
     void fromQList() const;
     void fromInitList() const;
 
+    void constQSpansDontDetachQtContainers() const;
+
 private:
     template <typename T, std::size_t N, typename S, std::size_t M>
     void check_identical(QSpan<T, N> lhs, QSpan<S, M> rhs) const;
@@ -468,6 +470,32 @@ void tst_QSpan::fromQList() const
     from_variable_size_container_impl(li);
 }
 
+void tst_QSpan::constQSpansDontDetachQtContainers() const
+{
+    QList<int> li = {42, 84, 168, 336};
+
+    {
+        [[maybe_unused]] const QList copy = li;
+        QVERIFY(!li.isDetached());
+        [[maybe_unused]] QSpan<const int> cvspan = li; // should not detach (QTBUG-132133)
+        QEXPECT_FAIL("", "QTBUG-132133", Continue);
+        QVERIFY(!li.isDetached());
+        [[maybe_unused]] QSpan<int> mvspan = li; // this _has_ to detach, though
+        QVERIFY(li.isDetached());
+    }
+
+    // same check for fixed-size spans
+    {
+        [[maybe_unused]] const QList copy = li;
+        QVERIFY(!li.isDetached());
+        [[maybe_unused]] QSpan<const int, 4> cfspan = li; // should not detach (QTBUG-132133)
+        QEXPECT_FAIL("", "QTBUG-132133", Continue);
+        QVERIFY(!li.isDetached());
+        [[maybe_unused]] QSpan<int, 4> mfspan = li; // this _has_ to detach, though
+        QVERIFY(li.isDetached());
+    }
+}
+
 void tst_QSpan::fromInitList() const
 {
     from_variable_size_container_impl(std::initializer_list<int>{42, 84, 168, 336});