QTest: rip out qxp::function_ref from reportResult()

This is causing huge code bloat because everything is a local lambda.
Instead, pass direct type-erased function and data pointers to the
replacement function. Testing with tst_qcborvalue, this reduces the
compilation time and the output binary size significantly:

                   Before                   After
Compiler        Time      Size          Time     Size
GCC 13.2        136.99 s  202.3 MB      13.88 s  14.3 MB
GCC 14.0        131.49 s  202.7 MB      14.69 s  14.4 MB
Clang 17        77.2 s    146.7 MB      13.62 s  12.2 MB
Clang 18        141.9 s   187.1 MB      13.62 s  12.4 MB

This causes a difference in how toString() overloads are
found. Previously it would match far more overloads because the
toString() calls were expanded by the macro. Now, we depend on
Argument-Dependent Lookup and associated namespaces, so toString()
overloads should not be in the QTest namespace any more.

With this patch applied, the testlib testcase of tst_selftest
started failing, because nullptr is now handled differently.
However, I consider it as a bugfix, because previously it was
falling back to a default implementation, and now it is using
the QTest::toString(std::nullptr_t) overload, which is a
desired behavior. Update the reference files for tst_selftest
with the new expected output.

Task-number: QTBUG-124272
Change-Id: Ie28eadac333c4bcd8c08fffd17c5484186accdf6
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>

7 files changed, 85 insertions, 25 deletions

diff --git a/src/testlib/qtest_network.h b/src/testlib/qtest_network.h
index 61f80a536c..403a663ae2 100644
--- a/src/testlib/qtest_network.h
+++ b/src/testlib/qtest_network.h
@@ -4,7 +4,7 @@
 #ifndef QTEST_NETWORK_H
 #define QTEST_NETWORK_H
 
-#include <QtTest/qtest.h>
+#include <QtTest/qtesttostring.h>
 
 // enable NETWORK features
 #ifndef QT_NETWORK_LIB
@@ -43,6 +43,7 @@ inline char *toString<QHostAddress>(const QHostAddress &addr)
 
     return toString(addr.toString());
 }
+} // namespace QTest
 
 inline char *toString(QNetworkReply::NetworkError code)
 {
@@ -57,7 +58,7 @@ inline char *toString(QNetworkReply::NetworkError code)
 
 inline char *toString(const QNetworkCookie &cookie)
 {
-    return toString(cookie.toRawForm());
+    return QTest::toString(cookie.toRawForm());
 }
 
 inline char *toString(const QList<QNetworkCookie> &list)
@@ -69,11 +70,9 @@ inline char *toString(const QList<QNetworkCookie> &list)
         result.chop(2); // remove trailing ", "
     }
     result.append(')');
-    return toString(result);
+    return QTest::toString(result);
 }
 
-} // namespace QTest
-
 QT_END_NAMESPACE
 
 #endif
diff --git a/src/testlib/qtest_widgets.h b/src/testlib/qtest_widgets.h
index 2b60d94fd7..90ee3aa6aa 100644
--- a/src/testlib/qtest_widgets.h
+++ b/src/testlib/qtest_widgets.h
@@ -62,15 +62,16 @@ inline QByteArray toString(QSizePolicy sp)
 }
 
 } // namespace Internal
+} // namespace QTest
 
 inline char *toString(QSizePolicy::Policy p)
 {
-    return qstrdup(Internal::toString(p));
+    return qstrdup(QTest::Internal::toString(p));
 }
 
 inline char *toString(QSizePolicy::ControlTypes ct)
 {
-    return qstrdup(Internal::toString(ct).constData());
+    return qstrdup(QTest::Internal::toString(ct).constData());
 }
 
 inline char *toString(QSizePolicy::ControlType ct)
@@ -80,11 +81,9 @@ inline char *toString(QSizePolicy::ControlType ct)
 
 inline char *toString(QSizePolicy sp)
 {
-    return qstrdup(Internal::toString(sp).constData());
+    return qstrdup(QTest::Internal::toString(sp).constData());
 }
 
-} // namespace QTest
-
 QT_END_NAMESPACE
 
 #endif
diff --git a/src/testlib/qtestcase.cpp b/src/testlib/qtestcase.cpp
index fb2b46d824..75c36066af 100644
--- a/src/testlib/qtestcase.cpp
+++ b/src/testlib/qtestcase.cpp
@@ -1745,14 +1745,33 @@ void TestMethods::invokeTests(QObject *testObject) const
     QSignalDumper::endDump();
 }
 
+#if QT_DEPRECATED_SINCE(6, 8)
+static const char *functionRefFormatter(const void *f)
+{
+    auto formatter = static_cast<const qxp::function_ref<const char *()> *>(f);
+    return (*formatter)();
+};
+
 bool reportResult(bool success, qxp::function_ref<const char *()> lhs,
                   qxp::function_ref<const char *()> rhs,
                   const char *lhsExpr, const char *rhsExpr,
                   ComparisonOperation op, const char *file, int line)
 {
-    return QTestResult::reportResult(success, lhs, rhs, lhsExpr, rhsExpr, op, file, line);
+    return QTestResult::reportResult(success, &lhs, &rhs,
+                                     functionRefFormatter, functionRefFormatter,
+                                     lhsExpr, rhsExpr, op, file, line);
 }
+#endif // QT_DEPRECATED_SINCE(6, 8)
 
+bool reportResult(bool success, const void *lhs, const void *rhs,
+                  const char *(*lhsFormatter)(const void*),
+                  const char *(*rhsFormatter)(const void*),
+                  const char *lhsExpr, const char *rhsExpr,
+                  ComparisonOperation op, const char *file, int line)
+{
+    return QTestResult::reportResult(success, lhs, rhs, lhsFormatter, rhsFormatter,
+                                     lhsExpr, rhsExpr, op, file, line);
+}
 } // namespace QTest
 
 static void initEnvironment()
@@ -2748,7 +2767,12 @@ bool QTest::compare_helper(bool success, const char *failureMsg,
                            const char *actual, const char *expected,
                            const char *file, int line)
 {
-    return QTestResult::reportResult(success, actualVal, expectedVal, actual, expected,
+    auto functionRefFormatter = [](const void *f) {
+        auto formatter = static_cast<const qxp::function_ref<const char *()> *>(f);
+        return (*formatter)();
+    };
+    return QTestResult::reportResult(success, &actualVal, &expectedVal, functionRefFormatter,
+                                     functionRefFormatter, actual, expected,
                                      QTest::ComparisonOperation::CustomCompare,
                                      file, line, failureMsg);
 }
diff --git a/src/testlib/qtestcase.h b/src/testlib/qtestcase.h
index 06fbd25c9c..6df20f8121 100644
--- a/src/testlib/qtestcase.h
+++ b/src/testlib/qtestcase.h
@@ -95,8 +95,7 @@ do { \
         return QTest::reportResult(std::forward<decltype(qt_lhs_arg)>(qt_lhs_arg) \
                                    op \
                                    std::forward<decltype(qt_rhs_arg)>(qt_rhs_arg), \
-                                   [&qt_lhs_arg] { return QTest::toString(qt_lhs_arg); }, \
-                                   [&qt_rhs_arg] { return QTest::toString(qt_rhs_arg); }, \
+                                   qt_lhs_arg, qt_rhs_arg, \
                                    #lhs, #rhs, QTest::ComparisonOperation::opId, \
                                    __FILE__, __LINE__); \
     }(lhs, rhs)) { \
@@ -330,6 +329,18 @@ namespace QTest
 
     Q_TESTLIB_EXPORT QString formatTryTimeoutDebugMessage(q_no_char8_t::QUtf8StringView expr, int timeout, int actual);
 
+    template <typename T1> const char *genericToString(const void *arg)
+    {
+        using QTest::toString;
+        return toString(*static_cast<const T1 *>(arg));
+    }
+
+    template <> inline const char *genericToString<char *>(const void *arg)
+    {
+        using QTest::toString;
+        return toString(static_cast<const char *>(arg));
+    }
+
     // Exported so Qt Quick Test can also use it for generating backtraces upon crashes.
     Q_TESTLIB_EXPORT extern bool noCrashHandler;
 
@@ -644,10 +655,32 @@ namespace QTest
                        qMetaTypeId<T>())), actualStr, expected, file, line);
     }
 
+#if QT_DEPRECATED_SINCE(6, 8)
+    QT_DEPRECATED_VERSION_X_6_8("use the overload without qxp::function_ref")
     Q_TESTLIB_EXPORT bool reportResult(bool success, qxp::function_ref<const char*()> lhs,
                                        qxp::function_ref<const char*()> rhs,
                                        const char *lhsExpr, const char *rhsExpr,
                                        ComparisonOperation op, const char *file, int line);
+#endif // QT_DEPRECATED_SINCE(6, 8)
+
+    Q_TESTLIB_EXPORT bool reportResult(bool success, const void *lhs, const void *rhs,
+                                       const char *(*lhsFormatter)(const void*),
+                                       const char *(*rhsFormatter)(const void*),
+                                       const char *lhsExpr, const char *rhsExpr,
+                                       ComparisonOperation op, const char *file, int line);
+
+    template <typename T1, typename T2>
+    inline bool reportResult(bool result, const T1 &lhs, const T2 &rhs,
+                             const char *lhsExpr, const char *rhsExpr,
+                             ComparisonOperation op, const char *file, int line)
+    {
+        using D1 = std::decay_t<T1>;
+        using D2 = std::decay_t<T2>;
+        using Internal::genericToString;
+        return reportResult(result, std::addressof(lhs), std::addressof(rhs),
+                            genericToString<D1>, genericToString<D2>,
+                            lhsExpr, rhsExpr, op, file, line);
+    }
 }
 
 
diff --git a/src/testlib/qtestcase.qdoc b/src/testlib/qtestcase.qdoc
index 973899e4d3..2eb060b9af 100644
--- a/src/testlib/qtestcase.qdoc
+++ b/src/testlib/qtestcase.qdoc
@@ -1608,7 +1608,8 @@
 */
 
 /*!
-    \fn char *QTest::toString(QSizePolicy::ControlType ct)
+    \fn char *toString(QSizePolicy::ControlType ct)
+    \relates QTest
     \overload
     \since 5.5
 
@@ -1616,7 +1617,8 @@
 */
 
 /*!
-    \fn char *QTest::toString(QSizePolicy::ControlTypes cts)
+    \fn char *toString(QSizePolicy::ControlTypes cts)
+    \relates QTest
     \overload
     \since 5.5
 
@@ -1624,7 +1626,8 @@
 */
 
 /*!
-    \fn char *QTest::toString(QSizePolicy::Policy p)
+    \fn char *toString(QSizePolicy::Policy p)
+    \relates QTest
     \overload
     \since 5.5
 
@@ -1632,7 +1635,8 @@
 */
 
 /*!
-    \fn char *QTest::toString(QSizePolicy sp)
+    \fn char *toString(QSizePolicy sp)
+    \relates QTest
     \overload
     \since 5.5
 
diff --git a/src/testlib/qtestresult.cpp b/src/testlib/qtestresult.cpp
index 093e9b58ef..7c5ce9ce54 100644
--- a/src/testlib/qtestresult.cpp
+++ b/src/testlib/qtestresult.cpp
@@ -628,8 +628,9 @@ static const char *failureMessageForOp(QTest::ComparisonOperation op)
     Q_UNREACHABLE_RETURN("");
 }
 
-bool QTestResult::reportResult(bool success, qxp::function_ref<const char *()> lhs,
-                               qxp::function_ref<const char *()> rhs,
+bool QTestResult::reportResult(bool success, const void *lhs, const void *rhs,
+                               const char *(*lhsFormatter)(const void*),
+                               const char *(*rhsFormatter)(const void*),
                                const char *lhsExpr, const char *rhsExpr,
                                QTest::ComparisonOperation op, const char *file, int line,
                                const char *failureMessage)
@@ -653,8 +654,8 @@ bool QTestResult::reportResult(bool success, qxp::function_ref<const char *()> l
         return checkStatement(success, msg, file, line);
     }
 
-    const std::unique_ptr<const char[]> lhsPtr{ lhs() };
-    const std::unique_ptr<const char[]> rhsPtr{ rhs() };
+    const std::unique_ptr<const char[]> lhsPtr{ lhsFormatter(lhs) };
+    const std::unique_ptr<const char[]> rhsPtr{ rhsFormatter(rhs) };
 
     if (!failureMessage)
         failureMessage = failureMessageForOp(op);
diff --git a/src/testlib/qtestresult_p.h b/src/testlib/qtestresult_p.h
index 48c2c34611..52607cc2ee 100644
--- a/src/testlib/qtestresult_p.h
+++ b/src/testlib/qtestresult_p.h
@@ -17,7 +17,6 @@
 
 #include <QtTest/qttestglobal.h>
 #include <QtCore/qstringfwd.h>
-#include <QtCore/qxpfunctional.h>
 #include <QtCore/private/qglobal_p.h>
 
 QT_BEGIN_NAMESPACE
@@ -102,8 +101,9 @@ public:
     static void setCurrentAppName(const char *appName);
     static const char *currentAppName();
 
-    static bool reportResult(bool success, qxp::function_ref<const char *()> lhs,
-                             qxp::function_ref<const char *()> rhs,
+    static bool reportResult(bool success, const void *lhs, const void *rhs,
+                             const char *(*lhsFormatter)(const void*),
+                             const char *(*rhsFormatter)(const void*),
                              const char *lhsExpr, const char *rhsExpr,
                              QTest::ComparisonOperation op, const char *file, int line,
                              const char *failureMessage = nullptr);