qt: add patches to fix SFINAE errors/warnings with gcc16

Meta-Issue: https://qt-project.atlassian.net/browse/QTBUG-143470 Backports: 679e8bda1e 3312e89b47 05f201a3d5 An additional includes fix is needed after the others: d68fc6ecc8 Github-Pull: #34650 Rebased-From: 3cb4d6066b83348411c43587605b624f067dbbf3
2026-03-15 07:52:39 +00:00 · 2026-02-12 18:34:02 +00:00 · 2026-02-12 18:34:02 +00:00 · 8f5c205aa9
commit 8f5c205aa9
parent b268b4b3d4
5 changed files with 296 additions and 1 deletions
--- a/depends/packages/qt.mk
+++ b/depends/packages/qt.mk
@ -21,6 +21,10 @@ $(package)_patches += qtbase_skip_tools.patch
 $(package)_patches += rcc_hardcode_timestamp.patch
 $(package)_patches += qttools_skip_dependencies.patch
 $(package)_patches += fix-gcc16-qcompare.patch
+$(package)_patches += fix-gcc16-sfinae-qregularexpression.patch
+$(package)_patches += fix-gcc16-sfinae-qchar.patch
+$(package)_patches += fix-gcc16-sfinae-qbitarray.patch
+$(package)_patches += fix-qbytearray-include.patch

 $(package)_qttranslations_file_name=$(qt_details_qttranslations_file_name)
 $(package)_qttranslations_sha256_hash=$(qt_details_qttranslations_sha256_hash)
@ -266,7 +270,11 @@ define $(package)_preprocess_cmds
  patch -p1 -i $($(package)_patch_dir)/qtbase_plugins_windows11style.patch && \
  patch -p1 -i $($(package)_patch_dir)/qtbase_skip_tools.patch && \
  patch -p1 -i $($(package)_patch_dir)/rcc_hardcode_timestamp.patch && \
-  patch -p1 -i $($(package)_patch_dir)/fix-gcc16-qcompare.patch
+  patch -p1 -i $($(package)_patch_dir)/fix-gcc16-qcompare.patch && \
+  patch -p1 -i $($(package)_patch_dir)/fix-gcc16-sfinae-qregularexpression.patch && \
+  patch -p1 -i $($(package)_patch_dir)/fix-gcc16-sfinae-qchar.patch && \
+  patch -p1 -i $($(package)_patch_dir)/fix-gcc16-sfinae-qbitarray.patch && \
+  patch -p1 -i $($(package)_patch_dir)/fix-qbytearray-include.patch
 endef
 ifeq ($(host),$(build))
  $(package)_preprocess_cmds += && patch -p1 -i $($(package)_patch_dir)/qttools_skip_dependencies.patch
--- a/depends/patches/qt/fix-gcc16-sfinae-qbitarray.patch
+++ b/depends/patches/qt/fix-gcc16-sfinae-qbitarray.patch
@ -0,0 +1,56 @@
+From 679e8bda1eb0cc98acb981e9a10204bed1c179f2 Mon Sep 17 00:00:00 2001
+From: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
+Date: Tue, 20 Jan 2026 15:23:31 +0100
+Subject: [PATCH] qhashfunctions.h: include QBitArray
+
+In qhashfunctions.h we're declaring a std::hash specialization for
+QBitArray. That specialization instantiates
+QNothrowHashable_v<QBitArray>, which checks if qHash(QBitArray) is
+noexcept.
+
+The problem is that there are already qHash(QByteArrayView) and
+qHash(QStringView) around, which will be picked up by overload
+resolution. That, in turn, will try to instantiate the QBAV/QSV
+constructors from a generic container. That instantiation will fail
+because QBitArray is not complete yet.
+
+When we later complete QBitArray, GCC is going to complain.
+
+Therefore, complete QBitArray before attempting SFINAE tricks on it.
+
+As an alternative, I could've moved the std::hash specialization
+to qbitarray.h. However I noticed that qHash(QBitArray) is still
+declared into qhashfunctions.h, i.e. hashing QBitArrays didn't
+require the full type, and therefore moving std::hash would've been
+a potential SIC?
+
+Task-number: QTBUG-143470
+Change-Id: Ie79d15e77d1fb3c86de6d7480a66bddc39f17666
+Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
+---
+ src/corelib/tools/qhashfunctions.h | 5 +++--
+ 1 file changed, 3 insertions(+), 2 deletions(-)
+
+diff --git a/qtbase/src/corelib/tools/qhashfunctions.h b/qtbase/src/corelib/tools/qhashfunctions.h
+index 8f1394c8ad35..beef80557865 100644
+--- a/qtbase/src/corelib/tools/qhashfunctions.h
+++ b/qtbase/src/corelib/tools/qhashfunctions.h
+@@ -7,6 +7,9 @@
+
+ #include <QtCore/qstring.h>
+ #include <QtCore/qstringfwd.h>
+#ifndef QT_BOOTSTRAPPED
+#include <QtCore/qbitarray.h>
+#endif
+
+ #include <numeric> // for std::accumulate
+ #include <functional> // for std::hash
+@@ -24,8 +27,6 @@
+
+ QT_BEGIN_NAMESPACE
+
+-class QBitArray;
+-
+ #if QT_DEPRECATED_SINCE(6,6)
+ QT_DEPRECATED_VERSION_X_6_6("Use QHashSeed instead")
+ Q_CORE_EXPORT int qGlobalQHashSeed();
--- a/depends/patches/qt/fix-gcc16-sfinae-qchar.patch
+++ b/depends/patches/qt/fix-gcc16-sfinae-qchar.patch
@ -0,0 +1,123 @@
+From 05f201a3d559452287b20becb960de3a50249540 Mon Sep 17 00:00:00 2001
+From: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
+Date: Wed, 4 Feb 2026 12:12:37 +0100
+Subject: [PATCH] Move QChar::fromUcs4 into qchar.h
+
+Right now fromUcs4 lives in qstringview.h because the return type has an
+implicit conversion operator towards QStringView. This however creates
+an inclusion loop: qchar.h includes qstringview.h, and qstringview.h
+includes qchar.h. Only the latter should exist.
+
+We can move the code back into qchar.h and drop the QStringView
+dependency by making the type returned from fromUcs4 have data(). That
+would make it a string-like range and become implicitly convertible to
+QStringView through its ranged constructor.
+
+In fact, add a test that checks for the *implicit* conversion; and
+add a test that checks for a conversion towards std::u16string_view.
+
+QMetaType was calling the conversion operator from the return type of
+fromUcs4 to QStringView directly (...Hyrum law...), although we never
+documented the presence of that operator, only that the conversion was
+possible; fix it by using a conversion.
+
+Fixes: QTBUG-143873
+Task-number: QTBUG-143470
+Change-Id: Id07657dd411cc2e1446fb18789e04db9cecd8ae0
+Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
+Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
+
+
+diff --git a/qtbase/src/corelib/text/qchar.h b/qtbase/src/corelib/text/qchar.h
+index 4a3aad0ca0c1..f96ca590f2e2 100644
+--- a/qtbase/src/corelib/text/qchar.h
+++ b/qtbase/src/corelib/text/qchar.h
+@@ -96,7 +96,19 @@ public:
+ #undef QCHAR_MAYBE_IMPLICIT
+ 
+     static constexpr QChar fromUcs2(char16_t c) noexcept { return QChar{c}; }
+-    static constexpr inline auto fromUcs4(char32_t c) noexcept;
+    [[nodiscard]] static constexpr inline auto fromUcs4(char32_t c) noexcept
+    {
+        struct R {
+            char16_t chars[2];
+            [[nodiscard]] constexpr qsizetype size() const noexcept { return chars[1] ? 2 : 1; }
+            [[nodiscard]] constexpr const char16_t *data() const noexcept { return chars; }
+            [[nodiscard]] constexpr const char16_t *begin() const noexcept { return chars; }
+            [[nodiscard]] constexpr const char16_t *end() const noexcept { return begin() + size(); }
+        };
+        return requiresSurrogates(c) ? R{{QChar::highSurrogate(c),
+                                          QChar::lowSurrogate(c)}} :
+                                       R{{char16_t(c), u'\0'}} ;
+    }
+ 
+     // Unicode information
+ 
+@@ -652,5 +664,3 @@ struct hash<QT_PREPEND_NAMESPACE(QChar)>
+ } // namespace std
+
+ #endif // QCHAR_H
+-
+-#include <QtCore/qstringview.h> // for QChar::fromUcs4() definition
+diff --git a/qtbase/src/corelib/text/qstringview.h b/qtbase/src/corelib/text/qstringview.h
+index 6d5edfc06d7d..d5897af6da2d 100644
+--- a/qtbase/src/corelib/text/qstringview.h
+++ b/qtbase/src/corelib/text/qstringview.h
+@@ -444,22 +444,6 @@ template <typename QStringLike, typename std::enable_if<
+ inline QStringView qToStringViewIgnoringNull(const QStringLike &s) noexcept
+ { return QStringView(s.data(), s.size()); }
+ 
+-// QChar inline functions:
+-
+-[[nodiscard]] constexpr auto QChar::fromUcs4(char32_t c) noexcept
+-{
+-    struct R {
+-        char16_t chars[2];
+-        [[nodiscard]] constexpr operator QStringView() const noexcept { return {begin(), end()}; }
+-        [[nodiscard]] constexpr qsizetype size() const noexcept { return chars[1] ? 2 : 1; }
+-        [[nodiscard]] constexpr const char16_t *begin() const noexcept { return chars; }
+-        [[nodiscard]] constexpr const char16_t *end() const noexcept { return begin() + size(); }
+-    };
+-    return requiresSurrogates(c) ? R{{QChar::highSurrogate(c),
+-                                      QChar::lowSurrogate(c)}} :
+-                                   R{{char16_t(c), u'\0'}} ;
+-}
+-
+ QT_END_NAMESPACE
+ 
+ #endif /* QSTRINGVIEW_H */
+diff --git a/qtbase/tests/auto/corelib/text/qchar/tst_qchar.cpp b/qtbase/tests/auto/corelib/text/qchar/tst_qchar.cpp
+index 6701f0e33f3d..5781d36e458b 100644
+--- a/qtbase/tests/auto/corelib/text/qchar/tst_qchar.cpp
+++ b/qtbase/tests/auto/corelib/text/qchar/tst_qchar.cpp
+@@ -80,10 +80,20 @@ void tst_QChar::fromUcs4()
+         QCOMPARE(result.chars[0], QChar::highSurrogate(ucs4));
+         QCOMPARE(result.chars[1], QChar::lowSurrogate(ucs4));
+         QCOMPARE(QStringView{result}.size(), 2);
+        QStringView v = result;
+        QCOMPARE(v.size(), 2);
+#if __cplusplus >= 202302L // no FTM for the ranged constructor of basic_string_view
+        QCOMPARE(std::u16string_view{result}.size(), 2);
+#endif
+     } else {
+         QCOMPARE(result.chars[0], ucs4);
+         QCOMPARE(result.chars[1], 0u);
+         QCOMPARE(QStringView{result}.size(), 1);
+        QStringView v = result;
+        QCOMPARE(v.size(), 1);
+#if __cplusplus >= 202302L // no FTM for the ranged constructor of basic_string_view
+        QCOMPARE(std::u16string_view{result}.size(), 1);
+#endif
+     }
+ }
+
+--- a/qtbase/src/corelib/serialization/qtextstream.h
+++ b/qtbase/src/corelib/serialization/qtextstream.h
+@@ -6,6 +6,7 @@
+ 
+ #include <QtCore/qiodevicebase.h>
+ #include <QtCore/qchar.h>
+#include <QtCore/qlatin1stringview.h>
+ #include <QtCore/qscopedpointer.h>
+ #include <QtCore/qstringconverter_base.h>
+ 
--- a/depends/patches/qt/fix-gcc16-sfinae-qregularexpression.patch
+++ b/depends/patches/qt/fix-gcc16-sfinae-qregularexpression.patch
@ -0,0 +1,68 @@
+From 3312e89b47f8c2ea0b4263b39841c25b83a37332 Mon Sep 17 00:00:00 2001
+From: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
+Date: Fri, 16 Jan 2026 21:54:45 +0100
+Subject: [PATCH] QStringView: fix benign ODR violation for
+ count(QRegularExpression)
+
+QRegularExpression is only forward declared in qstringview.h.
+QStringView::count(const QRegularExpression &re) simply calls
+`QtPrivate::count(*this, re)`. The problem is that this latter
+count is overloaded, and there's a `QtPrivate::count(QStringView,
+QStringView)` overload available.
+
+This overload is not viable because there is no conversion from
+QRegularExpression to QStringView. To determine this, the compiler
+instantiates the QStringView(const Container &) constructor template,
+with Container = QRegularExpression. This function template is
+constrained via SFINAE, and it will fail the constraint checks
+_because QRegularExpression is incomplete_ (in particular std::data
+itself has SFINAE, and it fails in there).
+
+GCC doesn't like the idea that at a later time we complete
+QRegularExpression, because it fears that the prior result might
+have been different had QRegularExpression been complete.
+
+We know it's not different, but still, silence the warning by
+moving the call to QtPrivate::count where QRegularExpression
+is complete.
+
+Pick-to: 6.11
+Change-Id: I294c5ccb7c4ab3d52e518182c159e690575cbb00
+Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
+---
+ src/corelib/text/qregularexpression.h | 5 +++++
+ src/corelib/text/qstringview.h        | 5 +----
+ 2 files changed, 6 insertions(+), 4 deletions(-)
+
+diff --git a/qtbase/src/corelib/text/qregularexpression.h b/qtbase/src/corelib/text/qregularexpression.h
+index 462786179cb5..ece094ca768f 100644
+--- a/qtbase/src/corelib/text/qregularexpression.h
+++ b/qtbase/src/corelib/text/qregularexpression.h
+@@ -187,6 +187,11 @@ Q_CORE_EXPORT QDebug operator<<(QDebug debug, const QRegularExpression &re);
+ Q_CORE_EXPORT QDebug operator<<(QDebug debug, QRegularExpression::PatternOptions patternOptions);
+ #endif
+
+[[nodiscard]] inline qsizetype QStringView::count(const QRegularExpression &re) const
+{
+    return QtPrivate::count(*this, re);
+}
+
+ struct QRegularExpressionMatchPrivate;
+ QT_DECLARE_QESDP_SPECIALIZATION_DTOR_WITH_EXPORT(QRegularExpressionMatchPrivate, Q_CORE_EXPORT)
+
+diff --git a/qtbase/src/corelib/text/qstringview.h b/qtbase/src/corelib/text/qstringview.h
+index d586620c8b09..6d5edfc06d7d 100644
+--- a/qtbase/src/corelib/text/qstringview.h
+++ b/qtbase/src/corelib/text/qstringview.h
+@@ -321,10 +321,7 @@ class QStringView
+     {
+         return QtPrivate::contains(*this, re, rmatch);
+     }
+-    [[nodiscard]] qsizetype count(const QRegularExpression &re) const
+-    {
+-        return QtPrivate::count(*this, re);
+-    }
+    [[nodiscard]] qsizetype count(const QRegularExpression &re) const; // defined in qregularexpression.h
+ #endif
+
+     [[nodiscard]] bool isRightToLeft() const noexcept
--- a/depends/patches/qt/fix-qbytearray-include.patch
+++ b/depends/patches/qt/fix-qbytearray-include.patch
@ -0,0 +1,40 @@
+From d68fc6ecc88a0e4532754b1a9f209881a248f4ee Mon Sep 17 00:00:00 2001
+From: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
+Date: Wed, 4 Feb 2026 12:33:08 +0100
+Subject: [PATCH] QByteArrayView: include qchar.h
+
+QByteArrayView needs the complete definition of QChar in order to
+define its relational operators against it.
+
+In particular, the expansion of the
+
+Q_DECLARE_STRONGLY_ORDERED(QByteArrayView, QChar, QT_ASCII_CAST_WARN)
+
+macro creates an overload set where the QByteArrayView(Container)
+constructor is considered. GCC complains that that constructor is
+excluded via SFINAE for Container = QChar, not because QChar isn't a
+suitable container (indeed, it's not), but because it's *incomplete* at
+that point. When QChar is later completed, GCC is afraid that the
+previous substitution failure might have yielded a different result,
+and warns about it. Fix this by including QChar.
+
+Task-number: QTBUG-143470
+Change-Id: I705f91ef1133b59363df0cd6dbab91a5854e248c
+Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
+Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
+---
+ src/corelib/text/qbytearrayview.h | 1 +
+ 1 file changed, 1 insertion(+)
+
+diff --git a/qtbase/src/corelib/text/qbytearrayview.h b/qtbase/src/corelib/text/qbytearrayview.h
+index 7d3e82e72a02..b19f6fd5424e 100644
+--- a/qtbase/src/corelib/text/qbytearrayview.h
+++ b/qtbase/src/corelib/text/qbytearrayview.h
+@@ -4,6 +4,7 @@
+ #define QBYTEARRAYVIEW_H
+ 
+ #include <QtCore/qbytearrayalgorithms.h>
+#include <QtCore/qchar.h>
+ #include <QtCore/qstringfwd.h>
+ #include <QtCore/qarraydata.h>
+