From 5302857f5a716037aaef22143ea11102ad47bce0 Mon Sep 17 00:00:00 2001
From: Thiago Macieira <thiago.macieira@intel.com>
Date: Mon, 25 Apr 2022 14:00:58 -0700
Subject: [PATCH] Atomics: workaround GCC 12 warning about overflowing d->state
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I don't see a way this can be anything but a bogus warning.

In member function ‘std::__atomic_base<_IntTp>::__int_type std::__atomic_base<_IntTp>::fetch_or(__int_type, std::memory_order) [with _ITp = int]’,
    inlined from ‘static T QAtomicOps<X>::fetchAndOrRelaxed(std::atomic<T>&, typename QAtomicAdditiveType<T>::AdditiveT) [with T = int; X = int]’ at qatomic_cxx11.h:449:33,
    inlined from ‘T QBasicAtomicInteger<T>::fetchAndOrRelaxed(T) [with T = int]’ at qbasicatomic.h:168:36,
    inlined from ‘int switch_on(QAtomicInt&, int)’ at qfutureinterface.cpp:97:31,
    inlined from ‘void QFutureInterfaceBase::setThrottled(bool)’ at qfutureinterface.cpp:194:18:
atomic_base.h:648:33: warning: ‘unsigned int __atomic_or_fetch_4(volatile void*, unsigned int, int)’ writing 4 bytes into a region of size 0 overflows the destination [-Wstringop-overflow=]

A few more of those appear in other modules. I'm not fixing them all,
assuming GCC will soon fix the warning.

Pick-to: 6.2 6.3
Change-Id: I7fb65b80b7844c8d8f26fffd16e93f68e278d048
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
---
 src/corelib/thread/qfutureinterface.cpp | 5 +++++
 src/gui/text/qtextengine.cpp            | 7 +++++++
 2 files changed, 12 insertions(+)

diff --git a/src/corelib/thread/qfutureinterface.cpp b/src/corelib/thread/qfutureinterface.cpp
index efbcf9ce583..84d6b09ce8d 100644
--- a/src/corelib/thread/qfutureinterface.cpp
+++ b/src/corelib/thread/qfutureinterface.cpp
@@ -50,6 +50,11 @@
 #  undef interface
 #endif
 
+// GCC 12 gets confused about QFutureInterfaceBase::state, for some non-obvious
+// reason
+//  warning: ‘unsigned int __atomic_or_fetch_4(volatile void*, unsigned int, int)’ writing 4 bytes into a region of size 0 overflows the destination [-Wstringop-overflow=]
+QT_WARNING_DISABLE_GCC("-Wstringop-overflow")
+
 QT_BEGIN_NAMESPACE
 
 enum {
diff --git a/src/gui/text/qtextengine.cpp b/src/gui/text/qtextengine.cpp
index c7e5c19c31f..37388750ff0 100644
--- a/src/gui/text/qtextengine.cpp
+++ b/src/gui/text/qtextengine.cpp
@@ -2277,6 +2277,12 @@ QFontEngine *QTextEngine::fontEngine(const QScriptItem &si, QFixed *ascent, QFix
             if (feCache.prevScaledFontEngine) {
                 scaledEngine = feCache.prevScaledFontEngine;
             } else {
+                // GCC 12 gets confused about QFontEngine::ref, for some non-obvious reason
+                //  warning: ‘unsigned int __atomic_or_fetch_4(volatile void*, unsigned int, int)’ writing 4 bytes
+                //  into a region of size 0 overflows the destination [-Wstringop-overflow=]
+                QT_WARNING_PUSH
+                QT_WARNING_DISABLE_GCC("-Wstringop-overflow")
+
                 QFontEngine *scEngine = rawFont.d->fontEngine->cloneWithSize(smallCapsFraction * rawFont.pixelSize());
                 scEngine->ref.ref();
                 scaledEngine = QFontEngineMulti::createMultiFontEngine(scEngine, script);
@@ -2286,6 +2292,7 @@ QFontEngine *QTextEngine::fontEngine(const QScriptItem &si, QFixed *ascent, QFix
                 if (!scEngine->ref.deref())
                     delete scEngine;
 
+                QT_WARNING_POP
             }
         }
     } else