From 457e6f8b199ae321ae74507d5ef2a3940279e54c Mon Sep 17 00:00:00 2001
From: Thiago Macieira <thiago.macieira@intel.com>
Date: Wed, 4 Oct 2023 09:25:29 -0700
Subject: [PATCH] Work around GCC 13's bogus "out of bounds" check to
 QByteArray::_empty
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Nothing here is empty and even if anything were, QStringBuilder properly
handles empty strings.

In static member function ‘static void QConcatenable<QByteArrayView>::appendTo(QByteArrayView, char*&)’,
    inlined from ‘static void QConcatenable<QStringBuilder< <template-parameter-1-1>, <template-parameter-1-2> > >::appendTo(const type&, T*&) [with T = char; A = QByteArrayView; B = const char (&)[20]]’ at qstringbuilder.h:398:37,
    inlined from ‘T QStringBuilder< <template-parameter-1-1>, <template-parameter-1-2> >::convertTo() const [with T = QByteArray; A = QByteArrayView; B = const char (&)[20]]’ at qstringbuilder.h:117:54,
    ...
qstringbuilder.h:178:19: error: ‘void* memcpy(void*, const void*, size_t)’ forming offset [1, 5] is out of the bounds [0, 1] of object ‘QByteArray::_empty’ with type ‘const char’ [-Werror=array-bounds=]

QStringBuilder::convertTo() creates the target as
        const qsizetype len = QConcatenable< QStringBuilder<A, B> >::size(*this);
        T s(len, Qt::Uninitialized);

We know len can't be zero because GCC is complaining about a memcpy()
when the offset has been changed from 0, meaning QByteArray was given a
non-zero size and therefore its data pointer is not &QByteArray::_empty.

Fixes: QTBUG-116763
Pick-to: 6.5
Change-Id: I85599ea5ca7a4b79a8bbfffd178af437984080fb
Reviewed-by: Shawn Rutledge (away) <shawn.rutledge@qt.io>
(cherry picked from commit 9aaf12ebaadf25db67932d6985d9aed424873d50)
Reviewed-by: Ahmad Samir <a.samirh78@gmail.com>
---
 src/gui/image/qimagereaderwriterhelpers.cpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/gui/image/qimagereaderwriterhelpers.cpp b/src/gui/image/qimagereaderwriterhelpers.cpp
index 1255cd827ac..24dc9c26431 100644
--- a/src/gui/image/qimagereaderwriterhelpers.cpp
+++ b/src/gui/image/qimagereaderwriterhelpers.cpp
@@ -97,6 +97,8 @@ QList<QByteArray> supportedImageFormats(Capability cap)
     return formats;
 }
 
+QT_WARNING_PUSH
+QT_WARNING_DISABLE_GCC("-Warray-bounds") // QTBUG-116763
 QList<QByteArray> supportedMimeTypes(Capability cap)
 {
     QList<QByteArray> mimeTypes;
@@ -112,6 +114,7 @@ QList<QByteArray> supportedMimeTypes(Capability cap)
     mimeTypes.erase(std::unique(mimeTypes.begin(), mimeTypes.end()), mimeTypes.end());
     return mimeTypes;
 }
+QT_WARNING_POP
 
 QList<QByteArray> imageFormatsForMimeType(const QByteArray &mimeType, Capability cap)
 {