QPdfDocument: make code locale-independent

The C toupper/tolower functions are locale-dependent. Given the right
locale (Türkiye, e.g.), tolower(I) is either

- ı (LATIN SMALL LETTER DOTLESS I; if representable in current charset)
- I (unchanged; if it isn't)

Both results are wrong for the present use-case, so use US-ASCII-only
QtMiscUtils::toAsciiLower() to side-step the issue.

Besides, feeding unfiltered char values into tolower() is UB. You'd
first have to cast to uchar:
https://en.cppreference.com/w/cpp/string/byte/tolower

Task-number: QTBUG-109235
Change-Id: I57887581ba2e548e978223337d681124b30bf754
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
(cherry picked from commit 3172695838372b54c2a488975578eaedaf094e80)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

1 files changed, 3 insertions, 1 deletions

diff --git a/src/pdf/qpdfdocument.cpp b/src/pdf/qpdfdocument.cpp
index 9b8d20d3b..a3e412c5c 100644
--- a/src/pdf/qpdfdocument.cpp
+++ b/src/pdf/qpdfdocument.cpp
@@ -17,6 +17,8 @@
 #include <QMutex>
 #include <QVector2D>
 
+#include <QtCore/private/qtools_p.h>
+
 QT_BEGIN_NAMESPACE
 
 Q_GLOBAL_STATIC(QRecursiveMutex, pdfMutex)
@@ -39,7 +41,7 @@ public:
         QMetaEnum rolesMetaEnum = doc->metaObject()->enumerator(doc->metaObject()->indexOfEnumerator("PageModelRole"));
         for (int r = Qt::UserRole; r < int(QPdfDocument::PageModelRole::NRoles); ++r) {
             auto name = QByteArray(rolesMetaEnum.valueToKey(r));
-            name[0] = tolower(name[0]);
+            name[0] = QtMiscUtils::toAsciiLower(name[0]);
             m_roleNames.insert(r, name);
         }
         connect(doc, &QPdfDocument::statusChanged, this, [this](QPdfDocument::Status s) {