Ensure left/right/mid behave in a compatible way

QString and QStringRef did bounds checking for left/right/mid, whereas
QStringView was asserting on out of bounds.

Relax the behavior for QStringView and do bounds checking on pos/n
as well. This removes a source of potentially hidden errors when porting
from QStringRef (or QString) to QStringView.

Unfortunately, one difference remains, where QByteArray::left/right()
behaves differently (and somewhat more sane) than QString and
QStringRef. We're keeping the difference here, as it has been around
for many years.

Mark left/right/mid as obsolete and to be replaced with the new
first/last/slice methods.

Change-Id: I18c203799ba78c928a4610a6038089f27696c22e
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

1 files changed, 5 insertions, 3 deletions

diff --git a/src/corelib/tools/qvector.h b/src/corelib/tools/qvector.h
index c2cdcba41d..b502a86442 100644
--- a/src/corelib/tools/qvector.h
+++ b/src/corelib/tools/qvector.h
@@ -710,8 +710,10 @@ int QVector<T>::lastIndexOf(const T &t, int from) const noexcept
 template <typename T>
 inline QVector<T> QVector<T>::mid(int pos, int len) const
 {
+    qsizetype p = pos;
+    qsizetype l = len;
     using namespace QtPrivate;
-    switch (QContainerImplHelper::mid(d.size, &pos, &len)) {
+    switch (QContainerImplHelper::mid(d.size, &p, &l)) {
     case QContainerImplHelper::Null:
     case QContainerImplHelper::Empty:
         return QVector();
@@ -722,8 +724,8 @@ inline QVector<T> QVector<T>::mid(int pos, int len) const
     }
 
     // Allocate memory
-    DataPointer copied(Data::allocate(len));
-    copied->copyAppend(constBegin() + pos, constBegin() + pos + len);
+    DataPointer copied(Data::allocate(l));
+    copied->copyAppend(constBegin() + p, constBegin() + p + l);
     return copied;
 }