Prevent an overflow warning in assertions.

Functions like QByteArray::at() assert the given index:
    Q_ASSERT(i >= 0 && i < size();
These functions typically get inlined. Now if the index is
e.g. size() - 2, then gcc will emit an ugly warning in
client code ("assuming signed overflow does not occur when assuming
that (X - c) > X is always false").
This can be easily prevented by casting both sides of the second
comparison in the assertion to their unsigned type. The explicit
comparison to zero is then no longer necessary, since that condition
is tested implicitly by the other comparison due to unsigned arithmetic.

Change-Id: Ic7244e1fa5da00a47d1fe0ed56fb81c23d444dfe
Reviewed-by: hjk <qthjk@ovi.com>
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
(cherry picked from qtbase/8e90e0805f2981014d3382d8841617b4c56dfc50)

3 files changed, 7 insertions, 7 deletions

diff --git a/src/corelib/tools/qbitarray.h b/src/corelib/tools/qbitarray.h
index 3e9ab3182f..e0e968c8d5 100644
--- a/src/corelib/tools/qbitarray.h
+++ b/src/corelib/tools/qbitarray.h
@@ -122,22 +122,22 @@ Q_CORE_EXPORT QBitArray operator|(const QBitArray &, const QBitArray &);
 Q_CORE_EXPORT QBitArray operator^(const QBitArray &, const QBitArray &);
 
 inline bool QBitArray::testBit(int i) const
-{ Q_ASSERT(i >= 0 && i < size());
+{ Q_ASSERT(uint(i) < uint(size()));
  return (*(reinterpret_cast<const uchar*>(d.constData())+1+(i>>3)) & (1 << (i & 7))) != 0; }
 
 inline void QBitArray::setBit(int i)
-{ Q_ASSERT(i >= 0 && i < size());
+{ Q_ASSERT(uint(i) < uint(size()));
  *(reinterpret_cast<uchar*>(d.data())+1+(i>>3)) |= uchar(1 << (i & 7)); }
 
 inline void QBitArray::clearBit(int i)
-{ Q_ASSERT(i >= 0 && i < size());
+{ Q_ASSERT(uint(i) < uint(size()));
  *(reinterpret_cast<uchar*>(d.data())+1+(i>>3)) &= ~uchar(1 << (i & 7)); }
 
 inline void QBitArray::setBit(int i, bool val)
 { if (val) setBit(i); else clearBit(i); }
 
 inline bool QBitArray::toggleBit(int i)
-{ Q_ASSERT(i >= 0 &&  i < size());
+{ Q_ASSERT(uint(i) < uint(size()));
  uchar b = uchar(1<<(i&7)); uchar* p = reinterpret_cast<uchar*>(d.data())+1+(i>>3);
  uchar c = uchar(*p&b); *p^=b; return c!=0; }
 
diff --git a/src/corelib/tools/qbytearray.h b/src/corelib/tools/qbytearray.h
index 7be0739a11..e4455006ad 100644
--- a/src/corelib/tools/qbytearray.h
+++ b/src/corelib/tools/qbytearray.h
@@ -411,9 +411,9 @@ inline const char QByteArray::operator[](uint i) const
 { Q_ASSERT(i < uint(size())); return d->data[i]; }
 #else
 inline char QByteArray::at(int i) const
-{ Q_ASSERT(i >= 0 && i < size()); return d->data[i]; }
+{ Q_ASSERT(uint(i) < uint(size())); return d->data[i]; }
 inline char QByteArray::operator[](int i) const
-{ Q_ASSERT(i >= 0 && i < size()); return d->data[i]; }
+{ Q_ASSERT(uint(i) < uint(size())); return d->data[i]; }
 inline char QByteArray::operator[](uint i) const
 { Q_ASSERT(i < uint(size())); return d->data[i]; }
 #endif
diff --git a/src/corelib/tools/qstring.h b/src/corelib/tools/qstring.h
index 8e34f5c849..46b183a74d 100644
--- a/src/corelib/tools/qstring.h
+++ b/src/corelib/tools/qstring.h
@@ -1172,7 +1172,7 @@ public:
     QStringRef appendTo(QString *string) const;
 
     inline const QChar at(int i) const
-        { Q_ASSERT(i >= 0 && i < size()); return m_string->at(i + m_position); }
+        { Q_ASSERT(uint(i) < uint(size())); return m_string->at(i + m_position); }
 
     int compare(const QString &s, Qt::CaseSensitivity cs = Qt::CaseSensitive) const;
     int compare(const QStringRef &s, Qt::CaseSensitivity cs = Qt::CaseSensitive) const;