3 files changed, 14 insertions, 2 deletions
diff --git a/src/corelib/io/qiodevice.cpp b/src/corelib/io/qiodevice.cpp
index 0709a93bad..72ec6ff403 100644
--- a/src/corelib/io/qiodevice.cpp
+++ b/src/corelib/io/qiodevice.cpp
@@ -1025,7 +1025,7 @@ QByteArray QIODevice::readAll()
     } else {
         // Read it all in one go.
         // If resize fails, don't read anything.
-        if (readBytes + theSize - d->pos > INT_MAX)
+        if (quint64(readBytes + theSize - d->pos) > QByteArray::MaxSize)
             return QByteArray();
         result.resize(int(readBytes + theSize - d->pos));
         readBytes += read(result.data() + readBytes, result.size() - readBytes);
diff --git a/src/corelib/tools/qbytearray.cpp b/src/corelib/tools/qbytearray.cpp
index 6ac442d27b..d8b2efbef3 100644
--- a/src/corelib/tools/qbytearray.cpp
+++ b/src/corelib/tools/qbytearray.cpp
@@ -63,7 +63,7 @@ int qFindByteArray(
 int qAllocMore(int alloc, int extra) Q_DECL_NOTHROW
 {
     Q_ASSERT(alloc >= 0 && extra >= 0);
-    Q_ASSERT_X(alloc < (1 << 30) - extra, "qAllocMore", "Requested size is too large!");
+    Q_ASSERT_X(uint(alloc) < QByteArray::MaxSize, "qAllocMore", "Requested size is too large!");
 
     unsigned nalloc = qNextPowerOfTwo(alloc + extra);
 
@@ -777,6 +777,15 @@ static inline char qToLower(char c)
 */
 
 /*!
+    \variable QByteArray::MaxSize
+    \internal
+    \since 5.4
+
+    The maximum size of a QByteArray, in bytes. Also applies to a the maximum
+    storage size of QString and QVector, though not the number of elements.
+*/
+
+/*!
     \enum QByteArray::Base64Option
     \since 5.2
 
diff --git a/src/corelib/tools/qbytearray.h b/src/corelib/tools/qbytearray.h
index f13b1c16cd..3bcc7b1f2a 100644
--- a/src/corelib/tools/qbytearray.h
+++ b/src/corelib/tools/qbytearray.h
@@ -173,6 +173,9 @@ private:
     typedef QTypedArrayData<char> Data;
 
 public:
+    // undocumented:
+    static const quint64 MaxSize = (1 << 30) - sizeof(Data);
+
     enum Base64Option {
         Base64Encoding = 0,
         Base64UrlEncoding = 1,