Document OOM conditions in the QArrayData-based containers

The other containers probably don't handle as well, so I just documented
the ones that I know how they work.

Fixes: QTBUG-75470
Change-Id: I95ecabe2f50e450c991afffd159a0483aac35a79
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>
Reviewed-by: Albert Astals Cid <aacid@kde.org>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/src/corelib/tools/qstring.cpp b/src/corelib/tools/qstring.cpp
index ee9d486eb8..a0e33d4e45 100644
--- a/src/corelib/tools/qstring.cpp
+++ b/src/corelib/tools/qstring.cpp
@@ -1777,6 +1777,24 @@ const QString::Null QString::null = { };
     and the \c{'+'} will automatically be performed as the
     \c{QStringBuilder} \c{'%'} everywhere.
 
+    \section1 Maximum size and out-of-memory conditions
+
+    The current version of QString is limited to just under 2 GB (2^31 bytes)
+    in size. The exact value is architecture-dependent, since it depends on the
+    overhead required for managing the data block, but is no more than 32
+    bytes. Raw data blocks are also limited by the use of \c int type in the
+    current version to 2 GB minus 1 byte. Since QString uses two bytes per
+    character, that translates to just under 2^30 characters in one QString.
+
+    In case memory allocation fails, QString will throw a \c std::bad_alloc
+    exception. Out of memory conditions in the Qt containers are the only case
+    where Qt will throw exceptions.
+
+    Note that the operating system may impose further limits on applications
+    holding a lot of allocated memory, especially large, contiguous blocks.
+    Such considerations, the configuration of such behavior or any mitigation
+    are outside the scope of the Qt API.
+
     \sa fromRawData(), QChar, QLatin1String, QByteArray, QStringRef
 */