[rtems-docs commit] user: Add v5 to v6 migration help

[Sebastian Huber]

Module:    rtems-docs
Branch:    master
Commit:    b6a1d396b6984f5d11dfdcaf8efba5a7fa405ed2
Changeset: http://git.rtems.org/rtems-docs/commit/?id=b6a1d396b6984f5d11dfdcaf8efba5a7fa405ed2

Author:    Sebastian Huber <sebastian.huber at embedded-brains.de>
Date:      Tue Jul  7 15:05:21 2020 +0200

user: Add v5 to v6 migration help

---

 user/migration/index.rst    |  1 +
 user/migration/v5-to-v6.rst | 20 ++++++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/user/migration/index.rst b/user/migration/index.rst
index 76012b5..06af484 100644
--- a/user/migration/index.rst
+++ b/user/migration/index.rst
@@ -15,3 +15,4 @@ from one version of RTEMS to a new version.
 .. toctree::
 
     v4_11-to-v5
+    v5-to-v6
diff --git a/user/migration/v5-to-v6.rst b/user/migration/v5-to-v6.rst
new file mode 100644
index 0000000..5997057
--- /dev/null
+++ b/user/migration/v5-to-v6.rst
@@ -0,0 +1,20 @@
+.. SPDX-License-Identifier: CC-BY-SA-4.0
+
+.. Copyright (C) 2020 embedded brains GmbH (http://www.embedded-brains.de)
+
+.. _Migration_5_to_6:
+
+RTEMS 5 to RTEMS 6
+==================
+
+This section provides helpful information when migrating from RTEMS 5 to
+RTEMS 6.
+
+Update to GCC 10
+----------------
+
+The tool suite for RTEMS 6 uses GCC 10.  GCC 10 enables ``-fno-common`` by
+default.  Code bases which never used this option before may observe now
+multiple definition linker errors.  For example, if global variables are
+declared and defined in header files (usually a missing ``extern`` in the header
+file).