1 files changed, 44 insertions, 0 deletions
diff --git a/Help/policy/CMP0053.rst b/Help/policy/CMP0053.rst
new file mode 100644
index 0000000..fac430e
--- /dev/null
+++ b/Help/policy/CMP0053.rst
@@ -0,0 +1,44 @@
+CMP0053
+-------
+
+Simplify variable reference and escape sequence evaluation.
+
+CMake 3.1 introduced a much faster implementation of evaluation of the
+:ref:`Variable References` and :ref:`Escape Sequences` documented in the
+:manual:`cmake-language(7)` manual.  While the behavior is identical
+to the legacy implementation in most cases, some corner cases were
+cleaned up to simplify the behavior.  Specifically:
+
+* Expansion of ``@VAR@`` reference syntax defined by the
+  :command:`configure_file` and :command:`string(CONFIGURE)`
+  commands is no longer performed in other contexts.
+
+* Literal ``${VAR}`` reference syntax may contain only
+  alphanumeric characters (``A-Z``, ``a-z``, ``0-9``) and
+  the characters ``_``, ``.``, ``/``, ``-``, and ``+``.
+  Variables with other characters in their name may still
+  be referenced indirectly, e.g.
+
+  .. code-block:: cmake
+
+    set(varname "otherwise & disallowed $ characters")
+    message("${${varname}}")
+
+* The setting of policy :policy:`CMP0010` is not considered,
+  so improper variable reference syntax is always an error.
+
+* More characters are allowed to be escaped in variable names.
+  Previously, only ``()#" \#@^`` were valid characters to
+  escape. Now any non-alphanumeric, non-semicolon, non-NUL
+  character may be escaped following the ``escape_identity``
+  production in the :ref:`Escape Sequences` section of the
+  :manual:`cmake-language(7)` manual.
+
+The ``OLD`` behavior for this policy is to honor the legacy behavior for
+variable references and escape sequences.  The ``NEW`` behavior is to
+use the simpler variable expansion and escape sequence evaluation rules.
+
+This policy was introduced in CMake version 3.1.
+CMake version |release| warns when the policy is not set and uses
+``OLD`` behavior.  Use the :command:`cmake_policy` command to set
+it to ``OLD`` or ``NEW`` explicitly.