C++, handle (escaped) line breaks in epxr role

Fixes sphinx-doc/sphinx#4825

CHANGES

@@ -22,7 +22,9 @@ Bugs fixed
 * #4863, #4938, #4939: i18n doesn't handle node.title correctly tat used for
   contents, topic, admonition, table and section.
 * #4913: i18n: literal blocks in bullet list are not translated
-* #4962: cpp domain: raises TypeError on duplicate declaration
+* #4962: C++, raised TypeError on duplicate declaration.
+* #4825: C++, properly parse expr roles and give better error messages when
+  (escaped) line breaks are present.
 
 Testing
 --------

sphinx/domains/cpp.py

@@ -12,7 +12,7 @@
 import re
 from copy import deepcopy
 
-from docutils import nodes
+from docutils import nodes, utils
 from docutils.parsers.rst import Directive, directives
 from six import iteritems, text_type
 
@@ -5962,7 +5962,7 @@ class CPPExprRole(object):
         class Warner(object):
             def warn(self, msg):
                 inliner.reporter.warning(msg, line=lineno)
-
+        text = utils.unescape(text).replace('\n', ' ')
         env = inliner.document.settings.env
         parser = DefinitionParser(text, Warner(), env.config)
         try: