PEP 7: Add C pre-processor macro style recommendations

peps/pep-0007.rst

@@ -135,6 +135,20 @@ Code lay-out
           return 0; /* "Forgive" adding a __dict__ only */
       }
 
+* Vertically align line continuation characters in multi-line macros.
+
+* Macros intended to be used as a statement should use the
+  ``do {... }while(0)``` macro idiom.
+  Example::
+
+      #define ADD_INT_MACRO(MOD, INT) do {                          \
+          if (PyModule_AddIntConstant((MOD), (#INT), (INT)) < 0) {  \
+              goto error;                                           \
+          }                                                         \
+      } while (0)
+
+* ``#undef`` macros after use.
+
 * Put blank lines around functions, structure definitions, and major
   sections inside functions.
 
@@ -170,6 +184,9 @@ Naming conventions
 * Macros should have a MixedCase prefix and then use upper case, for
   example: ``PyString_AS_STRING``, ``Py_PRINT_RAW``.
 
+* Macro parameters should use ``ALL_CAPS`` style,
+  so they are easily distinguishable from C variables and struct members.
+
 
 Documentation Strings
 =====================