Breaking-Features-in-Version-6.md

@@ -7,4 +7,21 @@ Multiple `estimated_params` blocks now concatenate their contents, instead of ov
 ```
 estimated_params(overwrite);
 end; 
-```
+```
\ No newline at end of file
+
+# Changes related to the macro-processor
+
+A macro-processor variable defined without a value will now be equal to `true` (it would previously be equal to `1`).
+
+This affects lines such as:
+```
+@#define var
+```
+in a `.mod` file.
+
+This also affects variable defined on the `dynare` command line, such as:
+```
+dynare myfile.mod -Dvar
+```
+
+This should normally have no impact, since variable thus defined are typically tested with `@#ifdef`/`@#ifndef` (in which case their value does not matter).