README: Document some known limitations.

None of these are fundamental---just a few things that haven't been
implemented yet.

diff --git a/README b/README
index ba833a49ffbd04a4d051f39f0ba01254693eb8c9..f0f64c2644a9c572d3234383033c64dfccad219b 100644 (file)
--- a/README
+++ b/README
@@ -12,3 +12,15 @@ preprocessors". To fill in these details, I've been using the C99
 standard (for which I had a convenient copy) as available from:
 
 http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1124.pdf
+
+Known limitations
+-----------------
+Macro invocations cannot include embedded newlines.
+
+The __LINE__, __FILE__, and __VERSION__ macros are not yet supported.
+
+The argument of the 'defined' operator cannot yet include enclosing
+parentheses.
+
+The #error, #pragma, #extension, #version, and #line macros are not
+yet supported.