Explicit error for comments, with README link

Author: cellularmitosis

README.rst

@@ -110,9 +110,9 @@ Interaction with the C preprocessor
 -----------------------------------
 
 In order to be compilable, C code must be preprocessed by the C preprocessor -
-``cpp``. ``cpp`` handles preprocessing directives like ``#include`` and
+``cpp``. A compatible ``cpp`` handles preprocessing directives like ``#include`` and
 ``#define``, removes comments, and performs other minor tasks that prepare the C
-code for compilation.
+code for compilation. Note that clang's cpp does not remove comments.
 
 For all but the most trivial snippets of C code **pycparser**, like a C
 compiler, must receive preprocessed C code in order to function correctly. If

pycparser/c_lexer.py

@@ -209,6 +209,10 @@ def _make_tok_location(self, token):
 
     bad_octal_constant = '0[0-7]*[89]'
 
+    # comments are not supported
+    unsupported_c_style_comment = r'\/\*'
+    unsupported_cxx_style_comment = r'\/\/'
+
     # character constants (K&R2: A.2.5.2)
     # Note: a-zA-Z and '.-~^_!=&;,' are allowed as escape chars to support #line
     # directives with Windows paths as filenames (..\..\dir\file)
@@ -475,6 +479,16 @@ def t_BAD_CONST_OCT(self, t):
         msg = "Invalid octal constant"
         self._error(msg, t)
 
+    @TOKEN(unsupported_c_style_comment)
+    def t_UNSUPPORTED_C_STYLE_COMMENT(self, t):
+        msg = "Comments are not supported, see https://github.com/eliben/pycparser#3using."
+        self._error(msg, t)
+
+    @TOKEN(unsupported_cxx_style_comment)
+    def t_UNSUPPORTED_CXX_STYLE_COMMENT(self, t):
+        msg = "Comments are not supported, see https://github.com/eliben/pycparser#3using."
+        self._error(msg, t)
+
     @TOKEN(octal_constant)
     def t_INT_CONST_OCT(self, t):
         return t