preprocessor: Add deferred macros

Deferred macros are needed for C++ modules.  Header units may export
macro definitions and undefinitions.  These are resolved lazily at the
point of (potential) use.  (The language specifies that, it's not just
a useful optimization.)  Thus, identifier nodes grow a 'deferred'
field, which fortunately doesn't expand the structure on 64-bit
systems as there was padding there.  This is non-zero on NT_MACRO
nodes, if the macro is deferred.  When such an identifier is lexed, it
is resolved via a callback that I added recently.  That will either
provide the macro definition, or discover it there was an overriding
undef.  Either way the identifier is no longer a deferred macro.
Notice it is now possible for NT_MACRO nodes to have a NULL macro
expansion.

	libcpp/
	* include/cpplib.h (struct cpp_hashnode): Add deferred field.
	(cpp_set_deferred_macro): Define.
	(cpp_get_deferred_macro): Declare.
	(cpp_macro_definition): Reformat, add overload.
	(cpp_macro_definition_location): Deal with deferred macro.
	(cpp_alloc_token_string, cpp_compare_macro): Declare.
	* internal.h (_cpp_notify_macro_use): Return bool
	(_cpp_maybe_notify_macro_use): Likewise.
	* directives.c (do_undef): Check macro is not undef before
	warning.
	(do_ifdef, do_ifndef): Deal with deferred macro.
	* expr.c (parse_defined): Likewise.
	* lex.c (cpp_allocate_token_string): Break out of ...
	(create_literal): ... here.  Call it.
	(cpp_maybe_module_directive): Deal with deferred macro.
	* macro.c (cpp_get_token_1): Deal with deferred macro.
	(warn_of_redefinition): Deal with deferred macro.
	(compare_macros): Rename to ...
	(cpp_compare_macro): ... here.  Make extern.
	(cpp_get_deferred_macro): New.
	(_cpp_notify_macro_use): Deal with deferred macro, return bool
	indicating definedness.
	(cpp_macro_definition): Deal with deferred macro.

1 files changed, 6 insertions, 3 deletions

diff --git a/libcpp/expr.c b/libcpp/expr.c
index b98c038..2ba7726 100644
--- a/libcpp/expr.c
+++ b/libcpp/expr.c
@@ -1068,6 +1068,7 @@ parse_defined (cpp_reader *pfile)
 	}
     }
 
+  bool is_defined = false;
   if (node)
     {
       if ((pfile->context != initial_context
@@ -1075,9 +1076,11 @@ parse_defined (cpp_reader *pfile)
 	  && CPP_OPTION (pfile, warn_expansion_to_defined))
         cpp_pedwarning (pfile, CPP_W_EXPANSION_TO_DEFINED,
 		        "this use of \"defined\" may not be portable");
-
+      is_defined = _cpp_defined_macro_p (node);
+      if (!_cpp_maybe_notify_macro_use (pfile, node, token->src_loc))
+	/* It wasn't a macro after all.  */
+	is_defined = false;
       _cpp_mark_macro_used (node);
-      _cpp_maybe_notify_macro_use (pfile, node, token->src_loc);
 
       /* A possible controlling macro of the form #if !defined ().
 	 _cpp_parse_expr checks there was no other junk on the line.  */
@@ -1093,7 +1096,7 @@ parse_defined (cpp_reader *pfile)
   result.unsignedp = false;
   result.high = 0;
   result.overflow = false;
-  result.low = node && _cpp_defined_macro_p (node);
+  result.low = is_defined;
   return result;
 }