preprocessor: Deferred macro support

For deferred macros we also need a new field on the macro itself, so
that the module machinery can determine the macro was imported.  Also
the documentation for the hashnode's deferred field was incomplete.

	libcpp/
	* include/cpplib.h (struct cpp_macro): Add imported_p field.
	(struct cpp_hashnode): Tweak deferred field documentation.
	* macro.c (_cpp_new_macro): Clear new field.
	(cpp_get_deferred_macro, get_deferred_or_lazy_macro): Assert
	more.

1 files changed, 8 insertions, 3 deletions

diff --git a/libcpp/include/cpplib.h b/libcpp/include/cpplib.h
index 692aee5..50d28dc 100644
--- a/libcpp/include/cpplib.h
+++ b/libcpp/include/cpplib.h
@@ -826,7 +826,10 @@ struct GTY(()) cpp_macro {
      tokens.  */
   unsigned int extra_tokens : 1;
 
-  /* 1 bits spare (32-bit). 33 on 64-bit target.  */
+  /* Imported C++20 macro (from a header unit).  */
+  unsigned int imported_p : 1;
+
+  /* 0 bits spare (32-bit). 32 on 64-bit target.  */
 
   union cpp_exp_u
   {
@@ -921,9 +924,11 @@ struct GTY(()) cpp_hashnode {
 
   /* 5 bits spare.  */
 
-  /* On a 64-bit system there would be 32-bits of padding to the value
+  /* The deferred cookie is applicable to NT_USER_MACRO or NT_VOID.
+     The latter for when a macro had a prevailing undef.
+     On a 64-bit system there would be 32-bits of padding to the value
      field.  So placing the deferred index here is not costly.   */
-  unsigned deferred;			/* Deferred index, (unless zero).  */
+  unsigned deferred;			/* Deferred cookie  */
 
   union _cpp_hashnode_value GTY ((desc ("%1.type"))) value;
 };