warning: pasting would not give a valid preprocessing token

[Neil Booth]

[There's no point cc-ing Zack; his mail address is no more]

Byron,

I hope this fixes it for you.  I'm bootstrapping now, and will then
run the testsuite.

This area is a bit ugly and in bad need of a cleanup.  I need to
extract more flexibility from the lexer first, though.  The problem
was in the way we handle macro arguments: each argument is a list of
pointers to the tokens making up the argument.  These tend to point to
the original tokens (in this case, the comma in the macro definition
in the hash table).  That token has a PASTE_LEFT flag to say it's on
the left hand side of a ##.  The problem is that after processing the
paste, and correctly not emitting a warning about invalid pastes, we
maintained a pointer to the same comma for the nested macro
replacements (since it is part of an argument itself).  Unforunately,
of course, that comma still has its paste flag set, so the paste
mechanism gets re-invoked in later unintended places; hence the
(repeated) warnings.

This is a nice testcase for quite a deep nested macro bug.  I
simplified your case to the one below, which I'll commit along with
the fix.  If you have a chance, please give it a whirl.

It also fixes a bug in ON_REST_ARG - the macro was testing the flags
of the wrong thing (easy to do since #defines are typeless).  Any
relief the original fix brought might therefore be undone; I'd be
interested in knowing if the warnings it "cured" come back with this
patch.

OK to commit?

Neil.

	* cpplex.c (ON_REST_ARG): Correct the test.
	(maybe_paste_with_next): Duplicate a token that fail pasting,
	and clear its PASTE_LEFT flag, so that nested pasting attempts
	do not occur.
	* gcc.dg/cpp/paste10.c: Testcase.

Index: cpplex.c
===================================================================
RCS file: /cvs/gcc/egcs/gcc/cpplex.c,v
retrieving revision 1.95
diff -u -p -r1.95 cpplex.c
--- cpplex.c	2000/09/12 03:42:29	1.95
+++ cpplex.c	2000/09/14 22:28:32
@@ -201,9 +201,9 @@ TOKEN_LEN (token)
 #define IS_ARG_CONTEXT(c) ((c)->flags & CONTEXT_ARG)
 #define CURRENT_CONTEXT(pfile) ((pfile)->contexts + (pfile)->cur_context)
 #define ON_REST_ARG(c) \
- (((c)->flags & VAR_ARGS) \
-  && ((c)-1)->u.list->tokens[((c)-1)->posn - 1].val.aux \
-      == (unsigned int) (((c)-1)->u.list->paramc - 1))
+ (((c)->u.list->flags & VAR_ARGS) \
+  && (c)->u.list->tokens[(c)->posn - 1].val.aux \
+      == (unsigned int) ((c)->u.list->paramc - 1))
 
 #define ASSIGN_FLAGS_AND_POS(d, s) \
   do {(d)->flags = (s)->flags & (PREV_WHITE | BOL | PASTE_LEFT); \
@@ -2787,14 +2787,17 @@ maybe_paste_with_next (pfile, token)
 		     the special extended semantics (see above).  */
 		  if (token->type == CPP_COMMA
 		      && IS_ARG_CONTEXT (CURRENT_CONTEXT (pfile))
-		      && ON_REST_ARG (CURRENT_CONTEXT (pfile)))
+		      && ON_REST_ARG (CURRENT_CONTEXT (pfile) - 1))
 		    /* no warning */;
 		  else
 		    cpp_warning (pfile,
 			"pasting would not give a valid preprocessing token");
 		}
 	      _cpp_push_token (pfile, second);
-	      return token;
+	      /* A short term hack to safely clear the PASTE_LEFT flag.  */
+	      pasted = duplicate_token (pfile, token);
+	      pasted->flags &= ~PASTE_LEFT;
+	      return pasted;
 	    }
 
 	  if (type == CPP_NAME || type == CPP_NUMBER)
Index: cmdlne-C.c
===================================================================
RCS file: /cvs/gcc/egcs/gcc/testsuite/gcc.dg/cpp/cmdlne-C.c,v
retrieving revision 1.2
diff -u -p -r1.2 cmdlne-C.c
--- cmdlne-C.c	2000/07/11 13:51:39	1.2
+++ cmdlne-C.c	2000/09/14 22:47:29
@@ -10,7 +10,7 @@
    the beginning of a directive turns it into a non-directive.  */
 
 #define simple no comments
-#/**/define bad_directive		/* { dg-error "invalid" } */
+
 #define/**/obj_like/**/(some)/**/thing/**/
 #define fun_like(/**/x/**/,/**/y/**/)/**/
 /**/#define not_a_macro
Index: paste10.c
===================================================================
RCS file: paste10.c
diff -N paste10.c
--- /dev/null	Tue May  5 13:32:27 1998
+++ paste10.c	Thu Sep 14 15:47:29 2000
@@ -0,0 +1,14 @@
+/* Copyright (C) 2000 Free Software Foundation, Inc.  */
+
+/* { dg-do preprocess } */
+
+/* This testcase used to produce a bogus "invalid paste" warning, owing
+   to not clearing a PASTE_LEFT flag.  */
+
+#define strcpy(src) __strcpy_small (src)
+
+#define __strcpy_small(src) src
+
+#define tprintf(format, args...) sprintf(format, ## args)
+
+strcpy(tprintf("<%s>", test))