cppopts.texi (-dU): Document.

gcc:
	* doc/cppopts.texi (-dU): Document.
	* c-common.h (flag_dump_macros): Update comment.
	* c-opts.c (handle_OPT_d): Handle -dU.
	* c-ppoutput.c (macro_queue, define_queue, undef_queue,
	dump_queued_macros, cb_used_define, cb_used_undef): New.
	(init_pp_output): Handle -dU.
	(cb_line_change): Call dump_queued_macros.
	* toplev.c (decode_d_option): Accept -dU as preprocessor option.

gcc/testsuite:
	* gcc.dg/cpp/cmdlne-dU-1.c, gcc.dg/cpp/cmdlne-dU-2.c,
	gcc.dg/cpp/cmdlne-dU-3.c, gcc.dg/cpp/cmdlne-dU-4.c,
	gcc.dg/cpp/cmdlne-dU-5.c, gcc.dg/cpp/cmdlne-dU-6.c,
	gcc.dg/cpp/cmdlne-dU-7.c, gcc.dg/cpp/cmdlne-dU-8.c,
	gcc.dg/cpp/cmdlne-dU-9.c, gcc.dg/cpp/cmdlne-dU-10.c,
	gcc.dg/cpp/cmdlne-dU-11.c, gcc.dg/cpp/cmdlne-dU-12.c,
	gcc.dg/cpp/cmdlne-dU-13.c, gcc.dg/cpp/cmdlne-dU-14.c,
	gcc.dg/cpp/cmdlne-dU-15.c, gcc.dg/cpp/cmdlne-dU-16.c,
	gcc.dg/cpp/cmdlne-dU-17.c, gcc.dg/cpp/cmdlne-dU-18.c,
	gcc.dg/cpp/cmdlne-dU-19.c, gcc.dg/cpp/cmdlne-dU-20.c,
	gcc.dg/cpp/cmdlne-dU-21.c, gcc.dg/cpp/cmdlne-dU-22.c: New tests.

libcpp:
	* include/cpplib.h (struct cpp_callbacks): Add used_define,
	used_undef and before_define.
	(NODE_USED): Define.
	* directives.c (do_define, do_undef, undefine_macros, do_ifdef,
	do_ifndef, cpp_pop_definition): Handle new flag and use new
	callbacks.
	* expr.c (parse_defined): Handle new flag and use new callbacks.
	* macro.c (enter_macro_context, _cpp_free_definition): Handle new
	flag and use new callbacks.

From-SVN: r133847

gcc/ChangeLog

@@ -1,3 +1,14 @@
+2008-04-02  Joseph Myers  <joseph@codesourcery.com>
+
+	* doc/cppopts.texi (-dU): Document.
+	* c-common.h (flag_dump_macros): Update comment.
+	* c-opts.c (handle_OPT_d): Handle -dU.
+	* c-ppoutput.c (macro_queue, define_queue, undef_queue,
+	dump_queued_macros, cb_used_define, cb_used_undef): New.
+	(init_pp_output): Handle -dU.
+	(cb_line_change): Call dump_queued_macros.
+	* toplev.c (decode_d_option): Accept -dU as preprocessor option.
+
 2008-04-02  Anatoly Sokolov <aesok@post.ru>
 
 	* config/avr/predicates.md (io_address_operand): New predicate. 

gcc/c-common.h

@@ -358,8 +358,8 @@ extern char flag_no_line_commands;
 
 extern char flag_no_output;
 
-/* Nonzero means dump macros in some fashion; contains the 'D', 'M' or
+/* Nonzero means dump macros in some fashion; contains the 'D', 'M',
-   'N' of the command line switch.  */
+   'N' or 'U' of the command line switch.  */
 
 extern char flag_dump_macros;
 

gcc/c-opts.c

@@ -1668,6 +1668,7 @@ handle_OPT_d (const char *arg)
       case 'M':			/* Dump macros only.  */
       case 'N':			/* Dump names.  */
       case 'D':			/* Dump definitions.  */
+      case 'U':			/* Dump used macros.  */
 	flag_dump_macros = c;
 	break;
 

gcc/c-ppoutput.c

@@ -39,6 +39,17 @@ static struct
   bool first_time;		/* pp_file_change hasn't been called yet.  */
 } print;
 
+/* Defined and undefined macros being queued for output with -dU at
+   the next newline.  */
+typedef struct macro_queue
+{
+  struct macro_queue *next;	/* Next macro in the list.  */
+  char *macro;			/* The name of the macro if not
+				   defined, the full definition if
+				   defined.  */
+} macro_queue;
+static macro_queue *define_queue, *undef_queue;
+
 /* General output routines.  */
 static void scan_translation_unit (cpp_reader *);
 static void print_lines_directives_only (int, const void *, size_t);
@@ -46,6 +57,7 @@ static void scan_translation_unit_directives_only (cpp_reader *);
 static void scan_translation_unit_trad (cpp_reader *);
 static void account_for_newlines (const unsigned char *, size_t);
 static int dump_macro (cpp_reader *, cpp_hashnode *, void *);
+static void dump_queued_macros (cpp_reader *);
 
 static void print_line (source_location, const char *);
 static void maybe_print_line (source_location);
@@ -55,6 +67,8 @@ static void maybe_print_line (source_location);
 static void cb_line_change (cpp_reader *, const cpp_token *, int);
 static void cb_define (cpp_reader *, source_location, cpp_hashnode *);
 static void cb_undef (cpp_reader *, source_location, cpp_hashnode *);
+static void cb_used_define (cpp_reader *, source_location, cpp_hashnode *);
+static void cb_used_undef (cpp_reader *, source_location, cpp_hashnode *);
 static void cb_include (cpp_reader *, source_location, const unsigned char *,
 			const char *, int, const cpp_token **);
 static void cb_ident (cpp_reader *, source_location, const cpp_string *);
@@ -125,6 +139,13 @@ init_pp_output (FILE *out_stream)
       cb->undef  = cb_undef;
     }
 
+  if (flag_dump_macros == 'U')
+    {
+      cb->before_define = dump_queued_macros;
+      cb->used_define = cb_used_define;
+      cb->used_undef = cb_used_undef;
+    }
+
   /* Initialize the print structure.  Setting print.src_line to -1 here is
      a trick to guarantee that the first token of the file will cause
      a linemarker to be output by maybe_print_line.  */
@@ -320,6 +341,9 @@ cb_line_change (cpp_reader *pfile, const cpp_token *token,
 {
   source_location src_loc = token->src_loc;
 
+  if (define_queue || undef_queue)
+    dump_queued_macros (pfile);
+
   if (token->type == CPP_EOF || parsing_args)
     return;
 
@@ -379,6 +403,68 @@ cb_undef (cpp_reader *pfile ATTRIBUTE_UNUSED, source_location line,
   print.src_line++;
 }
 
+static void
+cb_used_define (cpp_reader *pfile, source_location line ATTRIBUTE_UNUSED,
+		cpp_hashnode *node)
+{
+  macro_queue *q;
+  q = XNEW (macro_queue);
+  q->macro = xstrdup ((const char *) cpp_macro_definition (pfile, node));
+  q->next = define_queue;
+  define_queue = q;
+}
+
+static void
+cb_used_undef (cpp_reader *pfile ATTRIBUTE_UNUSED,
+	       source_location line ATTRIBUTE_UNUSED,
+	       cpp_hashnode *node)
+{
+  macro_queue *q;
+  q = XNEW (macro_queue);
+  q->macro = xstrdup ((const char *) NODE_NAME (node));
+  q->next = undef_queue;
+  undef_queue = q;
+}
+
+static void
+dump_queued_macros (cpp_reader *pfile ATTRIBUTE_UNUSED)
+{
+  macro_queue *q;
+
+  /* End the previous line of text.  */
+  if (print.printed)
+    {
+      putc ('\n', print.outf);
+      print.src_line++;
+      print.printed = 0;
+    }
+
+  for (q = define_queue; q;)
+    {
+      macro_queue *oq;
+      fputs ("#define ", print.outf);
+      fputs (q->macro, print.outf);
+      putc ('\n', print.outf);
+      print.src_line++;
+      oq = q;
+      q = q->next;
+      free (oq->macro);
+      free (oq);
+    }
+  define_queue = NULL;
+  for (q = undef_queue; q;)
+    {
+      macro_queue *oq;
+      fprintf (print.outf, "#undef %s\n", q->macro);
+      print.src_line++;
+      oq = q;
+      q = q->next;
+      free (oq->macro);
+      free (oq);
+    }
+  undef_queue = NULL;
+}
+
 static void
 cb_include (cpp_reader *pfile ATTRIBUTE_UNUSED, source_location line,
 	    const unsigned char *dir, const char *header, int angle_brackets,

gcc/doc/cppopts.texi

@@ -682,6 +682,14 @@ Like @samp{D}, but emit only the macro names, not their expansions.
 @opindex dI
 Output @samp{#include} directives in addition to the result of
 preprocessing.
+
+@item U
+@opindex dU
+Like @samp{D} except that only macros that are expanded, or whose
+definedness is tested in preprocessor directives, are output; the
+output is delayed until the use or test of the macro; and
+@samp{#undef} directives are also output for macros tested but
+undefined at the time.
 @end table
 
 @item -P

gcc/testsuite/ChangeLog

@@ -1,3 +1,17 @@
+2008-04-02  Joseph Myers  <joseph@codesourcery.com>
+
+	* gcc.dg/cpp/cmdlne-dU-1.c, gcc.dg/cpp/cmdlne-dU-2.c,
+	gcc.dg/cpp/cmdlne-dU-3.c, gcc.dg/cpp/cmdlne-dU-4.c,
+	gcc.dg/cpp/cmdlne-dU-5.c, gcc.dg/cpp/cmdlne-dU-6.c,
+	gcc.dg/cpp/cmdlne-dU-7.c, gcc.dg/cpp/cmdlne-dU-8.c,
+	gcc.dg/cpp/cmdlne-dU-9.c, gcc.dg/cpp/cmdlne-dU-10.c,
+	gcc.dg/cpp/cmdlne-dU-11.c, gcc.dg/cpp/cmdlne-dU-12.c,
+	gcc.dg/cpp/cmdlne-dU-13.c, gcc.dg/cpp/cmdlne-dU-14.c,
+	gcc.dg/cpp/cmdlne-dU-15.c, gcc.dg/cpp/cmdlne-dU-16.c,
+	gcc.dg/cpp/cmdlne-dU-17.c, gcc.dg/cpp/cmdlne-dU-18.c,
+	gcc.dg/cpp/cmdlne-dU-19.c, gcc.dg/cpp/cmdlne-dU-20.c,
+	gcc.dg/cpp/cmdlne-dU-21.c, gcc.dg/cpp/cmdlne-dU-22.c: New tests.
+
 2008-04-02  Richard Guenther  <rguenther@suse.de>
 
 	PR tree-optimization/14495

gcc/testsuite/gcc.dg/cpp/cmdlne-dU-1.c

@@ -0,0 +1,5 @@
+/* { dg-do preprocess } */
+/* { dg-options "-P -dU" } */
+/* { dg-final { scan-file cmdlne-dU-1.i "^\n*#undef A\n*$" } } */
+#ifdef A
+#endif

gcc/testsuite/gcc.dg/cpp/cmdlne-dU-10.c

@@ -0,0 +1,7 @@
+/* { dg-do preprocess } */
+/* { dg-options "-P -dU" } */
+/* { dg-final { scan-file cmdlne-dU-10.i "^\n*C\n+#define B C\n+#define A B\n*$" } } */
+/* This file deliberately has no final newline.  */
+#define A B
+#define B C
+A

gcc/testsuite/gcc.dg/cpp/cmdlne-dU-11.c

@@ -0,0 +1,7 @@
+/* { dg-do preprocess } */
+/* { dg-options "-P -dU" } */
+/* { dg-final { scan-file cmdlne-dU-11.i "^\n*\n*$" } } */
+#define A B
+#if 0
+A
+#endif

gcc/testsuite/gcc.dg/cpp/cmdlne-dU-12.c

@@ -0,0 +1,6 @@
+/* { dg-do preprocess } */
+/* { dg-options "-P -dU" } */
+/* { dg-final { scan-file cmdlne-dU-12.i "^\n*#define A 1\n*$" } } */
+#define A 1
+#if A
+#endif

gcc/testsuite/gcc.dg/cpp/cmdlne-dU-13.c

@@ -0,0 +1,7 @@
+/* { dg-do preprocess } */
+/* { dg-options "-P -dU" } */
+/* { dg-final { scan-file cmdlne-dU-13.i "^\n*#undef A\n*$" } } */
+#ifdef A
+#endif
+#ifdef A
+#endif

gcc/testsuite/gcc.dg/cpp/cmdlne-dU-14.c

@@ -0,0 +1,6 @@
+/* { dg-do preprocess } */
+/* { dg-options "-P -dU" } */
+/* { dg-final { scan-file cmdlne-dU-14.i "^\n*B\n+#define A B\n+B\n*$" } } */
+#define A B
+A
+A

gcc/testsuite/gcc.dg/cpp/cmdlne-dU-15.c

@@ -0,0 +1,5 @@
+/* { dg-do preprocess } */
+/* { dg-options "-P -dU" } */
+/* { dg-final { scan-file cmdlne-dU-15.i "^\n*\n*$" } } */
+#if A
+#endif

gcc/testsuite/gcc.dg/cpp/cmdlne-dU-16.c

@@ -0,0 +1,5 @@
+/* { dg-do preprocess } */
+/* { dg-options "-P -dU" } */
+/* { dg-final { scan-file cmdlne-dU-16.i "^\n*#define __STDC__ 1\n*$" } } */
+#ifdef __STDC__
+#endif

gcc/testsuite/gcc.dg/cpp/cmdlne-dU-17.c

@@ -0,0 +1,4 @@
+/* { dg-do preprocess } */
+/* { dg-options "-P -dU" } */
+/* { dg-final { scan-file cmdlne-dU-17.i "^\n*1\n+#define __STDC__ 1\n*$" } } */
+__STDC__

gcc/testsuite/gcc.dg/cpp/cmdlne-dU-18.c

@@ -0,0 +1,5 @@
+/* { dg-do preprocess } */
+/* { dg-options "-P -dU" } */
+/* { dg-final { scan-file cmdlne-dU-18.i "^\n*x 1 y\n+#define A 1\n*$" } } */
+#define A 1
+x A y

gcc/testsuite/gcc.dg/cpp/cmdlne-dU-19.c

@@ -0,0 +1,8 @@
+/* { dg-do preprocess } */
+/* { dg-options "-P -dU" } */
+/* { dg-final { scan-file cmdlne-dU-19.i "^\n*B\n+#define A B\n+#undef A\n*$" } } */
+#define A B
+A
+#undef A
+#ifdef A
+#endif

gcc/testsuite/gcc.dg/cpp/cmdlne-dU-2.c

@@ -0,0 +1,6 @@
+/* { dg-do preprocess } */
+/* { dg-options "-P -dU" } */
+/* { dg-final { scan-file cmdlne-dU-2.i "^\n*#define A *\n*$" } } */
+#define A
+#ifdef A
+#endif

gcc/testsuite/gcc.dg/cpp/cmdlne-dU-20.c

@@ -0,0 +1,5 @@
+/* { dg-do preprocess } */
+/* { dg-options "-P -dU" } */
+/* { dg-final { scan-file cmdlne-dU-20.i "^\n*A B\n*$" } } */
+#define A(x) x
+A B

gcc/testsuite/gcc.dg/cpp/cmdlne-dU-21.c

@@ -0,0 +1,9 @@
+/* { dg-do preprocess } */
+/* { dg-options "-P -dU" } */
+/* { dg-final { scan-file cmdlne-dU-21.i "^\n*hello There\n+#define ASTRING There\n+#define MACROARGS\\(A\\) A\n+#undef BSTRING\n*$" } } */
+#define ASTRING There
+#define MACROARGS(A) A
+MACROARGS(hello) ASTRING
+#ifdef BSTRING
+bye
+#endif

gcc/testsuite/gcc.dg/cpp/cmdlne-dU-22.c

@@ -0,0 +1,14 @@
+/* { dg-do preprocess } */
+/* { dg-options "-P -dU" } */
+/* { dg-final { scan-file cmdlne-dU-22.i "^\n*#undef AAA\n+AAA is undefined\n+#undef BBB\n+BBB is undefined\n+#undef CCC\n+CCC is undefined\n*$" } } */
+#ifndef AAA
+AAA is undefined
+#endif
+
+#ifndef BBB
+BBB is undefined
+#endif
+
+#ifndef CCC
+CCC is undefined
+#endif

gcc/testsuite/gcc.dg/cpp/cmdlne-dU-3.c

@@ -0,0 +1,6 @@
+/* { dg-do preprocess } */
+/* { dg-options "-P -dU" } */
+/* { dg-final { scan-file cmdlne-dU-3.i "^\n*#define A B\n*$" } } */
+#define A B
+#ifndef A
+#endif

gcc/testsuite/gcc.dg/cpp/cmdlne-dU-4.c

@@ -0,0 +1,5 @@
+/* { dg-do preprocess } */
+/* { dg-options "-P -dU" } */
+/* { dg-final { scan-file cmdlne-dU-4.i "^\n*#undef A\n*$" } } */
+#if defined(A)
+#endif

gcc/testsuite/gcc.dg/cpp/cmdlne-dU-5.c

@@ -0,0 +1,7 @@
+/* { dg-do preprocess } */
+/* { dg-options "-P -dU" } */
+/* { dg-final { scan-file cmdlne-dU-5.i "^\n*#undef A\n*$" } } */
+#ifdef A
+#ifdef B
+#endif
+#endif

gcc/testsuite/gcc.dg/cpp/cmdlne-dU-6.c

@@ -0,0 +1,8 @@
+/* { dg-do preprocess } */
+/* { dg-options "-P -dU" } */
+/* { dg-final { scan-file cmdlne-dU-6.i "^\n*#undef A\n+#define A *\n*$" } } */
+#ifdef A
+#endif
+#define A
+#ifdef A
+#endif

gcc/testsuite/gcc.dg/cpp/cmdlne-dU-7.c

@@ -0,0 +1,8 @@
+/* { dg-do preprocess } */
+/* { dg-options "-P -dU" } */
+/* { dg-final { scan-file cmdlne-dU-7.i "^\n*B\n+#define A B\n+C\n+#define A C\n*$" } } */
+#define A B
+A
+#undef A
+#define A C
+A

gcc/testsuite/gcc.dg/cpp/cmdlne-dU-8.c

@@ -0,0 +1,6 @@
+/* { dg-do preprocess } */
+/* { dg-options "-P -dU" } */
+/* { dg-final { scan-file cmdlne-dU-8.i "^\n*B D\n+#define A\\(x\\) B x\n+#define C D\n*$" } } */
+#define A(x) B x
+#define C D
+A(C)

gcc/testsuite/gcc.dg/cpp/cmdlne-dU-9.c

@@ -0,0 +1,6 @@
+/* { dg-do preprocess } */
+/* { dg-options "-P -dU" } */
+/* { dg-final { scan-file cmdlne-dU-9.i "^\n*C\n+#define B C\n+#define A B\n*$" } } */
+#define A B
+#define B C
+A

gcc/toplev.c

@@ -1067,6 +1067,7 @@ decode_d_option (const char *arg)
       case 'I':
       case 'M':
       case 'N':
+      case 'U':
 	break;
       case 'H':
 	setup_core_dumping();

libcpp/ChangeLog

@@ -1,3 +1,15 @@
+2008-04-02  Joseph Myers  <joseph@codesourcery.com>
+
+	* include/cpplib.h (struct cpp_callbacks): Add used_define,
+	used_undef and before_define.
+	(NODE_USED): Define.
+	* directives.c (do_define, do_undef, undefine_macros, do_ifdef,
+	do_ifndef, cpp_pop_definition): Handle new flag and use new
+	callbacks.
+	* expr.c (parse_defined): Handle new flag and use new callbacks.
+	* macro.c (enter_macro_context, _cpp_free_definition): Handle new
+	flag and use new callbacks.
+
 2008-04-01  Jakub Jelinek  <jakub@redhat.com>
 
 	PR pch/13675

libcpp/directives.c

@@ -559,9 +559,14 @@ do_define (cpp_reader *pfile)
       pfile->state.save_comments =
 	! CPP_OPTION (pfile, discard_comments_in_macro_exp);
 
+      if (pfile->cb.before_define)
+	pfile->cb.before_define (pfile);
+
       if (_cpp_create_definition (pfile, node))
 	if (pfile->cb.define)
 	  pfile->cb.define (pfile, pfile->directive_line, node);
+
+      node->flags &= ~NODE_USED;
     }
 }
 
@@ -573,6 +578,9 @@ do_undef (cpp_reader *pfile)
 
   if (node)
     {
+      if (pfile->cb.before_define)
+	pfile->cb.before_define (pfile);
+
       if (pfile->cb.undef)
 	pfile->cb.undef (pfile, pfile->directive_line, node);
 
@@ -603,7 +611,7 @@ undefine_macros (cpp_reader *pfile ATTRIBUTE_UNUSED, cpp_hashnode *h,
   /* Body of _cpp_free_definition inlined here for speed.
      Macros and assertions no longer have anything to free.  */
   h->type = NT_VOID;
-  h->flags &= ~(NODE_POISONED|NODE_BUILTIN|NODE_DISABLED);
+  h->flags &= ~(NODE_POISONED|NODE_BUILTIN|NODE_DISABLED|NODE_USED);
   return 1;
 }
 
@@ -1638,12 +1646,26 @@ do_ifdef (cpp_reader *pfile)
 
   if (! pfile->state.skipping)
     {
-      const cpp_hashnode *node = lex_macro_node (pfile, false);
+      cpp_hashnode *node = lex_macro_node (pfile, false);
 
       if (node)
 	{
 	  skip = node->type != NT_MACRO;
 	  _cpp_mark_macro_used (node);
+	  if (!(node->flags & NODE_USED))
+	    {
+	      node->flags |= NODE_USED;
+	      if (node->type == NT_MACRO)
+		{
+		  if (pfile->cb.used_define)
+		    pfile->cb.used_define (pfile, pfile->directive_line, node);
+		}
+	      else
+		{
+		  if (pfile->cb.used_undef)
+		    pfile->cb.used_undef (pfile, pfile->directive_line, node);
+		}
+	    }
 	  check_eol (pfile);
 	}
     }
@@ -1656,7 +1678,7 @@ static void
 do_ifndef (cpp_reader *pfile)
 {
   int skip = 1;
-  const cpp_hashnode *node = 0;
+  cpp_hashnode *node = 0;
 
   if (! pfile->state.skipping)
     {
@@ -1666,6 +1688,20 @@ do_ifndef (cpp_reader *pfile)
 	{
 	  skip = node->type == NT_MACRO;
 	  _cpp_mark_macro_used (node);
+	  if (!(node->flags & NODE_USED))
+	    {
+	      node->flags |= NODE_USED;
+	      if (node->type == NT_MACRO)
+		{
+		  if (pfile->cb.used_define)
+		    pfile->cb.used_define (pfile, pfile->directive_line, node);
+		}
+	      else
+		{
+		  if (pfile->cb.used_undef)
+		    pfile->cb.used_undef (pfile, pfile->directive_line, node);
+		}
+	    }
 	  check_eol (pfile);
 	}
     }
@@ -2145,6 +2181,9 @@ cpp_pop_definition (cpp_reader *pfile, const char *str, cpp_macro *dfn)
   if (node == NULL)
     return;
 
+  if (pfile->cb.before_define)
+    pfile->cb.before_define (pfile);
+
   if (node->type == NT_MACRO)
     {
       if (pfile->cb.undef)

libcpp/expr.c

@@ -637,6 +637,20 @@ parse_defined (cpp_reader *pfile)
 		   "this use of \"defined\" may not be portable");
 
       _cpp_mark_macro_used (node);
+      if (!(node->flags & NODE_USED))
+	{
+	  node->flags |= NODE_USED;
+	  if (node->type == NT_MACRO)
+	    {
+	      if (pfile->cb.used_define)
+		pfile->cb.used_define (pfile, pfile->directive_line, node);
+	    }
+	  else
+	    {
+	      if (pfile->cb.used_undef)
+		pfile->cb.used_undef (pfile, pfile->directive_line, node);
+	    }
+	}
 
       /* A possible controlling macro of the form #if !defined ().
 	 _cpp_parse_expr checks there was no other junk on the line.  */

libcpp/include/cpplib.h

@@ -480,6 +480,14 @@ struct cpp_callbacks
      This callback receives the translated message.  */
   void (*error) (cpp_reader *, int, const char *, va_list *)
        ATTRIBUTE_FPTR_PRINTF(3,0);
+
+  /* Callbacks for when a macro is expanded, or tested (whether
+     defined or not at the time) in #ifdef, #ifndef or "defined".  */
+  void (*used_define) (cpp_reader *, unsigned int, cpp_hashnode *);
+  void (*used_undef) (cpp_reader *, unsigned int, cpp_hashnode *);
+  /* Called before #define and #undef or other macro definition
+     changes are processed.  */
+  void (*before_define) (cpp_reader *);
 };
 
 /* Chain of directories to look for include files in.  */
@@ -537,6 +545,7 @@ extern const char *progname;
 #define NODE_WARN	(1 << 4)	/* Warn if redefined or undefined.  */
 #define NODE_DISABLED	(1 << 5)	/* A disabled macro.  */
 #define NODE_MACRO_ARG	(1 << 6)	/* Used during #define processing.  */
+#define NODE_USED	(1 << 7)	/* Dumped with -dU.  */
 
 /* Different flavors of hash node.  */
 enum node_type

libcpp/macro.c

@@ -815,6 +815,13 @@ enter_macro_context (cpp_reader *pfile, cpp_hashnode *node,
 
   pfile->state.angled_headers = false;
 
+  if ((node->flags & NODE_BUILTIN) && !(node->flags & NODE_USED))
+    {
+      node->flags |= NODE_USED;
+      if (pfile->cb.used_define)
+	pfile->cb.used_define (pfile, pfile->directive_line, node);
+    }
+
   /* Handle standard macros.  */
   if (! (node->flags & NODE_BUILTIN))
     {
@@ -854,6 +861,13 @@ enter_macro_context (cpp_reader *pfile, cpp_hashnode *node,
       /* Disable the macro within its expansion.  */
       node->flags |= NODE_DISABLED;
 
+      if (!(node->flags & NODE_USED))
+	{
+	  node->flags |= NODE_USED;
+	  if (pfile->cb.used_define)
+	    pfile->cb.used_define (pfile, pfile->directive_line, node);
+	}
+
       macro->used = 1;
 
       if (macro->paramc == 0)
@@ -1393,7 +1407,7 @@ _cpp_free_definition (cpp_hashnode *h)
   /* Macros and assertions no longer have anything to free.  */
   h->type = NT_VOID;
   /* Clear builtin flag in case of redefinition.  */
-  h->flags &= ~(NODE_BUILTIN | NODE_DISABLED);
+  h->flags &= ~(NODE_BUILTIN | NODE_DISABLED | NODE_USED);
 }
 
 /* Save parameter NODE to the parameter list of macro MACRO.  Returns