Allow preprocessor-like directives.  These keywords were already
defined in locale/programs/locfile-kw.h, an implementation for
'define', 'undef', 'ifdef', 'else' and 'endif' is now provided in
locale/programs/ld-collate.c.  For the moment, 'ifndef' and 'elif'
are not implemented because they do not appear in locfile-kw.h.
This patch is harmless, it only adds new keywords.

# DP: Dpatch author: Denis Barbier
# DP: Patch author: Denis Barbier
# DP: Upstream status: BZ686
# DP: Date: 2006-01-08

---
 locale/programs/ld-collate.c |  275 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 275 insertions(+)

--- a/locale/programs/ld-collate.c
+++ b/locale/programs/ld-collate.c
@@ -163,6 +163,24 @@
   size_t line;
 };
 
+/* Data type for toggles.  */
+struct toggle_list_t;
+
+struct toggle_list_t
+{
+  const char *name;
+
+  /* Predecessor in the list.  */
+  struct toggle_list_t *last;
+
+  /* This flag is set when a keyword is undefined.  */
+  int is_undefined;
+
+  /* Where does the branch come from.  */
+  const char *file;
+  size_t line;
+};
+
 /* Sparse table of struct element_t *.  */
 #define TABLE wchead_table
 #define ELEMENT struct element_t *
@@ -218,6 +236,9 @@
   /* This value is used when handling ellipsis.  */
   struct element_t ellipsis_weight;
 
+  /* This is a stack of .  */
+  struct toggle_list_t *flow_control;
+
   /* Known collating elements.  */
   hash_table elem_table;
 
@@ -1466,6 +1487,56 @@
 }
 
 
+static struct token *
+flow_skip (struct linereader *ldfile, const struct charmap_t *charmap,
+	   struct locale_collate_t *collate)
+{
+  int level = 0;
+  struct token *now;
+  enum token_t nowtok;
+  while (1)
+    {
+      lr_ignore_rest (ldfile, 0);
+      now = lr_token (ldfile, charmap, NULL, NULL, 0);
+      nowtok = now->tok;
+      if (nowtok == tok_eof)
+	break;
+      else if (nowtok == tok_ifdef || nowtok == tok_ifndef)
+	++level ;
+      else if (nowtok == tok_else)
+	{
+	  if (strcmp (collate->flow_control->name, "else") == 0)
+	    lr_error (ldfile,
+		      _("%s: `else' statement at `%s:%Zu' cannot be followed by another `else' statement"),
+		      "LC_COLLATE", collate->flow_control->name, collate->flow_control->line);
+	  if (level == 0)
+	    {
+	      collate->flow_control->name = "else";
+	      collate->flow_control->file = ldfile->fname;
+	      collate->flow_control->line = ldfile->lineno;
+	      break;
+	    }
+	}
+      else if (nowtok == tok_endif)
+	{
+	  if (level == 0)
+	    {
+	      collate->flow_control = collate->flow_control->last;
+	      break;
+	    }
+	  --level ;
+	}
+    }
+  if (nowtok == tok_eof)
+    WITH_CUR_LOCALE (error (0, 0, _("\
+%s: unterminated `%s' flow control beginning at %s:%Zu"),
+				 "LC_COLLATE", collate->flow_control->name,
+				 collate->flow_control->file,
+				 collate->flow_control->line));
+  return now;
+}
+
+
 static void
 collate_startup (struct linereader *ldfile, struct localedef_t *locale,
 		 struct localedef_t *copy_locale, int ignore_content)
@@ -2511,6 +2582,8 @@
   */
   int state = 0;
 
+  static struct toggle_list_t *defined_keywords = NULL;
+
   /* Get the repertoire we have to use.  */
   if (repertoire_name != NULL)
     repertoire = repertoire_read (repertoire_name);
@@ -2525,6 +2598,82 @@
 	}
       while (nowtok == tok_eol);
 
+  while (nowtok == tok_define || nowtok == tok_undef)
+    {
+      /* Ignore the rest of the line if we don't need the input of
+         this line.  */
+      if (ignore_content)
+        {
+          lr_ignore_rest (ldfile, 0);
+          now = lr_token (ldfile, charmap, result, NULL, verbose);
+          nowtok = now->tok;
+          continue;
+        }
+
+      arg = lr_token (ldfile, charmap, result, NULL, verbose);
+      if (arg->tok != tok_ident)
+        goto err_label;
+
+      if (nowtok == tok_define)
+        {
+	  struct toggle_list_t *runp = defined_keywords;
+	  char *name;
+
+	  while (runp != NULL)
+	    if (strncmp (runp->name, arg->val.str.startmb,
+	    	     arg->val.str.lenmb) == 0
+	        && runp->name[arg->val.str.lenmb] == '\0')
+              SYNTAX_ERROR (_("%s: syntax error"), "LC_COLLATE");
+	    else
+	      runp = runp->last;
+
+	  if (runp != NULL && runp->is_undefined == 0)
+	    {
+	      lr_ignore_rest (ldfile, 0);
+              SYNTAX_ERROR (_("%s: syntax error"), "LC_COLLATE");
+	    }
+
+	  if (runp == NULL)
+	    {
+	      runp = (struct toggle_list_t *) xcalloc (1, sizeof (*runp));
+	      runp->last = defined_keywords;
+	      defined_keywords = runp;
+	    }
+	  else
+	    {
+	      free ((char *) runp->name);
+	      runp->is_undefined = 0;
+	    }
+
+	  name = (char *) xmalloc (arg->val.str.lenmb + 1);
+	  memcpy (name, arg->val.str.startmb, arg->val.str.lenmb);
+	  name[arg->val.str.lenmb] = '\0';
+	  runp->name = name;
+        }
+      else
+        {
+	  struct toggle_list_t *runp = defined_keywords;
+	  while (runp != NULL)
+	    if (strncmp (runp->name, arg->val.str.startmb,
+	    	     arg->val.str.lenmb) == 0
+	        && runp->name[arg->val.str.lenmb] == '\0')
+	    {
+	      runp->is_undefined = 1;
+              SYNTAX_ERROR (_("%s: syntax error"), "LC_COLLATE");
+	    }
+	    else
+	      runp = runp->last;
+        }
+
+      lr_ignore_rest (ldfile, 1);
+      do
+        {
+          now = lr_token (ldfile, charmap, result, NULL, verbose);
+          nowtok = now->tok;
+        }
+      while (nowtok == tok_eol);
+    }
+
   if (nowtok == tok_copy)
     {
       now = lr_token (ldfile, charmap, result, NULL, verbose);
@@ -3679,6 +3828,125 @@
 			  repertoire, result, nowtok);
 	  break;
 
+	case tok_ifdef:
+	  /* Ignore the rest of the line if we don't need the input of
+	     this line.  */
+	  if (ignore_content)
+	    {
+	      lr_ignore_rest (ldfile, 0);
+	      break;
+	    }
+
+	  arg = lr_token (ldfile, charmap, result, NULL, verbose);
+	  if (arg->tok != tok_ident)
+	    goto err_label;
+	  else
+	    {
+	      struct toggle_list_t *runp = defined_keywords;
+	      struct toggle_list_t *flow = (struct toggle_list_t *) xcalloc (1, sizeof (*runp));
+	      flow->name = "ifdef";
+	      flow->file = ldfile->fname;
+	      flow->line = ldfile->lineno;
+	      flow->last = collate->flow_control;
+	      collate->flow_control = flow;
+
+	      while (runp != NULL)
+		if (strncmp (runp->name, arg->val.str.startmb,
+			     arg->val.str.lenmb) == 0
+		    && runp->name[arg->val.str.lenmb] == '\0')
+		  break;
+		else
+		  runp = runp->last;
+
+	      if (runp == NULL)
+		{
+		  now = flow_skip(ldfile, charmap, collate);
+		  if (now->tok == tok_eof)
+		    WITH_CUR_LOCALE (error (0, 0, _("\
+%s: unterminated `%s' flow control"), "LC_COLLATE", collate->flow_control->name));
+		}
+	    }
+	  lr_ignore_rest (ldfile, 1);
+	  break;
+
+	case tok_ifndef:
+	  /* Ignore the rest of the line if we don't need the input of
+	     this line.  */
+	  if (ignore_content)
+	    {
+	      lr_ignore_rest (ldfile, 0);
+	      break;
+	    }
+
+	  arg = lr_token (ldfile, charmap, result, NULL, verbose);
+	  if (arg->tok != tok_ident)
+	    goto err_label;
+	  else
+	    {
+	      struct toggle_list_t *runp = defined_keywords;
+	      struct toggle_list_t *flow = (struct toggle_list_t *) xcalloc (1, sizeof (*runp));
+	      flow->name = "ifndef";
+	      flow->file = ldfile->fname;
+	      flow->line = ldfile->lineno;
+	      flow->last = collate->flow_control;
+	      collate->flow_control = flow;
+
+	      while (runp != NULL)
+		if (strncmp (runp->name, arg->val.str.startmb,
+			     arg->val.str.lenmb) == 0
+		    && runp->name[arg->val.str.lenmb] == '\0')
+		  break;
+		else
+		  runp = runp->last;
+
+	      if (runp != NULL)
+		{
+		  now = flow_skip(ldfile, charmap, collate);
+		  if (now->tok == tok_eof)
+		    WITH_CUR_LOCALE (error (0, 0, _("\
+%s: unterminated `%s' flow control"), "LC_COLLATE", collate->flow_control->name));
+		}
+	    }
+	  lr_ignore_rest (ldfile, 1);
+	  break;
+
+	case tok_else:
+	  /* Ignore the rest of the line if we don't need the input of
+	     this line.  */
+	  if (ignore_content)
+	    {
+	      lr_ignore_rest (ldfile, 0);
+	      break;
+	    }
+
+	  if (strcmp (collate->flow_control->name, "else") == 0)
+	    lr_error (ldfile,
+		      _("%s: `else' statement at `%s:%Zu' cannot be followed by another `else' statement"),
+		      "LC_COLLATE", collate->flow_control->name, collate->flow_control->line);
+	  collate->flow_control->name = "else";
+	  collate->flow_control->file = ldfile->fname;
+	  collate->flow_control->line = ldfile->lineno;
+	  now = flow_skip(ldfile, charmap, collate);
+	  if (now->tok == tok_eof)
+	    WITH_CUR_LOCALE (error (0, 0, _("\
+%s: unterminated `%s' flow control"), "LC_COLLATE", collate->flow_control->name));
+	  break;
+
+	case tok_endif:
+	  /* Ignore the rest of the line if we don't need the input of
+	     this line.  */
+	  if (ignore_content)
+	    {
+	      lr_ignore_rest (ldfile, 0);
+	      break;
+	    }
+
+	  if (collate->flow_control == NULL)
+	    goto err_label;
+	  else
+	    collate->flow_control = collate->flow_control->last;
+	  break;
+
 	case tok_end:
 	  /* Next we assume `LC_COLLATE'.  */
 	  if (!ignore_content)
@@ -3708,6 +3976,13 @@
 	      else if (state == 5)
 		WITH_CUR_LOCALE (error (0, 0, _("\
 %s: missing `reorder-sections-end' keyword"), "LC_COLLATE"));
+	      if (collate->flow_control != NULL
+		  && strcmp(collate->flow_control->file, ldfile->fname) == 0)
+		WITH_CUR_LOCALE (error (0, 0, _("\
+%s: unterminated `%s' flow control beginning at %s:%Zu"),
+				 "LC_COLLATE", collate->flow_control->name,
+				 collate->flow_control->file,
+				 collate->flow_control->line));
 	    }
 	  arg = lr_token (ldfile, charmap, result, NULL, verbose);
 	  if (arg->tok == tok_eof)