Reset HTML formatter state, in particular the id_unique hash,

after processing each manual page, such that the next page
starts from a clean state and doesn't continue suffix numbering.

Issue found while looking at Debian/debiman#48
which was brought up by Orestis Ioannou <oorestisime at github>.

usr.bin/mandoc/html.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: html.c,v 1.123 2019/03/01 10:48:58 schwarze Exp $ */
+/*	$OpenBSD: html.c,v 1.124 2019/03/03 13:01:47 schwarze Exp $ */
 /*
  * Copyright (c) 2008-2011, 2014 Kristaps Dzonsons <kristaps@bsd.lv>
  * Copyright (c) 2011-2015, 2017-2019 Ingo Schwarze <schwarze@openbsd.org>
@@ -108,6 +108,7 @@ static	const struct htmldata htmltags[TAG_MAX] = {
 /* Avoid duplicate HTML id= attributes. */
 static	struct ohash	 id_unique;
 
+static	void	 html_reset_internal(struct html *);
 static	void	 print_byte(struct html *, char);
 static	void	 print_endword(struct html *);
 static	void	 print_indent(struct html *);
@@ -143,21 +144,17 @@ html_alloc(const struct manoutput *outopts)
 	return h;
 }
 
-void
-html_free(void *p)
+static void
+html_reset_internal(struct html *h)
 {
 	struct tag	*tag;
-	struct html	*h;
 	char		*cp;
 	unsigned int	 slot;
 
-	h = (struct html *)p;
 	while ((tag = h->tag) != NULL) {
 		h->tag = tag->next;
 		free(tag);
 	}
-	free(h);
-
 	cp = ohash_first(&id_unique, &slot);
 	while (cp != NULL) {
 		free(cp);
@@ -166,6 +163,20 @@ html_free(void *p)
 	ohash_delete(&id_unique);
 }
 
+void
+html_reset(void *p)
+{
+	html_reset_internal(p);
+	mandoc_ohash_init(&id_unique, 4, 0);
+}
+
+void
+html_free(void *p)
+{
+	html_reset_internal(p);
+	free(p);
+}
+
 void
 print_gen_head(struct html *h)
 {

usr.bin/mandoc/main.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: main.c,v 1.221 2019/01/11 17:03:43 schwarze Exp $ */
+/*	$OpenBSD: main.c,v 1.222 2019/03/03 13:01:47 schwarze Exp $ */
 /*
  * Copyright (c) 2008-2012 Kristaps Dzonsons <kristaps@bsd.lv>
  * Copyright (c) 2010-2012, 2014-2019 Ingo Schwarze <schwarze@openbsd.org>
@@ -805,6 +805,8 @@ parse(struct curparse *curp, int fd, const char *file)
 
 	if (curp->outdata == NULL)
 		outdata_alloc(curp);
+	else if (curp->outtype == OUTT_HTML)
+		html_reset(curp);
 
 	mandoc_xr_reset();
 	meta = mparse_result(curp->mp);

usr.bin/mandoc/main.h

@@ -1,7 +1,7 @@
-/*	$OpenBSD: main.h,v 1.24 2018/12/30 00:48:47 schwarze Exp $ */
+/*	$OpenBSD: main.h,v 1.25 2019/03/03 13:01:47 schwarze Exp $ */
 /*
  * Copyright (c) 2009, 2010, 2011 Kristaps Dzonsons <kristaps@bsd.lv>
- * Copyright (c) 2014, 2015 Ingo Schwarze <schwarze@openbsd.org>
+ * Copyright (c) 2014, 2015, 2019 Ingo Schwarze <schwarze@openbsd.org>
  *
  * Permission to use, copy, modify, and distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
@@ -29,6 +29,7 @@ struct	manoutput;
 void		 *html_alloc(const struct manoutput *);
 void		  html_mdoc(void *, const struct roff_meta *);
 void		  html_man(void *, const struct roff_meta *);
+void		  html_reset(void *);
 void		  html_free(void *);
 
 void		  tree_mdoc(void *, const struct roff_meta *);