Split tagging into a validation part including prioritization

in tag.{h,c} and {mdoc,man}_validate.c
and into a formatting part including command line argument checking
in term_tag.{h,c}, html.c, and {mdoc|man}_{term|html}.c.

Immediate functional benefits include:
* Improved prioritization of automatic tags for .Em and .Sy.
* Avoiding bogus automatic tags when .Em, .Fn, or .Sy are explicitly tagged.
* Explicit tagging of .Er and .Fl now works in HTML output.
* Automatic tagging of .IP and .TP now works in HTML output.
But mainly, this patch provides clean earth to build further improvements on.

Technical changes:
* Main program: Write a tag file for ASCII and UTF-8 output only.
* All formatters: There is no more need to delay writing the tags.
* mdoc(7)+man(7) formatters: No more need for elaborate syntax tree inspection.
* HTML formatter: If available, use the "string" attribute as the tag.
* HTML formatter: New function to write permalinks, to reduce code duplication.

Style cleanup in the vicinity while here:
* mdoc(7) terminal formatter: To set up bold font for children,
defer to termp_bold_pre() rather than calling term_fontpush() manually.
* mdoc(7) terminal formatter: Garbage collect some duplicate functions.
* mdoc(7) HTML formatter: Unify <code> handling, delete redundant functions.
* Where possible, use switch statements rather than if cascades.
* Get rid of some more Yoda notation.

The necessity for such changes was first discussed with kn@, but i didn't
bother him with a request to review the resulting -673/+782 line patch.

1 files changed, 206 insertions, 0 deletions

diff --git a/term_tag.c b/term_tag.c
new file mode 100644
index 00000000..cb9fa16d
--- /dev/null
+++ b/term_tag.c
@@ -0,0 +1,206 @@
+/* $Id: term_tag.c,v 1.1 2020/03/13 15:32:29 schwarze Exp $ */
+/*
+ * Copyright (c) 2015,2016,2018,2019,2020 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
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ * Functions to write a ctags(1) file.
+ * For use by the mandoc(1) ASCII and UTF-8 formatters only.
+ */
+#include "config.h"
+
+#include <sys/types.h>
+
+#include <errno.h>
+#include <signal.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "mandoc.h"
+#include "roff.h"
+#include "tag.h"
+#include "term_tag.h"
+
+static void tag_signal(int) __attribute__((__noreturn__));
+
+static struct tag_files tag_files;
+
+
+/*
+ * Prepare for using a pager.
+ * Not all pagers are capable of using a tag file,
+ * but for simplicity, create it anyway.
+ */
+struct tag_files *
+term_tag_init(char *tagname)
+{
+	struct sigaction	 sa;
+	int			 ofd;	/* In /tmp/, dup(2)ed to stdout. */
+	int			 tfd;
+
+	ofd = tfd = -1;
+	tag_files.tfs = NULL;
+	tag_files.tcpgid = -1;
+	tag_files.tagname = tagname;
+
+	/* Clean up when dying from a signal. */
+
+	memset(&sa, 0, sizeof(sa));
+	sigfillset(&sa.sa_mask);
+	sa.sa_handler = tag_signal;
+	sigaction(SIGHUP, &sa, NULL);
+	sigaction(SIGINT, &sa, NULL);
+	sigaction(SIGTERM, &sa, NULL);
+
+	/*
+	 * POSIX requires that a process calling tcsetpgrp(3)
+	 * from the background gets a SIGTTOU signal.
+	 * In that case, do not stop.
+	 */
+
+	sa.sa_handler = SIG_IGN;
+	sigaction(SIGTTOU, &sa, NULL);
+
+	/* Save the original standard output for use by the pager. */
+
+	if ((tag_files.ofd = dup(STDOUT_FILENO)) == -1) {
+		mandoc_msg(MANDOCERR_DUP, 0, 0, "%s", strerror(errno));
+		goto fail;
+	}
+
+	/* Create both temporary output files. */
+
+	(void)strlcpy(tag_files.ofn, "/tmp/man.XXXXXXXXXX",
+	    sizeof(tag_files.ofn));
+	(void)strlcpy(tag_files.tfn, "/tmp/man.XXXXXXXXXX",
+	    sizeof(tag_files.tfn));
+	if ((ofd = mkstemp(tag_files.ofn)) == -1) {
+		mandoc_msg(MANDOCERR_MKSTEMP, 0, 0,
+		    "%s: %s", tag_files.ofn, strerror(errno));
+		goto fail;
+	}
+	if ((tfd = mkstemp(tag_files.tfn)) == -1) {
+		mandoc_msg(MANDOCERR_MKSTEMP, 0, 0,
+		    "%s: %s", tag_files.tfn, strerror(errno));
+		goto fail;
+	}
+	if ((tag_files.tfs = fdopen(tfd, "w")) == NULL) {
+		mandoc_msg(MANDOCERR_FDOPEN, 0, 0, "%s", strerror(errno));
+		goto fail;
+	}
+	tfd = -1;
+	if (dup2(ofd, STDOUT_FILENO) == -1) {
+		mandoc_msg(MANDOCERR_DUP, 0, 0, "%s", strerror(errno));
+		goto fail;
+	}
+	close(ofd);
+	return &tag_files;
+
+fail:
+	term_tag_unlink();
+	if (ofd != -1)
+		close(ofd);
+	if (tfd != -1)
+		close(tfd);
+	if (tag_files.ofd != -1) {
+		close(tag_files.ofd);
+		tag_files.ofd = -1;
+	}
+	tag_files.tagname = NULL;
+	return NULL;
+}
+
+void
+term_tag_write(struct roff_node *n, size_t line)
+{
+	const char	*cp;
+	int		 len;
+
+	if (tag_files.tfs == NULL)
+		return;
+	if (n->string == NULL)
+		n = n->child;
+	cp = n->string;
+	if (cp[0] == '\\' && (cp[1] == '&' || cp[1] == 'e'))
+		cp += 2;
+	len = strcspn(cp, " \t\\");
+	fprintf(tag_files.tfs, "%.*s %s %zu\n",
+	    len, cp, tag_files.ofn, line);
+}
+
+void
+term_tag_finish(void)
+{
+	if (tag_files.tfs == NULL)
+		return;
+	fclose(tag_files.tfs);
+	tag_files.tfs = NULL;
+	switch (tag_check(tag_files.tagname)) {
+	case TAG_EMPTY:
+		unlink(tag_files.tfn);
+		*tag_files.tfn = '\0';
+		/* FALLTHROUGH */
+	case TAG_MISS:
+		if (tag_files.tagname == NULL)
+			break;
+		mandoc_msg(MANDOCERR_TAG, 0, 0, "%s", tag_files.tagname);
+		tag_files.tagname = NULL;
+		break;
+	case TAG_OK:
+		break;
+	}
+}
+
+void
+term_tag_unlink(void)
+{
+	pid_t	 tc_pgid;
+
+	if (tag_files.tcpgid != -1) {
+		tc_pgid = tcgetpgrp(tag_files.ofd);
+		if (tc_pgid == tag_files.pager_pid ||
+		    tc_pgid == getpgid(0) ||
+		    getpgid(tc_pgid) == -1)
+			(void)tcsetpgrp(tag_files.ofd, tag_files.tcpgid);
+	}
+	if (*tag_files.ofn != '\0') {
+		unlink(tag_files.ofn);
+		*tag_files.ofn = '\0';
+	}
+	if (*tag_files.tfn != '\0') {
+		unlink(tag_files.tfn);
+		*tag_files.tfn = '\0';
+	}
+	if (tag_files.tfs != NULL) {
+		fclose(tag_files.tfs);
+		tag_files.tfs = NULL;
+	}
+}
+
+static void
+tag_signal(int signum)
+{
+	struct sigaction	 sa;
+
+	term_tag_unlink();
+	memset(&sa, 0, sizeof(sa));
+	sigemptyset(&sa.sa_mask);
+	sa.sa_handler = SIG_DFL;
+	sigaction(signum, &sa, NULL);
+	kill(getpid(), signum);
+	/* NOTREACHED */
+	_exit(1);
+}