Implement the man(7) .MR macro, a 2023 GNU extension.

The syntax and semantics is almost identical to mdoc(7) .Xr.

This will be needed for reading the groff manual pages once our port
will be updated to 1.23, and the Linux Manual Pages Project is also
determined to start using it sooner or later.  I did not advocate for
this new macro, but since we want to remain able to read all manual
pages found in the wild, there is little choice but to support it.
At least it is easy to do, they basically copied .Xr.

13 files changed, 215 insertions, 16 deletions

diff --git a/TODO b/TODO
index 46c766a9..af66e584 100644
--- a/TODO
+++ b/TODO
@@ -239,9 +239,6 @@ are mere guesses, and some may be wrong.
 
 --- missing man features -----------------------------------------------
 
-- groff_man(7) .MR
-  loc **  exist *  algo *  size *  imp ***
-
 - MANWIDTH
   Markus Waldeck <waldeck at gmx dot de> 9 Jun 2015 05:49:56 +0200
   Laura Morales <lauretas at mail dot com> 26 Apr 2018 08:15:55 +0200
diff --git a/man_html.c b/man_html.c
index 3e333e6a..46200a08 100644
--- a/man_html.c
+++ b/man_html.c
@@ -1,6 +1,6 @@
 /* $Id$ */
 /*
- * Copyright (c) 2013-2015,2017-2020,2022 Ingo Schwarze <schwarze@openbsd.org>
+ * Copyright (c) 2013-15,2017-20,2022-23 Ingo Schwarze <schwarze@openbsd.org>
  * Copyright (c) 2008-2012, 2014 Kristaps Dzonsons <kristaps@bsd.lv>
  *
  * Permission to use, copy, modify, and distribute this software for any
@@ -53,6 +53,7 @@ static	char		  list_continues(const struct roff_node *,
 static	int		  man_B_pre(MAN_ARGS);
 static	int		  man_IP_pre(MAN_ARGS);
 static	int		  man_I_pre(MAN_ARGS);
+static	int		  man_MR_pre(MAN_ARGS);
 static	int		  man_OP_pre(MAN_ARGS);
 static	int		  man_PP_pre(MAN_ARGS);
 static	int		  man_RS_pre(MAN_ARGS);
@@ -106,6 +107,7 @@ static	const struct man_html_act man_html_acts[MAN_MAX - MAN_TH] = {
 	{ NULL, NULL }, /* UE */
 	{ man_UR_pre, NULL }, /* MT */
 	{ NULL, NULL }, /* ME */
+	{ man_MR_pre, NULL }, /* MR */
 };
 
 
@@ -519,6 +521,52 @@ man_IP_pre(MAN_ARGS)
 }
 
 static int
+man_MR_pre(MAN_ARGS)
+{
+	struct tag	*t;
+	const char	*name, *section, *suffix;
+	char		*label;
+
+	html_setfont(h, ESCAPE_FONTROMAN);
+	name = section = suffix = label = NULL;
+	if (n->child != NULL) {
+		name = n->child->string;
+		if (n->child->next != NULL) {
+			section = n->child->next->string;
+			mandoc_asprintf(&label,
+			    "%s, section %s", name, section);
+			if (n->child->next->next != NULL)
+				suffix = n->child->next->next->string;
+		}
+	}
+
+	if (name != NULL && section != NULL && h->base_man1 != NULL)
+		t = print_otag(h, TAG_A, "chM?", "Xr",
+		    name, section, "aria-label", label);
+	else
+		t = print_otag(h, TAG_A, "c?", "Xr", "aria-label", label);
+
+	free(label);
+	if (name != NULL) {
+		print_text(h, name);
+		h->flags |= HTML_NOSPACE;
+	}
+	print_text(h, "(");
+	h->flags |= HTML_NOSPACE;
+	if (section != NULL) {
+		print_text(h, section);
+		h->flags |= HTML_NOSPACE;
+	}
+	print_text(h, ")");
+	print_tagq(h, t);
+	if (suffix != NULL) {
+		h->flags |= HTML_NOSPACE;
+		print_text(h, suffix);
+	}
+	return 0;
+}
+
+static int
 man_OP_pre(MAN_ARGS)
 {
 	struct tag	*tt;
diff --git a/man_macro.c b/man_macro.c
index 9840cff4..c2ea7d49 100644
--- a/man_macro.c
+++ b/man_macro.c
@@ -82,6 +82,7 @@ static const struct man_macro man_macros[MAN_MAX - MAN_TH] = {
 	{ blk_close, MAN_XSCOPE }, /* UE */
 	{ blk_exp, MAN_XSCOPE }, /* MT */
 	{ blk_close, MAN_XSCOPE }, /* ME */
+	{ in_line_eoln, 0 }, /* MR */
 };
 
 
diff --git a/man_term.c b/man_term.c
index a45a0ed2..4dac9ceb 100644
--- a/man_term.c
+++ b/man_term.c
@@ -1,6 +1,6 @@
 /* $Id$ */
 /*
- * Copyright (c) 2010-2015,2017-2020,2022 Ingo Schwarze <schwarze@openbsd.org>
+ * Copyright (c) 2010-15,2017-20,2022-23 Ingo Schwarze <schwarze@openbsd.org>
  * Copyright (c) 2008-2012 Kristaps Dzonsons <kristaps@bsd.lv>
  *
  * Permission to use, copy, modify, and distribute this software for any
@@ -74,6 +74,7 @@ static	int		  pre_DT(DECL_ARGS);
 static	int		  pre_HP(DECL_ARGS);
 static	int		  pre_I(DECL_ARGS);
 static	int		  pre_IP(DECL_ARGS);
+static	int		  pre_MR(DECL_ARGS);
 static	int		  pre_OP(DECL_ARGS);
 static	int		  pre_PD(DECL_ARGS);
 static	int		  pre_PP(DECL_ARGS);
@@ -134,6 +135,7 @@ static const struct man_term_act man_term_acts[MAN_MAX - MAN_TH] = {
 	{ NULL, NULL, 0 }, /* UE */
 	{ pre_UR, post_UR, 0 }, /* MT */
 	{ NULL, NULL, 0 }, /* ME */
+	{ pre_MR, NULL, 0 }, /* MR */
 };
 static const struct man_term_act *man_term_act(enum roff_tok);
 
@@ -328,6 +330,29 @@ pre_B(DECL_ARGS)
 }
 
 static int
+pre_MR(DECL_ARGS)
+{
+	term_fontrepl(p, TERMFONT_NONE);
+	n = n->child;
+	if (n != NULL) {
+		term_word(p, n->string);   /* name */
+		p->flags |= TERMP_NOSPACE;
+	}
+	term_word(p, "(");
+	p->flags |= TERMP_NOSPACE;
+	if (n != NULL && (n = n->next) != NULL) {
+		term_word(p, n->string);   /* section */
+		p->flags |= TERMP_NOSPACE;
+	}
+	term_word(p, ")");
+	if (n != NULL && (n = n->next) != NULL) {
+		p->flags |= TERMP_NOSPACE;
+		term_word(p, n->string);   /* suffix */
+	}
+	return 0;
+}
+
+static int
 pre_OP(DECL_ARGS)
 {
 	term_word(p, "[");
diff --git a/man_validate.c b/man_validate.c
index 722e4fdc..e3da8837 100644
--- a/man_validate.c
+++ b/man_validate.c
@@ -1,6 +1,6 @@
 /* $Id$ */
 /*
- * Copyright (c) 2010, 2012-2020 Ingo Schwarze <schwarze@openbsd.org>
+ * Copyright (c) 2010, 2012-2020, 2023 Ingo Schwarze <schwarze@openbsd.org>
  * Copyright (c) 2008, 2009, 2010, 2011 Kristaps Dzonsons <kristaps@bsd.lv>
  *
  * Permission to use, copy, modify, and distribute this software for any
@@ -33,6 +33,7 @@
 
 #include "mandoc_aux.h"
 #include "mandoc.h"
+#include "mandoc_xr.h"
 #include "roff.h"
 #include "man.h"
 #include "libmandoc.h"
@@ -54,6 +55,7 @@ static	void	  post_AT(CHKARGS);
 static	void	  post_EE(CHKARGS);
 static	void	  post_EX(CHKARGS);
 static	void	  post_IP(CHKARGS);
+static	void	  post_MR(CHKARGS);
 static	void	  post_OP(CHKARGS);
 static	void	  post_SH(CHKARGS);
 static	void	  post_TH(CHKARGS);
@@ -100,6 +102,7 @@ static	const v_check man_valids[MAN_MAX - MAN_TH] = {
 	NULL,       /* UE */
 	post_UR,    /* MT */
 	NULL,       /* ME */
+	post_MR,    /* MR */
 };
 
 
@@ -547,6 +550,32 @@ post_TH(CHKARGS)
 }
 
 static void
+post_MR(CHKARGS)
+{
+	struct roff_node *nch;
+
+	if ((nch = n->child) == NULL) {
+		mandoc_msg(MANDOCERR_NM_NONAME, n->line, n->pos, "MR");
+		return;
+	}
+	if (nch->next == NULL) {
+		mandoc_msg(MANDOCERR_XR_NOSEC,
+		    n->line, n->pos, "MR %s", nch->string);
+		return;
+	}
+	if (mandoc_xr_add(nch->next->string, nch->string, nch->line, nch->pos))
+		mandoc_msg(MANDOCERR_XR_SELF, nch->line, nch->pos,
+		    "MR %s %s", nch->string, nch->next->string);
+	if ((nch = nch->next->next) == NULL || nch->next == NULL)
+		return;
+
+	mandoc_msg(MANDOCERR_ARG_EXCESS, nch->next->line, nch->next->pos,
+	    "MR ... %s", nch->next->string);
+	while (nch->next != NULL)
+		roff_node_delete(man, nch->next);
+}
+
+static void
 post_UC(CHKARGS)
 {
 	static const char * const bsd_versions[] = {
diff --git a/mandoc.1 b/mandoc.1
index 106db4b9..780183a2 100644
--- a/mandoc.1
+++ b/mandoc.1
@@ -1,6 +1,6 @@
 .\" $Id$
 .\"
-.\" Copyright (c) 2012, 2014-2022 Ingo Schwarze <schwarze@openbsd.org>
+.\" Copyright (c) 2012, 2014-2023 Ingo Schwarze <schwarze@openbsd.org>
 .\" Copyright (c) 2009, 2010, 2011 Kristaps Dzonsons <kristaps@bsd.lv>
 .\"
 .\" Permission to use, copy, modify, and distribute this software for any
@@ -1295,9 +1295,11 @@ The same standard section title occurs more than once.
 A standard section header occurs in a section of the manual
 where it normally isn't useful.
 .It Sy "cross reference to self"
-.Pq mdoc
+.Pq mdoc , man
 An
 .Ic \&Xr
+or
+.Ic \&MR
 macro refers to a name and section matching the section of the present
 manual page and a name mentioned in an
 .Ic \&Nm
@@ -1616,12 +1618,16 @@ macro is immediately followed by an
 macro on the next input line.
 Such an empty block does not produce any output.
 .It Sy "missing section argument"
-.Pq mdoc
+.Pq mdoc , man
 An
 .Ic \&Xr
+or
+.Ic \&MR
 macro lacks its second, section number argument.
-The first argument, i.e. the name, is printed, but without subsequent
-parentheses.
+The first argument, i.e. the name, is printed, but without a section number.
+In the case of
+.Ic \&Xr ,
+the parentheses are also omitted.
 .It Sy "missing -std argument, adding it"
 .Pq mdoc
 An
@@ -2152,10 +2158,12 @@ request is neither a single ASCII character
 nor a single character escape sequence.
 All arguments are ignored and printing of a margin character is disabled.
 .It Sy "missing manual name, using \(dq\(dq"
-.Pq mdoc
+.Pq mdoc , man
 The first call to
 .Ic \&Nm ,
-or any call in the NAME section, lacks the required argument.
+or any call in the NAME section, lacks the required argument, or
+.Ic \&MR
+is called without any argument.
 .It Sy "uname(3) system call failed, using UNKNOWN"
 .Pq mdoc
 The
@@ -2283,6 +2291,8 @@ or a request of the
 family with more than two arguments
 .It
 .Ic \&Dt
+or
+.Ic \&MR
 with more than three arguments
 .It
 .Ic \&TH
diff --git a/regress/man/MR/Makefile b/regress/man/MR/Makefile
new file mode 100644
index 00000000..7ab2a9ee
--- /dev/null
+++ b/regress/man/MR/Makefile
@@ -0,0 +1,7 @@
+# $OpenBSD: Makefile,v 1.1 2023/10/24 20:30:49 schwarze Exp $
+
+# disable for now because groff changed the global indentation
+#REGRESS_TARGETS	 = basic
+LINT_TARGETS	 = basic
+
+.include <bsd.regress.mk>
diff --git a/regress/man/MR/basic.in b/regress/man/MR/basic.in
new file mode 100644
index 00000000..adb531a5
--- /dev/null
+++ b/regress/man/MR/basic.in
@@ -0,0 +1,46 @@
+.\" $OpenBSD: basic.in,v 1.1 2023/10/24 20:30:49 schwarze Exp $
+.TH MR-BASIC 1 "October 24, 2023" OpenBSD
+.SH NAME
+MR-basic \- manual page cross references
+.SH DESCRIPTION
+empty:
+.MR
+prints empty name and parentheses
+.PP
+single argument:
+.MR name
+prints empty parentheses
+.PP
+two arguments:
+.MR test 1
+normal use
+.PP
+three arguments:
+.MR test 1 suffix
+with suffix
+.PP
+four arguments:
+.MR test 1 suffix excess
+warning
+.PP
+five arguments:
+.MR test 1 suffix too many
+warning
+.PP
+after setting
+.ft B
+bold
+font:
+.MR test 1 suffix
+not bold
+.PP
+in bold next-line scope:
+.B
+.MR test 1 suffix
+not bold
+.TP 5n
+first tag
+first body
+.TP
+.MR test 1 tag
+test body
diff --git a/regress/man/MR/basic.out_ascii b/regress/man/MR/basic.out_ascii
new file mode 100644
index 00000000..d386ba0b
--- /dev/null
+++ b/regress/man/MR/basic.out_ascii
@@ -0,0 +1,29 @@
+MR-BASIC(1)                 General Commands Manual                MR-BASIC(1)
+
+NNAAMMEE
+     MR-basic - manual page cross references
+
+DDEESSCCRRIIPPTTIIOONN
+     empty: () prints empty name and parentheses
+
+     single argument: name() prints empty parentheses
+
+     two arguments: test(1) normal use
+
+     three arguments: test(1)suffix with suffix
+
+     four arguments: test(1)suffix warning
+
+     five arguments: test(1)suffix warning
+
+     after setting bboolldd ffoonntt:: test(1)suffix not bold
+
+     in bold next-line scope: test(1)suffix not bold
+
+     first tag
+          first body
+
+     test(1)tag
+          test body
+
+OpenBSD                        October 24, 2023                    MR-BASIC(1)
diff --git a/regress/man/MR/basic.out_lint b/regress/man/MR/basic.out_lint
new file mode 100644
index 00000000..d4803bcb
--- /dev/null
+++ b/regress/man/MR/basic.out_lint
@@ -0,0 +1,5 @@
+mandoc: basic.in:38:2: WARNING: line scope broken: MR breaks B
+mandoc: basic.in:7:2: ERROR: missing manual name, using "": MR
+mandoc: basic.in:11:2: WARNING: missing section argument: MR name
+mandoc: basic.in:23:19: ERROR: skipping excess arguments: MR ... excess
+mandoc: basic.in:27:19: ERROR: skipping excess arguments: MR ... too
diff --git a/regress/man/Makefile b/regress/man/Makefile
index 17a939b2..306411dc 100644
--- a/regress/man/Makefile
+++ b/regress/man/Makefile
@@ -1,6 +1,6 @@
-# $OpenBSD: Makefile,v 1.20 2022/04/27 17:04:15 schwarze Exp $
+# $OpenBSD: Makefile,v 1.21 2023/10/24 20:30:49 schwarze Exp $
 
-SUBDIR = AT B BI DT EX HP IP MT OP PD PP RS SH SS SY TH TP TS UC UR nf blank
+SUBDIR = AT B BI DT EX HP IP MR MT OP PD PP RS SH SS SY TH TP TS UC UR nf blank
 
 .include "../Makefile.sub"
 .include <bsd.subdir.mk>
diff --git a/roff.c b/roff.c
index 53f9df46..975aa471 100644
--- a/roff.c
+++ b/roff.c
@@ -367,7 +367,8 @@ const char *__roff_name[MAN_MAX + 1] = {
 	"PD",		"AT",		"in",
 	"SY",		"YS",		"OP",
 	"EX",		"EE",		"UR",
-	"UE",		"MT",		"ME",		NULL
+	"UE",		"MT",		"ME",		"MR",
+	NULL
 };
 const	char *const *roff_name = __roff_name;
 
diff --git a/roff.h b/roff.h
index b74d2280..4ebba2ec 100644
--- a/roff.h
+++ b/roff.h
@@ -476,6 +476,7 @@ enum	roff_tok {
 	MAN_UE,
 	MAN_MT,
 	MAN_ME,
+	MAN_MR,
 	MAN_MAX		/* End of man(7) macros. */
 };