mandoc: Re-classify the roff(7) \r (reverse line feed) escape sequence

mandoc: Re-classify the roff(7) \r (reverse line feed) escape sequence

[schwarze]

Log Message:
-----------
Re-classify the roff(7) \r (reverse line feed) escape sequence
from "ignore" to "unsupported" because when an input file uses it,
mandoc(1) is likely to significantly misformat the output,
usually showing parts of the output in a different order
than the author intended.

Modified Files:
--------------
    mandoc:
        roff.7
        roff_escape.c
    mandoc/regress/roff/esc:
        Makefile

Added Files:
-----------
    mandoc/regress/roff/esc:
        r.in
        r.out_ascii
        r.out_lint

Revision Data
-------------
Index: roff.7
===================================================================
RCS file: /home/cvs/mandoc/mandoc/roff.7,v
retrieving revision 1.116
retrieving revision 1.117
diff -Lroff.7 -Lroff.7 -u -p -r1.116 -r1.117
--- roff.7
+++ roff.7
@@ -1,7 +1,7 @@
-.\"	$Id$
+.\" $Id$
 .\"
+.\" Copyright (c) 2010-2019, 2022 Ingo Schwarze <schwarze@openbsd.org>
 .\" Copyright (c) 2010, 2011, 2012 Kristaps Dzonsons <kristaps@bsd.lv>
-.\" Copyright (c) 2010-2019 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
@@ -2166,8 +2166,8 @@ Break the output line at the end of the 
 Set number register; ignored by
 .Xr mandoc 1 .
 .It Ic \er
-Move up by one line; ignored by
-.Xr mandoc 1 .
+Reverse line feed: move up by one output line.
+Currently unsupported.
 .It Ic \eS\(aq Ns Ar number Ns Ic \(aq
 Slant output; ignored by
 .Xr mandoc 1 .
Index: roff_escape.c
===================================================================
RCS file: /home/cvs/mandoc/mandoc/roff_escape.c,v
retrieving revision 1.1
retrieving revision 1.2
diff -Lroff_escape.c -Lroff_escape.c -u -p -r1.1 -r1.2
--- roff_escape.c
+++ roff_escape.c
@@ -103,6 +103,7 @@ roff_escape(const char *buf, const int l
 
 	case '!':
 	case '?':
+	case 'r':
 		rval = ESCAPE_UNSUPP;
 		goto out;
 
@@ -114,7 +115,6 @@ roff_escape(const char *buf, const int l
 	case '^':
 	case 'a':
 	case 'd':
-	case 'r':
 	case 't':
 	case 'u':
 	case '{':
--- /dev/null
+++ regress/roff/esc/r.out_lint
@@ -0,0 +1 @@
+mandoc: r.in:11:7: UNSUPP: unsupported escape sequence: \r
--- /dev/null
+++ regress/roff/esc/r.out_ascii
@@ -0,0 +1,11 @@
+ESC-R(1)                    General Commands Manual                   ESC-R(1)
+
+N\bNA\bAM\bME\bE
+     e\bes\bsc\bc-\b-r\br - the roff reverse line feed escape sequence
+
+D\bDE\bES\bSC\bCR\bRI\bIP\bPT\bTI\bIO\bON\bN
+     first line
+     beforeafter
+     last line
+
+OpenBSD                          May 20, 2022                          OpenBSD
Index: Makefile
===================================================================
RCS file: /home/cvs/mandoc/mandoc/regress/roff/esc/Makefile,v
retrieving revision 1.10
retrieving revision 1.11
diff -Lregress/roff/esc/Makefile -Lregress/roff/esc/Makefile -u -p -r1.10 -r1.11
--- regress/roff/esc/Makefile
+++ regress/roff/esc/Makefile
@@ -1,15 +1,16 @@
-# $OpenBSD: Makefile,v 1.20 2022/05/01 16:18:59 schwarze Exp $
+# $OpenBSD: Makefile,v 1.21 2022/05/20 13:06:27 schwarze Exp $
 
 REGRESS_TARGETS	 = one two multi comment
-REGRESS_TARGETS	+= B bs_man bs_mdoc c c_man E1 e f h hneg l O1 o p w z
+REGRESS_TARGETS	+= B bs_man bs_mdoc c c_man E1 e f h hneg l O1 o p r w z
 REGRESS_TARGETS	+= ignore invalid unsupp
 HTML_TARGETS	 = f
-LINT_TARGETS	 = comment B h l O1 w ignore invalid unsupp
+LINT_TARGETS	 = comment B h l O1 r w ignore invalid unsupp
 
-# mandoc defect:
+# mandoc defects:
 # - \h with a negative argument replaces output characters
 #   instead of overstriking them
+# - \r does not return to the previous output line
 
-SKIP_GROFF	 = hneg
+SKIP_GROFF	 = hneg r
 
 .include <bsd.regress.mk>
--- /dev/null
+++ regress/roff/esc/r.in
@@ -0,0 +1,13 @@
+.\" $OpenBSD: r.in,v 1.1 2022/05/20 13:06:27 schwarze Exp $
+.Dd $Mdocdate: May 20 2022 $
+.Dt ESC-R 1
+.Os
+.Sh NAME
+.Nm esc-r
+.Nd the roff reverse line feed escape sequence
+.Sh DESCRIPTION
+.Bd -literal
+first line
+before\rafter
+last line
+.Ed
--
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