Fully implement the \B (validate numerical expression) and

partially implement the \w (measure text width) escape sequence
in a way that makes them usable in numerical expressions and in
conditional requests, similar to how \n (interpolate number register)
and \* (expand user-defined string) are implemented.

This lets mandoc(1) handle the baroque low-level roff code
found at the beginning of the ggrep(1) manual.
Thanks to pascal@ for the report.

8 files changed, 175 insertions, 44 deletions

diff --git a/regress/usr.bin/mandoc/roff/esc/B.in b/regress/usr.bin/mandoc/roff/esc/B.in
new file mode 100644
index 00000000000..84b0f9f157c
--- /dev/null
+++ b/regress/usr.bin/mandoc/roff/esc/B.in
@@ -0,0 +1,34 @@
+.Dd April 8, 2014
+.Dt ESC-B 1
+.Os OpenBSD
+.Sh NAME
+.Nm esc-B
+.Nd the roff escape B sequence: validate numerical expression
+.Sh DESCRIPTION
+empty: \B''
+.br
+digit: \B'0'
+.br
+no number: \B'no number'
+.br
+trailing garbage: \B'1X'
+.br
+trailing operator: \B'1+'
+.br
+infix operator: \B'1+1'
+.br
+infix and trailing operator: \B'1+1+'
+.br
+chain of operations: \B'1+2+3+4'
+.br
+trailing para: \B'1+('
+.br
+unclosed para: \B'(1'
+.br
+empty pair of parentheses: \B'()'
+.br
+parentheses containing number: \B'(42)'
+.br
+complex expression: \B'3+(3*(5==5*2)*4)+(3*5)/2'
+.br
+other delimiter: \Bx1+1x
diff --git a/regress/usr.bin/mandoc/roff/esc/B.out_ascii b/regress/usr.bin/mandoc/roff/esc/B.out_ascii
new file mode 100644
index 00000000000..6ea3246655d
--- /dev/null
+++ b/regress/usr.bin/mandoc/roff/esc/B.out_ascii
@@ -0,0 +1,22 @@
+ESC-B(1)                   OpenBSD Reference Manual                   ESC-B(1)
+
+NNAAMMEE
+     eesscc--BB - the roff escape B sequence: validate numerical expression
+
+DDEESSCCRRIIPPTTIIOONN
+     empty: 0
+     digit: 1
+     no number: 0
+     trailing garbage: 0
+     trailing operator: 0
+     infix operator: 1
+     infix and trailing operator: 0
+     chain of operations: 1
+     trailing para: 0
+     unclosed para: 0
+     empty pair of parentheses: 0
+     parentheses containing number: 1
+     complex expression: 1
+     other delimiter: 1
+
+OpenBSD                          April 8, 2014                         OpenBSD
diff --git a/regress/usr.bin/mandoc/roff/esc/Makefile b/regress/usr.bin/mandoc/roff/esc/Makefile
index e9705972a80..4fb16774431 100644
--- a/regress/usr.bin/mandoc/roff/esc/Makefile
+++ b/regress/usr.bin/mandoc/roff/esc/Makefile
@@ -1,6 +1,6 @@
-# $OpenBSD: Makefile,v 1.3 2012/05/28 22:45:34 schwarze Exp $
+# $OpenBSD: Makefile,v 1.4 2014/04/08 01:36:50 schwarze Exp $
 
-REGRESS_TARGETS=one two multi c f h z ignore
+REGRESS_TARGETS = one two multi B c f h w z ignore
 
 # Postprocessing to remove "character backspace" sequences
 # unless they are foolowed by the same character again.
diff --git a/regress/usr.bin/mandoc/roff/esc/w.in b/regress/usr.bin/mandoc/roff/esc/w.in
new file mode 100644
index 00000000000..bd93623e464
--- /dev/null
+++ b/regress/usr.bin/mandoc/roff/esc/w.in
@@ -0,0 +1,14 @@
+.Dd April 8, 2014
+.Dt ESC-W 1
+.Os OpenBSD
+.Sh NAME
+.Nm esc-w
+.Nd the roff escape w sequence: text width
+.Sh DESCRIPTION
+empty: \w''
+.br
+character: \w'n'
+.br
+blank: \w' '
+.br
+text: \w'text'
diff --git a/regress/usr.bin/mandoc/roff/esc/w.out_ascii b/regress/usr.bin/mandoc/roff/esc/w.out_ascii
new file mode 100644
index 00000000000..4b11f621f51
--- /dev/null
+++ b/regress/usr.bin/mandoc/roff/esc/w.out_ascii
@@ -0,0 +1,12 @@
+ESC-W(1)                   OpenBSD Reference Manual                   ESC-W(1)
+
+NNAAMMEE
+     eesscc--ww - the roff escape w sequence: text width
+
+DDEESSCCRRIIPPTTIIOONN
+     empty: 0
+     character: 24
+     blank: 24
+     text: 96
+
+OpenBSD                          April 8, 2014                         OpenBSD
diff --git a/share/man/man7/roff.7 b/share/man/man7/roff.7
index 39019cd2195..577817788fb 100644
--- a/share/man/man7/roff.7
+++ b/share/man/man7/roff.7
@@ -1,4 +1,4 @@
-.\"	$OpenBSD: roff.7,v 1.32 2014/04/07 15:05:12 schwarze Exp $
+.\"	$OpenBSD: roff.7,v 1.33 2014/04/08 01:36:50 schwarze Exp $
 .\"
 .\" Copyright (c) 2010, 2011, 2012 Kristaps Dzonsons <kristaps@bsd.lv>
 .\" Copyright (c) 2010, 2011, 2013, 2014 Ingo Schwarze <schwarze@openbsd.org>
@@ -15,7 +15,7 @@
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"
-.Dd $Mdocdate: April 7 2014 $
+.Dd $Mdocdate: April 8 2014 $
 .Dt ROFF 7
 .Os
 .Sh NAME
@@ -1170,10 +1170,15 @@ Digit width space character.
 Anchor definition; ignored by
 .Xr mandoc 1 .
 .Ss \eB\(aq Ns Ar string Ns \(aq
-Test whether
+Interpolate
+.Sq 1
+if
 .Ar string
-is a numerical expession; ignored by
-.Xr mandoc 1 .
+conforms to the syntax of
+.Sx Numerical expressions
+explained above and
+.Sq 0
+otherwise.
 .Ss \eb\(aq Ns Ar string Ns \(aq
 Bracket building function; ignored by
 .Xr mandoc 1 .
@@ -1297,9 +1302,13 @@ Vertical motion; ignored by
 .Xr mandoc 1 .
 .Ss \ew\(aq Ns Ar string Ns \(aq
 Interpolate the width of the
-.Ar string ;
-ignored by
-.Xr mandoc 1 .
+.Ar string .
+The
+.Xr mandoc 1
+implementation assumes that after expansion of user-defined strings, the
+.Ar string
+only contains normal characters, no escape sequences, and that each
+character has a width of 24 basic units.
 .Ss \eX\(aq Ns Ar string Ns \(aq
 Output
 .Ar string
diff --git a/usr.bin/mandoc/mandoc.c b/usr.bin/mandoc/mandoc.c
index f7a70ee0ae0..627f64e6be9 100644
--- a/usr.bin/mandoc/mandoc.c
+++ b/usr.bin/mandoc/mandoc.c
@@ -1,7 +1,7 @@
-/*	$Id: mandoc.c,v 1.46 2014/04/07 17:50:43 schwarze Exp $ */
+/*	$Id: mandoc.c,v 1.47 2014/04/08 01:36:50 schwarze Exp $ */
 /*
  * Copyright (c) 2008, 2009, 2010, 2011 Kristaps Dzonsons <kristaps@bsd.lv>
- * Copyright (c) 2011, 2012, 2013 Ingo Schwarze <schwarze@openbsd.org>
+ * Copyright (c) 2011, 2012, 2013, 2014 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
@@ -157,21 +157,18 @@ mandoc_escape(const char **end, const char **start, int *sz)
 	/*
 	 * These escapes are of the form \X'Y', where 'X' is the trigger
 	 * and 'Y' is any string.  These have opaque sub-strings.
+	 * The \B and \w escapes are handled in roff.c, roff_res().
 	 */
 	case ('A'):
 		/* FALLTHROUGH */
 	case ('b'):
 		/* FALLTHROUGH */
-	case ('B'):
-		/* FALLTHROUGH */
 	case ('D'):
 		/* FALLTHROUGH */
 	case ('o'):
 		/* FALLTHROUGH */
 	case ('R'):
 		/* FALLTHROUGH */
-	case ('w'):
-		/* FALLTHROUGH */
 	case ('X'):
 		/* FALLTHROUGH */
 	case ('Z'):
diff --git a/usr.bin/mandoc/roff.c b/usr.bin/mandoc/roff.c
index d80d6cf5986..1320bf7d111 100644
--- a/usr.bin/mandoc/roff.c
+++ b/usr.bin/mandoc/roff.c
@@ -1,4 +1,4 @@
-/*	$Id: roff.c,v 1.78 2014/04/07 21:00:00 schwarze Exp $ */
+/*	$Id: roff.c,v 1.79 2014/04/08 01:36:50 schwarze Exp $ */
 /*
  * Copyright (c) 2010, 2011, 2012 Kristaps Dzonsons <kristaps@bsd.lv>
  * Copyright (c) 2010-2014 Ingo Schwarze <schwarze@openbsd.org>
@@ -481,9 +481,9 @@ roff_alloc(struct mparse *parse, int options)
 }
 
 /*
- * In the current line, expand user-defined strings ("\*")
- * and references to number registers ("\n").
- * Also check the syntax of other escape sequences.
+ * In the current line, expand escape sequences that tend to get
+ * used in numerical expressions and conditional requests.
+ * Also check the syntax of the remaining escape sequences.
  */
 static enum rofferr
 roff_res(struct roff *r, char **bufp, size_t *szp, int ln, int pos)
@@ -499,6 +499,9 @@ roff_res(struct roff *r, char **bufp, size_t *szp, int ln, int pos)
 	size_t		 naml;	/* actual length of the escape name */
 	size_t		 ressz;	/* size of the replacement string */
 	int		 expand_count;	/* to avoid infinite loops */
+	int		 npos;	/* position in numeric expression */
+	int		 irc;	/* return code from roff_evalnum() */
+	char		 term;	/* character terminating the escape */
 
 	expand_count = 0;
 	start = *bufp + pos;
@@ -521,16 +524,19 @@ roff_res(struct roff *r, char **bufp, size_t *szp, int ln, int pos)
 			continue;
 		}
 
-		/*
-		 * Everything except user-defined strings and number
-		 * registers is only checked, not expanded.
-		 */
+		/* Decide whether to expand or to check only. */
 
+		term = '\0';
 		cp = stesc + 1;
 		switch (*cp) {
 		case ('*'):
 			res = NULL;
 			break;
+		case ('B'):
+			/* FALLTHROUGH */
+		case ('w'):
+			term = cp[1];
+			/* FALLTHROUGH */
 		case ('n'):
 			res = ubuf;
 			break;
@@ -553,20 +559,27 @@ roff_res(struct roff *r, char **bufp, size_t *szp, int ln, int pos)
 		 * Save a pointer to the name.
 		 */
 
-		switch (*++cp) {
-		case ('\0'):
-			continue;
-		case ('('):
-			cp++;
-			maxl = 2;
-			break;
-		case ('['):
-			cp++;
+		if ('\0' == term) {
+			switch (*++cp) {
+			case ('\0'):
+				maxl = 0;
+				break;
+			case ('('):
+				cp++;
+				maxl = 2;
+				break;
+			case ('['):
+				cp++;
+				term = ']';
+				maxl = 0;
+				break;
+			default:
+				maxl = 1;
+				break;
+			}
+		} else {
+			cp += 2;
 			maxl = 0;
-			break;
-		default:
-			maxl = 1;
-			break;
 		}
 		stnam = cp;
 
@@ -578,10 +591,12 @@ roff_res(struct roff *r, char **bufp, size_t *szp, int ln, int pos)
 					(MANDOCERR_BADESCAPE, 
 					 r->parse, ln, 
 					 (int)(stesc - *bufp), NULL);
-				continue;
+				break;
 			}
-			if (0 == maxl && ']' == *cp)
+			if (0 == maxl && *cp == term) {
+				cp++;
 				break;
+			}
 		}
 
 		/*
@@ -589,11 +604,26 @@ roff_res(struct roff *r, char **bufp, size_t *szp, int ln, int pos)
 		 * undefined, resume searching for escapes.
 		 */
 
-		if (NULL == res)
+		switch (stesc[1]) {
+		case ('*'):
 			res = roff_getstrn(r, stnam, naml);
-		else
+			break;
+		case ('B'):
+			npos = 0;
+			irc = roff_evalnum(stnam, &npos, NULL, 0);
+			ubuf[0] = irc && stnam + npos + 1 == cp
+			    ? '1' : '0';
+			ubuf[1] = '\0';
+			break;
+		case ('n'):
 			snprintf(ubuf, sizeof(ubuf), "%d",
 			    roff_getregn(r, stnam, naml));
+			break;
+		case ('w'):
+			snprintf(ubuf, sizeof(ubuf), "%d",
+			    24 * (int)naml);
+			break;
+		}
 
 		if (NULL == res) {
 			mandoc_msg
@@ -610,7 +640,7 @@ roff_res(struct roff *r, char **bufp, size_t *szp, int ln, int pos)
 
 		strlcpy(nbuf, *bufp, (size_t)(stesc - *bufp + 1));
 		strlcat(nbuf, res, *szp);
-		strlcat(nbuf, cp + (maxl ? 0 : 1), *szp);
+		strlcat(nbuf, cp, *szp);
 
 		/* Prepare for the next replacement. */
 
@@ -1122,7 +1152,10 @@ roff_cond_text(ROFF_ARGS)
 static int
 roff_getnum(const char *v, int *pos, int *res)
 {
-	int p, n;
+	int	 myres, n, p;
+
+	if (NULL == res)
+		res = &myres;
 
 	p = *pos;
 	n = v[p] == '-';
@@ -1426,9 +1459,16 @@ roff_evalpar(const char *v, int *pos, int *res)
 	if ( ! roff_evalnum(v, pos, res, 1))
 		return(0);
 
-	/* If the trailing parenthesis is missing, ignore the error. */
+	/*
+	 * Omission of the closing parenthesis
+	 * is an error in validation mode,
+	 * but ignored in evaluation mode.
+	 */
+
 	if (')' == v[*pos])
 		(*pos)++;
+	else if (NULL == res)
+		return(0);
 
 	return(1);
 }
@@ -1474,6 +1514,9 @@ roff_evalnum(const char *v, int *pos, int *res, int skipwhite)
 			while (isspace((unsigned char)v[*pos]))
 				(*pos)++;
 
+		if (NULL == res)
+			continue;
+
 		switch (operator) {
 		case ('+'):
 			*res += operand2;