Using an undefined string or macro will cause it to be defined as empty.

Observed by Werner Lemberg on Nov 14, 2011
and rotting on my TODO list ever since.

6 files changed, 193 insertions, 50 deletions

diff --git a/TODO b/TODO
index 0128fc3d..4d74fd06 100644
--- a/TODO
+++ b/TODO
@@ -1,6 +1,6 @@
 ************************************************************************
 * Official mandoc TODO.
-* $Id: TODO,v 1.248 2017/10/28 16:20:24 schwarze Exp $
+* $Id: TODO,v 1.249 2018/04/09 02:31:42 schwarze Exp $
 ************************************************************************
 
 Many issues are annotated for difficulty as follows:
@@ -87,10 +87,6 @@ are mere guesses, and some may be wrong.
   Found by naddy@ in devel/cutils cobfusc(1)  Mon, 16 Feb 2015 19:10:52 +0100
   loc ***  exist ***  algo ***  size **  imp *
 
-- using undefined strings or macros defines them to be empty
-  wl@  Mon, 14 Nov 2011 14:37:01 +0000
-  loc *  exist *  algo *  size *  imp *
-
 --- missing mdoc features ----------------------------------------------
 
 - .Bl -column .Xo support is missing
diff --git a/regress/roff/string/Makefile b/regress/roff/string/Makefile
index 354a7a75..eda8c8ad 100644
--- a/regress/roff/string/Makefile
+++ b/regress/roff/string/Makefile
@@ -1,7 +1,7 @@
 # $OpenBSD: Makefile,v 1.6 2014/07/06 19:08:57 schwarze Exp $
 
-REGRESS_TARGETS	 = escape infinite name std zerolength
-LINT_TARGETS	 = name std
+REGRESS_TARGETS	 = escape infinite name std undef zerolength
+LINT_TARGETS	 = name std undef
 
 # The infinite test fails badly with groff-1.20.1:
 # It fails to print the following text.
diff --git a/regress/roff/string/undef.in b/regress/roff/string/undef.in
new file mode 100644
index 00000000..d84a67c6
--- /dev/null
+++ b/regress/roff/string/undef.in
@@ -0,0 +1,69 @@
+.\" $OpenBSD: std.in,v 1.2 2017/07/04 14:53:27 schwarze Exp $
+.TH STRING-UNDEF 1 "April 9, 2018"
+.SH NAME
+string-undef - expanding undefined strings
+.SH DESCRIPTION
+.SS User defined string
+The sting "mys" is
+.ie dmys defined
+.el undefined
+and remains
+.ie dmys defined.
+.el undefined.
+.PP
+Its value is "\*[mys]", and now it is
+.ie dmys defined,
+.el undefined,
+and its value is still "\*[mys]".
+.PP
+.ds mys newval
+After redefining it to "\*[mys]", it is of course still
+.ie dmys defined.
+.el undefined.
+.PP
+.rm mys
+After removing the definition, it is now
+.ie dmys defined.
+.el undefined.
+.SS User defined macro
+The macro "mym" is
+.ie dmym defined.
+.el undefined.
+.PP
+It has no effect:
+.mym
+But now it is
+.ie dmym defined.
+.el undefined.
+.PP
+.de mym
+neweffect
+..
+After defining it as:
+.mym
+it is of course still
+.ie dmym defined.
+.el undefined.
+.PP
+.rm mym
+After removing the definition, it is now
+.ie dmym defined.
+.el undefined.
+.SS Renamed macro
+The standard .BR macro is
+.ie dBR defined,
+.el undefined,
+and it
+.BR works .
+.PP
+.rn BR newBR
+After renaming it, the new name is
+.ie dnewBR defined,
+.el undefined,
+and
+.newBR works .
+.SS Predefined string
+A predefined string is
+.ie dR defined
+.el undefined
+and has the value "\*R".
diff --git a/regress/roff/string/undef.out_ascii b/regress/roff/string/undef.out_ascii
new file mode 100644
index 00000000..6e7bd01f
--- /dev/null
+++ b/regress/roff/string/undef.out_ascii
@@ -0,0 +1,37 @@
+STRING-UNDEF(1)             General Commands Manual            STRING-UNDEF(1)
+
+
+
+NNAAMMEE
+       string-undef - expanding undefined strings
+
+DDEESSCCRRIIPPTTIIOONN
+   UUsseerr ddeeffiinneedd ssttrriinngg
+       The sting "mys" is undefined and remains undefined.
+
+       Its value is "", and now it is defined, and its value is still "".
+
+       After redefining it to "newval", it is of course still defined.
+
+       After removing the definition, it is now undefined.
+
+   UUsseerr ddeeffiinneedd mmaaccrroo
+       The macro "mym" is undefined.
+
+       It has no effect: But now it is defined.
+
+       After defining it as: neweffect it is of course still defined.
+
+       After removing the definition, it is now undefined.
+
+   RReennaammeedd mmaaccrroo
+       The standard .BR macro is defined, and it wwoorrkkss.
+
+       After renaming it, the new name is defined, and wwoorrkkss.
+
+   PPrreeddeeffiinneedd ssttrriinngg
+       A predefined string is defined and has the value "(R)".
+
+
+
+OpenBSD                          April 9, 2018                 STRING-UNDEF(1)
diff --git a/regress/roff/string/undef.out_lint b/regress/roff/string/undef.out_lint
new file mode 100644
index 00000000..320ec604
--- /dev/null
+++ b/regress/roff/string/undef.out_lint
@@ -0,0 +1,2 @@
+mandoc: undef.in:14:15: WARNING: undefined string, using "": mys
+mandoc: undef.in:34:2: ERROR: skipping unknown macro: .mym
diff --git a/roff.c b/roff.c
index e2e498da..2a609eaf 100644
--- a/roff.c
+++ b/roff.c
@@ -1,7 +1,7 @@
-/*	$Id: roff.c,v 1.324 2017/07/14 17:16:16 schwarze Exp $ */
+/*	$Id: roff.c,v 1.325 2018/04/09 02:31:42 schwarze Exp $ */
 /*
  * Copyright (c) 2008-2012, 2014 Kristaps Dzonsons <kristaps@bsd.lv>
- * Copyright (c) 2010-2015, 2017 Ingo Schwarze <schwarze@openbsd.org>
+ * Copyright (c) 2010-2015, 2017, 2018 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
@@ -46,6 +46,7 @@
 #define	ROFFDEF_STD	(1 << 4)  /* mdoc(7) or man(7) macro. */
 #define	ROFFDEF_ANY	(ROFFDEF_USER | ROFFDEF_PRE | \
 			 ROFFDEF_REN | ROFFDEF_STD)
+#define	ROFFDEF_UNDEF	(1 << 5)  /* Completely undefined. */
 
 /* --- data types --------------------------------------------------------- */
 
@@ -185,7 +186,7 @@ static	int		 roff_getregn(const struct roff *,
 				const char *, size_t);
 static	int		 roff_getregro(const struct roff *,
 				const char *name);
-static	const char	*roff_getstrn(const struct roff *,
+static	const char	*roff_getstrn(struct roff *,
 				const char *, size_t, int *);
 static	int		 roff_hasregn(const struct roff *,
 				const char *, size_t);
@@ -1639,6 +1640,11 @@ roff_parse(struct roff *r, char *buf, int *pos, int ln, int ppos)
 	}
 	if (t != TOKEN_NONE)
 		*pos = cp - buf;
+	else if (deftype == ROFFDEF_UNDEF) {
+		/* Using an undefined macro defines it to be empty. */
+		roff_setstrn(&r->strtab, mac, maclen, "", 0, 0);
+		roff_setstrn(&r->rentab, mac, maclen, NULL, 0, 0);
+	}
 	return t;
 }
 
@@ -3537,62 +3543,95 @@ roff_setstrn(struct roffkv **r, const char *name, size_t namesz,
 }
 
 static const char *
-roff_getstrn(const struct roff *r, const char *name, size_t len,
+roff_getstrn(struct roff *r, const char *name, size_t len,
     int *deftype)
 {
 	const struct roffkv	*n;
-	int			 i;
+	int			 found, i;
 	enum roff_tok		 tok;
 
-	if (*deftype & ROFFDEF_USER) {
-		for (n = r->strtab; n != NULL; n = n->next) {
-			if (strncmp(name, n->key.p, len) == 0 &&
-			    n->key.p[len] == '\0' &&
-			    n->val.p != NULL) {
-				*deftype = ROFFDEF_USER;
-				return n->val.p;
-			}
+	found = 0;
+	for (n = r->strtab; n != NULL; n = n->next) {
+		if (strncmp(name, n->key.p, len) != 0 ||
+		    n->key.p[len] != '\0' || n->val.p == NULL)
+			continue;
+		if (*deftype & ROFFDEF_USER) {
+			*deftype = ROFFDEF_USER;
+			return n->val.p;
+		} else {
+			found = 1;
+			break;
 		}
 	}
-	if (*deftype & ROFFDEF_PRE) {
-		for (i = 0; i < PREDEFS_MAX; i++) {
-			if (strncmp(name, predefs[i].name, len) == 0 &&
-			    predefs[i].name[len] == '\0') {
-				*deftype = ROFFDEF_PRE;
-				return predefs[i].str;
-			}
+	for (n = r->rentab; n != NULL; n = n->next) {
+		if (strncmp(name, n->key.p, len) != 0 ||
+		    n->key.p[len] != '\0' || n->val.p == NULL)
+			continue;
+		if (*deftype & ROFFDEF_REN) {
+			*deftype = ROFFDEF_REN;
+			return n->val.p;
+		} else {
+			found = 1;
+			break;
 		}
 	}
-	if (*deftype & ROFFDEF_REN) {
-		for (n = r->rentab; n != NULL; n = n->next) {
-			if (strncmp(name, n->key.p, len) == 0 &&
-			    n->key.p[len] == '\0' &&
-			    n->val.p != NULL) {
-				*deftype = ROFFDEF_REN;
-				return n->val.p;
-			}
+	for (i = 0; i < PREDEFS_MAX; i++) {
+		if (strncmp(name, predefs[i].name, len) != 0 ||
+		    predefs[i].name[len] != '\0')
+			continue;
+		if (*deftype & ROFFDEF_PRE) {
+			*deftype = ROFFDEF_PRE;
+			return predefs[i].str;
+		} else {
+			found = 1;
+			break;
 		}
 	}
-	if (*deftype & ROFFDEF_STD) {
-		if (r->man->macroset != MACROSET_MAN) {
-			for (tok = MDOC_Dd; tok < MDOC_MAX; tok++) {
-				if (strncmp(name, roff_name[tok], len) == 0 &&
-				    roff_name[tok][len] == '\0') {
-					*deftype = ROFFDEF_STD;
-					return NULL;
-				}
+	if (r->man->macroset != MACROSET_MAN) {
+		for (tok = MDOC_Dd; tok < MDOC_MAX; tok++) {
+			if (strncmp(name, roff_name[tok], len) != 0 ||
+			    roff_name[tok][len] != '\0')
+				continue;
+			if (*deftype & ROFFDEF_STD) {
+				*deftype = ROFFDEF_STD;
+				return NULL;
+			} else {
+				found = 1;
+				break;
 			}
 		}
-		if (r->man->macroset != MACROSET_MDOC) {
-			for (tok = MAN_TH; tok < MAN_MAX; tok++) {
-				if (strncmp(name, roff_name[tok], len) == 0 &&
-				    roff_name[tok][len] == '\0') {
-					*deftype = ROFFDEF_STD;
-					return NULL;
-				}
+	}
+	if (r->man->macroset != MACROSET_MDOC) {
+		for (tok = MAN_TH; tok < MAN_MAX; tok++) {
+			if (strncmp(name, roff_name[tok], len) != 0 ||
+			    roff_name[tok][len] != '\0')
+				continue;
+			if (*deftype & ROFFDEF_STD) {
+				*deftype = ROFFDEF_STD;
+				return NULL;
+			} else {
+				found = 1;
+				break;
 			}
 		}
 	}
+
+	if (found == 0 && *deftype != ROFFDEF_ANY) {
+		if (*deftype & ROFFDEF_REN) {
+			/*
+			 * This might still be a request,
+			 * so do not treat it as undefined yet.
+			 */
+			*deftype = ROFFDEF_UNDEF;
+			return NULL;
+		}
+
+		/* Using an undefined string defines it to be empty. */
+
+		roff_setstrn(&r->strtab, name, len, "", 0, 0);
+		roff_setstrn(&r->rentab, name, len, NULL, 0, 0);
+	}
+
 	*deftype = 0;
 	return NULL;
 }