mandoc: When calling an empty macro, do not clobber existing arguments.

mandoc: When calling an empty macro, do not clobber existing arguments.

[schwarze]

Log Message:
-----------
When calling an empty macro, do not clobber existing arguments.
Fixing a bug found with the groffer(1) version 1.19 manual page
following a report from Jan Stary.

Modified Files:
--------------
    mandoc:
        roff.c
    mandoc/regress/roff/de:
        Makefile

Added Files:
-----------
    mandoc/regress/roff/de:
        empty.in
        empty.out_ascii

Revision Data
-------------
Index: roff.c
===================================================================
RCS file: /home/cvs/mandoc/mandoc/roff.c,v
retrieving revision 1.364
retrieving revision 1.365
diff -Lroff.c -Lroff.c -u -p -r1.364 -r1.365
--- roff.c
+++ roff.c
@@ -3841,6 +3841,11 @@ roff_userdef(ROFF_ARGS)
 	char		 *arg, *ap, *dst, *src;
 	size_t		  sz;
 
+	/* If the macro is empty, ignore it altogether. */
+
+	if (*r->current_string == '\0')
+		return ROFF_IGN;
+
 	/* Initialize a new macro stack context. */
 
 	if (++r->mstackpos == r->mstacksz) {
@@ -3888,7 +3893,7 @@ roff_userdef(ROFF_ARGS)
 	buf->sz = strlen(buf->buf) + 1;
 	*offs = 0;
 
-	return buf->sz > 1 && buf->buf[buf->sz - 2] == '\n' ?
+	return buf->buf[buf->sz - 2] == '\n' ?
 	    ROFF_REPARSE | ROFF_USERCALL : ROFF_IGN | ROFF_APPEND;
 }
 
Index: Makefile
===================================================================
RCS file: /home/cvs/mandoc/mandoc/regress/roff/de/Makefile,v
retrieving revision 1.4
retrieving revision 1.5
diff -Lregress/roff/de/Makefile -Lregress/roff/de/Makefile -u -p -r1.4 -r1.5
--- regress/roff/de/Makefile
+++ regress/roff/de/Makefile
@@ -1,7 +1,7 @@
-# $OpenBSD: Makefile,v 1.12 2019/02/06 20:54:28 schwarze Exp $
+# $OpenBSD: Makefile,v 1.13 2019/04/21 23:45:50 schwarze Exp $
 
-REGRESS_TARGETS	 = append cond escname factorial indir infinite startde tab
-REGRESS_TARGETS	+= TH Dd
+REGRESS_TARGETS	 = append cond empty escname factorial
+REGRESS_TARGETS	+= indir infinite startde tab TH Dd
 LINT_TARGETS	 = escname indir infinite
 
 # groff-1.22.4 defect:
--- /dev/null
+++ regress/roff/de/empty.in
@@ -0,0 +1,18 @@
+.\" $OpenBSD: empty.in,v 1.1 2019/04/21 23:45:50 schwarze Exp $
+.Dd $Mdocdate: April 21 2019 $
+.Dt DE-EMPTY 1
+.Os
+.Sh NAME
+.Nm de-empty
+.Nd empty user-defined macro with arguments
+.Sh DESCRIPTION
+initial text
+.de empty
+..
+.de real
+arg=\\$1
+.empty wrong
+arg=\\$1
+..
+.real right
+final text
--- /dev/null
+++ regress/roff/de/empty.out_ascii
@@ -0,0 +1,9 @@
+DE-EMPTY(1)                 General Commands Manual                DE-EMPTY(1)
+
+N\bNA\bAM\bME\bE
+     d\bde\be-\b-e\bem\bmp\bpt\bty\by - empty user-defined macro with arguments
+
+D\bDE\bES\bSC\bCR\bRI\bIP\bPT\bTI\bIO\bON\bN
+     initial text arg=right arg=right final text
+
+OpenBSD                         April 21, 2019                         OpenBSD
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