Store a pointer to "null" in struct ndblock's defn member instead of a

duplicate allocated on the heap; the address defn points to is significant,
and is checked against the address of "null" in certain conditionals.

PR:		59883
MFC after:	1 week

3 files changed, 6 insertions, 6 deletions

diff --git a/usr.bin/m4/eval.c b/usr.bin/m4/eval.c
index 6d2d0fde..060ce03 100644
--- a/usr.bin/m4/eval.c
+++ b/usr.bin/m4/eval.c
@@ -593,12 +593,12 @@ dodefine(const char *name, const char *defn)
 			p->type = n & TYPEMASK;
 			if ((n & NOARGS) == 0)
 				p->type |= NEEDARGS;
-			p->defn = xstrdup(null);
+			p->defn = null;
 			return;
 		}
 	}
 	if (!*defn)
-		p->defn = xstrdup(null);
+		p->defn = null;
 	else
 		p->defn = xstrdup(defn);
 	p->type = MACRTYPE;
@@ -645,7 +645,7 @@ dopushdef(const char *name, const char *defn)
 		    CURRENT_LINE);
 	p = addent(name);
 	if (!*defn)
-		p->defn = xstrdup(null);
+		p->defn = null;
 	else
 		p->defn = xstrdup(defn);
 	p->type = MACRTYPE;
diff --git a/usr.bin/m4/extern.h b/usr.bin/m4/extern.h
index 88cba41..e96870b 100644
--- a/usr.bin/m4/extern.h
+++ b/usr.bin/m4/extern.h
@@ -149,7 +149,7 @@ extern char ecommt[MAXCCHARS+1];/* end character for comment */
 extern char *ep;		/* first free char in strspace */
 extern char lquote[MAXCCHARS+1];/* left quote character (`) */
 extern const char *m4wraps;	/* m4wrap string default. */
-extern const char *null;	/* as it says.. just a null. */
+extern char null[];		/* as it says.. just a null. */
 extern char rquote[MAXCCHARS+1];/* right quote character (') */
 extern char scommt[MAXCCHARS+1];/* start character for comment */
 extern int synccpp;		/* Line synchronisation for C preprocessor */
diff --git a/usr.bin/m4/main.c b/usr.bin/m4/main.c
index 1c1ac45..847a372 100644
--- a/usr.bin/m4/main.c
+++ b/usr.bin/m4/main.c
@@ -93,7 +93,7 @@ int maxout;
 FILE *active;			/* active output file pointer  */
 int ilevel = 0; 		/* input file stack pointer    */
 int oindex = 0; 		/* diversion index..	       */
-const char *null = "";          /* as it says.. just a null..  */
+char null[] = "";		/* as it says.. just a null..  */
 const char *m4wraps = "";       /* m4wrap string default..     */
 char lquote[MAXCCHARS+1] = {LQUOTE};	/* left quote character  (`)   */
 char rquote[MAXCCHARS+1] = {RQUOTE};	/* right quote character (')   */
@@ -583,7 +583,7 @@ initkwds(void)
 		p->nxtptr = hashtab[h % HASHSIZE];
 		hashtab[h % HASHSIZE] = p;
 		p->name = xstrdup(keywrds[i].knam);
-		p->defn = xstrdup(null);
+		p->defn = null;
 		p->hv = h;
 		p->type = keywrds[i].ktyp & TYPEMASK;
 		if ((keywrds[i].ktyp & NOARGS) == 0)