diff --git a/bin/sh/memalloc.c b/bin/sh/memalloc.c
index 2571a7ea11af..3ee104c4cc4e 100644
--- a/bin/sh/memalloc.c
+++ b/bin/sh/memalloc.c
@@ -127,7 +127,7 @@ static struct stack_block *stackp;
 static struct stackmark *markp;
 char *stacknxt;
 int stacknleft;
-int sstrnleft;
+char *sstrend;
 
 
 static void
@@ -146,6 +146,7 @@ stnewblock(int nbytes)
 	sp->prev = stackp;
 	stacknxt = SPACE(sp);
 	stacknleft = allocsize - (stacknxt - (char*)sp);
+	sstrend = stacknxt + stacknleft;
 	stackp = sp;
 	INTON;
 }
@@ -204,6 +205,7 @@ popstackmark(struct stackmark *mark)
 	}
 	stacknxt = mark->stacknxt;
 	stacknleft = mark->stacknleft;
+	sstrend = stacknxt + stacknleft;
 	INTON;
 }
 
@@ -250,6 +252,7 @@ growstackblock(int min)
 		stackp = sp;
 		stacknxt = SPACE(sp);
 		stacknleft = newlen - (stacknxt - (char*)sp);
+		sstrend = stacknxt + stacknleft;
 
 		/*
 		 * Stack marks pointing to the start of the old block
@@ -306,7 +309,6 @@ static char *
 growstrstackblock(int n, int min)
 {
 	growstackblock(min);
-	sstrnleft = stackblocksize() - n;
 	return stackblock() + n;
 }
 
@@ -325,31 +327,20 @@ growstackstr(void)
  */
 
 char *
-makestrspace(int min)
+makestrspace(int min, char *p)
 {
 	int len;
 
-	len = stackblocksize() - sstrnleft;
+	len = p - stackblock();
 	return (growstrstackblock(len, min));
 }
 
 
-
-void
-ungrabstackstr(char *s, char *p)
-{
-	stacknleft += stacknxt - s;
-	stacknxt = s;
-	sstrnleft = stacknleft - (p - s);
-}
-
-
 char *
 stputbin(const char *data, int len, char *p)
 {
 	CHECKSTRSPACE(len, p);
 	memcpy(p, data, len);
-	sstrnleft -= len;
 	return (p + len);
 }
 
diff --git a/bin/sh/memalloc.h b/bin/sh/memalloc.h
index fcdd5baf5c46..f3e8829eed4f 100644
--- a/bin/sh/memalloc.h
+++ b/bin/sh/memalloc.h
@@ -45,7 +45,7 @@ struct stackmark {
 
 extern char *stacknxt;
 extern int stacknleft;
-extern int sstrnleft;
+extern char *sstrend;
 
 pointer ckmalloc(size_t);
 pointer ckrealloc(pointer, int);
@@ -57,8 +57,7 @@ void setstackmark(struct stackmark *);
 void popstackmark(struct stackmark *);
 void grabstackblock(int);
 char *growstackstr(void);
-char *makestrspace(int);
-void ungrabstackstr(char *, char *);
+char *makestrspace(int, char *);
 char *stputbin(const char *data, int len, char *p);
 char *stputs(const char *data, char *p);
 
@@ -66,10 +65,10 @@ char *stputs(const char *data, char *p);
 
 #define stackblock() stacknxt
 #define stackblocksize() stacknleft
-#define STARTSTACKSTR(p)	p = stackblock(), sstrnleft = stackblocksize()
-#define STPUTC(c, p)	(--sstrnleft >= 0? (*p++ = (c)) : (p = growstackstr(), --sstrnleft, *p++ = (c)))
-#define CHECKSTRSPACE(n, p)	{ if (sstrnleft < n) p = makestrspace(n); }
-#define USTPUTC(c, p)	(--sstrnleft, *p++ = (c))
+#define STARTSTACKSTR(p)	p = stackblock()
+#define STPUTC(c, p)	do { if (p == sstrend) p = growstackstr(); *p++ = (c); } while(0)
+#define CHECKSTRSPACE(n, p)	{ if (sstrend - p < n) p = makestrspace(n, p); }
+#define USTPUTC(c, p)	(*p++ = (c))
 /*
  * STACKSTRNUL's use is where we want to be able to turn a stack
  * (non-sentinel, character counting string) into a C string,
@@ -77,10 +76,11 @@ char *stputs(const char *data, char *p);
  * Note: Because of STACKSTRNUL's semantics, STACKSTRNUL cannot be used
  * on a stack that will grabstackstr()ed.
  */
-#define STACKSTRNUL(p)	(sstrnleft == 0? (p = growstackstr(), *p = '\0') : (*p = '\0'))
-#define STUNPUTC(p)	(++sstrnleft, --p)
+#define STACKSTRNUL(p)	(p == sstrend ? (p = growstackstr(), *p = '\0') : (*p = '\0'))
+#define STUNPUTC(p)	(--p)
 #define STTOPC(p)	p[-1]
-#define STADJUST(amount, p)	(p += (amount), sstrnleft -= (amount))
-#define grabstackstr(p)	stalloc(stackblocksize() - sstrnleft)
+#define STADJUST(amount, p)	(p += (amount))
+#define grabstackstr(p)	stalloc((char *)p - stackblock())
+#define ungrabstackstr(s, p)	stunalloc((s))
 #define STPUTBIN(s, len, p)	p = stputbin((s), (len), p)
 #define STPUTS(s, p)	p = stputs((s), p)