commit 4a3f20bceee7cef125f9a88bab32439f9fe4f773
from: Neven Sajko <nsajko@gmail.com>
via: Russ Cox <rsc@golang.org>
date: Mon Jan 13 19:41:28 2020 UTC

cmd/yacc: do not create an out of bounds pointer

An out of bounds pointer/array index being created is an error in
standard C.

Updates #313

Change-Id: I7108fcde1a8e03017e9ab852adb737940489c827

commit - 7ba9f9467d95fa8d05bb04d36fd4c602e497f529
commit + 4a3f20bceee7cef125f9a88bab32439f9fe4f773
blob - 32990f62beea56c9df70c3315e0cc2260a7cd166
blob + 5db36d04b419e0e4a9596c0aee1060f1bbfd370d
--- src/cmd/yacc.c
+++ src/cmd/yacc.c
@@ -2819,8 +2819,9 @@ stin(int i)
 	for(n = -maxoff; n < ACTSIZE; n++) {
 		flag = 0;
 		for(r = q1; r < q2; r += 2) {
-			if((s = *r + n + amem) < amem)
+			if(*r + n < 0)
 				goto nextn;
+			s = *r + n + amem;
 			if(*s == 0)
 				flag++;
 			else