util: Avoid localised underflow

Avoid parenthesising an unsigned subtraction that can be negative and,
therefore, underflow.  There is no need for the parentheses and
removing them results in an expression that is evaluated left-to-right
and can not underflow.

It isn't clear that the underflow matters.  lp <= ls, so if (li - lp)
underflows then ls + (li - lp) will always overflow.  This should
produce the correct answer.  However, depending on this seems wrong.

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>

diff --git a/lib/util/substitute.c b/lib/util/substitute.c
index 2249035f7047ee8ff71f2bb3a0f15e42c2c9f295..0ddab17958847143d630939dc1921b151aa48982 100644 (file)
--- a/lib/util/substitute.c
+++ b/lib/util/substitute.c
@@ -65,10 +65,10 @@ static void string_sub2(char *s,const char *pattern, const char *insert, size_t
                len = ls + 1; /* len is number of *bytes* */
 
        while (lp <= ls && (p = strstr_m(s,pattern))) {
-               if (ls + (li-lp) >= len) {
+               if (ls + li - lp >= len) {
                        DEBUG(0,("ERROR: string overflow by "
                                "%d in string_sub(%.50s, %d)\n",
-                                (int)(ls + (li-lp) - len),
+                                (int)(ls + li - lp - len),
                                 pattern, (int)len));
                        break;
                }
@@ -105,7 +105,7 @@ static void string_sub2(char *s,const char *pattern, const char *insert, size_t
                        }
                }
                s = p + li;
-               ls += (li-lp);
+               ls = ls + li - lp;
 
                if (replace_once)
                        break;
@@ -192,10 +192,10 @@ _PUBLIC_ void all_string_sub(char *s,const char *pattern,const char *insert, siz
                len = ls + 1; /* len is number of *bytes* */
 
        while (lp <= ls && (p = strstr_m(s,pattern))) {
-               if (ls + (li-lp) >= len) {
+               if (ls + li - lp >= len) {
                        DEBUG(0,("ERROR: string overflow by "
                                "%d in all_string_sub(%.50s, %d)\n",
-                                (int)(ls + (li-lp) - len),
+                                (int)(ls + li - lp - len),
                                 pattern, (int)len));
                        break;
                }
@@ -204,6 +204,6 @@ _PUBLIC_ void all_string_sub(char *s,const char *pattern,const char *insert, siz
                }
                memcpy(p, insert, li);
                s = p + li;
-               ls += (li-lp);
+               ls = ls + li - lp;
        }
 }