Bug 1431874 - Loop using a size_t index, not a pointer, to avoid undefined behavior computing an end pointer possibly outside the range of the underlying data. r=jonco

--HG--
extra : rebase_source : c877adc843c2e269742735f9af203278dfe9a973

js/src/ctypes/CTypes.cpp

@@ -3208,9 +3208,10 @@ template<class CharType>
 static size_t
 strnlen(const CharType* begin, size_t max)
 {
-  for (const CharType* s = begin; s != begin + max; ++s)
-    if (*s == 0)
-      return s - begin;
+  for (size_t i = 0; i < max; i++) {
+    if (begin[i] == '\0')
+      return i;
+  }
 
   return max;
 }