Fix overflow check in StringInfo; add missing casts

A few thinkos I introduced in fa2fa9955280.  Also, amend a similarly
broken comment.

Report by Daniel Vérité.
Authors: Daniel Vérité, Álvaro Herrera
Discussion: https://postgr.es/m/1706e85e-60d2-494e-8a64-9af1e1b2186e@manitou-mail.org

diff --git a/src/backend/lib/stringinfo.c b/src/backend/lib/stringinfo.c
index bdc204edf77e56533f6f897c6a0c11f58c426727..3eee49beb6270aab957c83fcc5b5282c3327b42a 100644 (file)
--- a/src/backend/lib/stringinfo.c
+++ b/src/backend/lib/stringinfo.c
@@ -313,19 +313,20 @@ enlargeStringInfo(StringInfo str, int needed)
         * for efficiency, double the buffer size each time it overflows.
         * Actually, we might need to more than double it if 'needed' is big...
         */
-       newlen = 2 * str->maxlen;
-       while (needed > newlen)
+       newlen = 2 * (Size) str->maxlen;
+       while ((Size) needed > newlen)
                newlen = 2 * newlen;
 
        /*
-        * Clamp to the limit in case we went past it.  Note we are assuming here
-        * that limit <= INT_MAX/2, else the above loop could overflow.  We will
-        * still have newlen >= needed.
+        * Clamp to the limit in case we went past it.  (We used to depend on
+        * limit <= INT32_MAX/2, to avoid overflow in the loop above; we no longer
+        * depend on that, but if "needed" and str->maxlen ever become wider, we
+        * will need similar caution here.)  We will still have newlen >= needed.
         */
        if (newlen > limit)
                newlen = limit;
 
-       str->data = (char *) repalloc_huge(str->data, (Size) newlen);
+       str->data = (char *) repalloc_huge(str->data, newlen);
 
        str->maxlen = newlen;
 }