Make pqexpbuffer a little more robust, per bug report from Heinz Ekker.

diff --git a/src/interfaces/libpq/pqexpbuffer.c b/src/interfaces/libpq/pqexpbuffer.c
index 623ec8306e565e4cc9fcd5940a85778fc930909a..523c78fcea93323d37cc5d34b2240611f3935c26 100644 (file)
--- a/src/interfaces/libpq/pqexpbuffer.c
+++ b/src/interfaces/libpq/pqexpbuffer.c
@@ -17,7 +17,7 @@
  * Portions Copyright (c) 1996-2000, PostgreSQL, Inc
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Header: /cvsroot/pgsql/src/interfaces/libpq/pqexpbuffer.c,v 1.6 2000/04/12 17:17:15 momjian Exp $
+ * $Header: /cvsroot/pgsql/src/interfaces/libpq/pqexpbuffer.c,v 1.7 2001/01/19 19:39:23 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -99,6 +99,9 @@ termPQExpBuffer(PQExpBuffer str)
                free(str->data);
                str->data = NULL;
        }
+       /* just for luck, make the buffer validly empty. */
+       str->maxlen = 0;
+       str->len = 0;
 }
 
 /*------------------------
@@ -139,7 +142,7 @@ enlargePQExpBuffer(PQExpBuffer str, size_t needed)
         * overflows. Actually, we might need to more than double it if
         * 'needed' is big...
         */
-       newlen = str->maxlen ? (2 * str->maxlen) : 64;
+       newlen = (str->maxlen > 0) ? (2 * str->maxlen) : 64;
        while (needed > newlen)
                newlen = 2 * newlen;
 
@@ -177,9 +180,9 @@ printfPQExpBuffer(PQExpBuffer str, const char *fmt,...)
                 * just fall through to enlarge the buffer first.
                 *----------
                 */
-               avail = str->maxlen - str->len - 1;
-               if (avail > 16)
+               if (str->maxlen > str->len + 16)
                {
+                       avail = str->maxlen - str->len - 1;
                        va_start(args, fmt);
                        nprinted = vsnprintf(str->data + str->len, avail,
                                                                 fmt, args);
@@ -226,9 +229,9 @@ appendPQExpBuffer(PQExpBuffer str, const char *fmt,...)
                 * just fall through to enlarge the buffer first.
                 *----------
                 */
-               avail = str->maxlen - str->len - 1;
-               if (avail > 16)
+               if (str->maxlen > str->len + 16)
                {
+                       avail = str->maxlen - str->len - 1;
                        va_start(args, fmt);
                        nprinted = vsnprintf(str->data + str->len, avail,
                                                                 fmt, args);