[Python-checkins] bpo-34436: Fix check that disables overallocation for the last fmt specifier (GH-8826)

[Miss Islington (bot)]

https://github.com/python/cpython/commit/042082692b7fab7361a8c9d0fb792532bb77e293
commit: 042082692b7fab7361a8c9d0fb792532bb77e293
branch: 3.7
author: Miss Islington (bot) <31488909+miss-islington at users.noreply.github.com>
committer: GitHub <noreply at github.com>
date: 2018-08-23T04:03:02-04:00
summary:

bpo-34436: Fix check that disables overallocation for the last fmt specifier (GH-8826)


Reported by Svace static analyzer.
(cherry picked from commit ccd99752675042bd5f67d332c5b0ed85ba1f2da3)

Co-authored-by: Alexey Izbyshev <izbyshev at ispras.ru>

files:
M Objects/bytesobject.c

diff --git a/Objects/bytesobject.c b/Objects/bytesobject.c
index c358756bfea8..82a75457708b 100644
--- a/Objects/bytesobject.c
+++ b/Objects/bytesobject.c
@@ -819,8 +819,8 @@ _PyBytes_FormatEx(const char *format, Py_ssize_t format_len,
             if (v == NULL)
                 goto error;
 
-            if (fmtcnt < 0) {
-                /* last writer: disable writer overallocation */
+            if (fmtcnt == 0) {
+                /* last write: disable writer overallocation */
                 writer.overallocate = 0;
             }
 
@@ -1048,7 +1048,7 @@ _PyBytes_FormatEx(const char *format, Py_ssize_t format_len,
 
         /* If overallocation was disabled, ensure that it was the last
            write. Otherwise, we missed an optimization */
-        assert(writer.overallocate || fmtcnt < 0 || use_bytearray);
+        assert(writer.overallocate || fmtcnt == 0 || use_bytearray);
     } /* until end */
 
     if (argidx < arglen && !dict) {