Issue #12050: zlib.decompressobj().decompress() now clears the unconsumed_tail

attribute when called without a max_length argument.

1 files changed, 12 insertions, 7 deletions

diff --git a/Modules/zlibmodule.c b/Modules/zlibmodule.c
index 183f01e91a..bd6d6e256b 100644
--- a/Modules/zlibmodule.c
+++ b/Modules/zlibmodule.c
@@ -535,17 +535,22 @@ PyZlib_objdecompress(compobject *self, PyObject *args)
         Py_END_ALLOW_THREADS
     }
 
-    /* Not all of the compressed data could be accommodated in the output buffer
-       of specified size. Return the unconsumed tail in an attribute.*/
     if(max_length) {
+        /* Not all of the compressed data could be accommodated in a buffer of
+           the specified size. Return the unconsumed tail in an attribute. */
         Py_DECREF(self->unconsumed_tail);
         self->unconsumed_tail = PyString_FromStringAndSize((char *)self->zst.next_in,
                                                            self->zst.avail_in);
-        if(!self->unconsumed_tail) {
-            Py_DECREF(RetVal);
-            RetVal = NULL;
-            goto error;
-        }
+    }
+    else if (PyString_GET_SIZE(self->unconsumed_tail) > 0) {
+        /* All of the compressed data was consumed. Clear unconsumed_tail. */
+        Py_DECREF(self->unconsumed_tail);
+        self->unconsumed_tail = PyString_FromStringAndSize("", 0);
+    }
+    if(!self->unconsumed_tail) {
+        Py_DECREF(RetVal);
+        RetVal = NULL;
+        goto error;
     }
 
     /* The end of the compressed data has been reached, so set the