[Bug #1083110] calling .flush() on decompress objects causes a segfault due to an uninitialized pointer: fixes the problem and adds a test case

Lib/test/test_zlib.py

@@ -290,6 +290,16 @@ class CompressObjectTestCase(unittest.TestCase):
             # if decompressed data is different from the input data, choke.
             self.assertEqual(expanded, data, "17K random source doesn't match")
 
+    def test_empty_flush(self):
+        # Test that calling .flush() on unused objects works.
+        # (Bug #1083110 -- calling .flush() on decompress objects
+        # caused a core dump.)
+
+        co = zlib.compressobj(zlib.Z_BEST_COMPRESSION)
+        self.failUnless(co.flush())  # Returns a zlib header
+        dco = zlib.decompressobj()
+        self.assertEqual(dco.flush(), "") # Returns nothing
+        
 
 def genblock(seed, length, step=1024, generator=random):
     """length-byte stream of random data from a seed (in step-byte blocks)."""

Misc/NEWS

@@ -64,6 +64,9 @@ Library
   once when a size argument is given. This prevents a buffer overflow in the
   tokenizer with very long source lines.
 
+- Bug #1083110: ``zlib.decompress.flush()`` would segfault if called immediately
+  after creating the object, without any intervening ``.decompress()`` calls.
+
 
 Build
 -----

Modules/zlibmodule.c

@@ -301,6 +301,8 @@ PyZlib_compressobj(PyObject *selfptr, PyObject *args)
 	return(NULL);
     self->zst.zalloc = (alloc_func)NULL;
     self->zst.zfree = (free_func)Z_NULL;
+    self->zst.next_in = NULL;
+    self->zst.avail_in = 0;
     err = deflateInit2(&self->zst, level, method, wbits, memLevel, strategy);
     switch(err) {
     case (Z_OK):
@@ -335,6 +337,8 @@ PyZlib_decompressobj(PyObject *selfptr, PyObject *args)
 	return(NULL);
     self->zst.zalloc = (alloc_func)NULL;
     self->zst.zfree = (free_func)Z_NULL;
+    self->zst.next_in = NULL;
+    self->zst.avail_in = 0;
     err = inflateInit2(&self->zst, wbits);
     switch(err) {
     case (Z_OK):
@@ -516,7 +520,7 @@ PyZlib_objdecompress(compobject *self, PyObject *args)
 	Py_END_ALLOW_THREADS
     }
 
-    /* Not all of the compressed data could be accomodated in the output buffer
+    /* 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) {
 	Py_DECREF(self->unconsumed_tail);