Re: question: python gc doesn't collect buffer allocated by read_memory()

[Tom Tromey <tromey@redhat.com>]

>>>>> ">" == HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com> writes:

>> I suspect another objects allocated remain while not collected.

Thanks, you are correct.

I used valgrind --tool=massif to find the problem.

TRY_CATCH clears the cleanup chain, so making a cleanup in a TRY_CATCH
and then trying to run or discard it outside the TRY_CATCH will not
work; instead it leaks the cleanup.

I am checking in the appended patch.  It fixes both leaks.  Verified
with massif.

Tom

2012-03-28  Tom Tromey  <tromey@redhat.com>

	* python/py-inferior.c (infpy_read_memory): Remove cleanups and
	explicitly free 'buffer' on exit paths.  Decref 'membuf_object'
	before returning.

diff --git a/gdb/python/py-inferior.c b/gdb/python/py-inferior.c
index 339a221..06d3272 100644
--- a/gdb/python/py-inferior.c
+++ b/gdb/python/py-inferior.c
@@ -405,8 +405,7 @@ infpy_read_memory (PyObject *self, PyObject *args, PyObject *kw)
   CORE_ADDR addr, length;
   void *buffer = NULL;
   membuf_object *membuf_obj;
-  PyObject *addr_obj, *length_obj;
-  struct cleanup *cleanups;
+  PyObject *addr_obj, *length_obj, *result;
   volatile struct gdb_exception except;
   static char *keywords[] = { "address", "length", NULL };
 
@@ -414,8 +413,6 @@ infpy_read_memory (PyObject *self, PyObject *args, PyObject *kw)
 				     &addr_obj, &length_obj))
     return NULL;
 
-  cleanups = make_cleanup (null_cleanup, NULL);
-
   TRY_CATCH (except, RETURN_MASK_ALL)
     {
       if (!get_addr_from_python (addr_obj, &addr)
@@ -426,39 +423,38 @@ infpy_read_memory (PyObject *self, PyObject *args, PyObject *kw)
 	}
 
       buffer = xmalloc (length);
-      make_cleanup (xfree, buffer);
 
       read_memory (addr, buffer, length);
     }
   if (except.reason < 0)
     {
-      do_cleanups (cleanups);
+      xfree (buffer);
       GDB_PY_HANDLE_EXCEPTION (except);
     }
 
   if (error)
     {
-      do_cleanups (cleanups);
+      xfree (buffer);
       return NULL;
     }
 
   membuf_obj = PyObject_New (membuf_object, &membuf_object_type);
   if (membuf_obj == NULL)
     {
+      xfree (buffer);
       PyErr_SetString (PyExc_MemoryError,
 		       _("Could not allocate memory buffer object."));
-      do_cleanups (cleanups);
       return NULL;
     }
 
-  discard_cleanups (cleanups);
-
   membuf_obj->buffer = buffer;
   membuf_obj->addr = addr;
   membuf_obj->length = length;
 
-  return PyBuffer_FromReadWriteObject ((PyObject *) membuf_obj, 0,
-				       Py_END_OF_BUFFER);
+  result = PyBuffer_FromReadWriteObject ((PyObject *) membuf_obj, 0,
+					 Py_END_OF_BUFFER);
+  Py_DECREF (membuf_obj);
+  return result;
 }
 
 /* Implementation of gdb.write_memory (address, buffer [, length]).