Memory leak in Python target fixed (#246)

* memory leak fix

* Update core/lf_token.c

Co-authored-by: Edward A. Lee <eal@eecs.berkeley.edu>

* Update python_port.c

It was incorporated to assist with debugging.

* Update python/lib/python_port.c

Co-authored-by: Edward A. Lee <eal@eecs.berkeley.edu>

* Update python/lib/python_port.c

Co-authored-by: Edward A. Lee <eal@eecs.berkeley.edu>

* Update core/lf_token.c

Co-authored-by: Marten Lohstroh <marten@berkeley.edu>

* Update core/lf_token.c

Co-authored-by: Marten Lohstroh <marten@berkeley.edu>

* Update lf_token.c

* Update python_port.c

* Added back Py_INCREF(val) and define a new destructor for output port

* Add python count decrement to the header file

The function is called by the deserializer during federated execution.

* Fixed SegFault during unfederated execution

This commit fixes segfault for unfederated execution, but leads to memory leak during federated execution.

* Minor cleanup.

---------

Co-authored-by: Edward A. Lee <eal@eecs.berkeley.edu>
Co-authored-by: Marten Lohstroh <marten@berkeley.edu>
Co-authored-by: Peter Donovan <peterdonovan@berkeley.edu>

core/lf_token.c

@@ -130,23 +130,24 @@ lf_token_t* lf_writable_copy(lf_port_base_t* port) {
 
 ////////////////////////////////////////////////////////////////////
 //// Internal functions.
-
 void _lf_free_token_value(lf_token_t* token) {
     if (token->value != NULL) {
         // Count frees to issue a warning if this is never freed.
         _lf_count_payload_allocations--;
         // Free the value field (the payload).
-        // First check whether the value field is garbage collected (e.g. in the
-        // Python target), in which case the payload should not be freed.
-#ifndef _LF_GARBAGE_COLLECTED
         LF_PRINT_DEBUG("_lf_free_token_value: Freeing allocated memory for payload (token value): %p",
-                token->value);
-        if (token->type->destructor == NULL) {
-            free(token->value);
-        } else {
+            token->value);
+        // First check the token's destructor field and invoke it if it is not NULL.
+        if (token->type->destructor != NULL) {
             token->type->destructor(token->value);
         }
+        // If Python Target is not enabled and destructor is NULL
+        // Token values should be freed
+        else {
+#ifndef _PYTHON_TARGET_ENABLED
+            free(token->value);
 #endif
+        }
         token->value = NULL;
     }
 }

python/include/python_port.h

@@ -98,4 +98,5 @@ typedef struct {
     FEDERATED_CAPSULE_EXTENSION
 } generic_port_capsule_struct;
 
+void python_count_decrement(void* py_object);
 #endif

python/lib/python_port.c

@@ -36,9 +36,21 @@ THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #include "python_port.h"
 #include "reactor.h"
+#include "api/api.h"
+#include "api/set.h"
 
 PyTypeObject py_port_capsule_t;
 
+//////////// destructor Function(s) /////////////
+/**
+ * Decrease the reference count of PyObject. When the reference count hits zero,
+ * Python can free its memory.
+ * @param py_object A PyObject with count 1 or greater.
+ */
+void python_count_decrement(void* py_object) {
+    Py_XDECREF((PyObject*)py_object);
+}
+
 //////////// set Function(s) /////////////
 /**
  * Set the value and is_present field of self which is of type
@@ -68,7 +80,7 @@ PyTypeObject py_port_capsule_t;
  * @param args contains:
  *      - val: The value to insert into the port struct.
  */
-PyObject* py_port_set(PyObject *self, PyObject *args) {
+PyObject* py_port_set(PyObject* self, PyObject* args) {
     generic_port_capsule_struct* p = (generic_port_capsule_struct*)self;
     PyObject* val = NULL;
 
@@ -85,13 +97,15 @@ PyObject* py_port_set(PyObject *self, PyObject *args) {
     }
 
     if (val) {
-        LF_PRINT_DEBUG("Setting value %p.", val);
-        Py_XDECREF(port->value);
-        Py_INCREF(val);
-        // Call the core lib API to set the port
-        _LF_SET(port, val);
-
+        LF_PRINT_DEBUG("Setting value %p with reference count %d.", val, (int) Py_REFCNT(val));
+        //Py_INCREF(val);
+        //python_count_decrement(port->value);
+
+        lf_token_t* token = lf_new_token((void*)port, val, 1);
+        lf_set_destructor(port, python_count_decrement);
+        lf_set_token(port, token);
         Py_INCREF(val);
+
         // Also set the values for the port capsule.
         p->value = val;
         p->is_present = true;