Revert "Fix Python reference counting for declared_transform product store caching (#313)"

This reverts commit e348b4d.

Author: knoepfel

plugins/python/src/lifelinewrap.cpp

@@ -9,7 +9,7 @@ static py_lifeline_t* ll_new(PyTypeObject* pytype, PyObject*, PyObject*)
 {
   py_lifeline_t* pyobj = (py_lifeline_t*)pytype->tp_alloc(pytype, 0);
   if (!pyobj)
-    return nullptr;
+    PyErr_Print();
   pyobj->m_view = nullptr;
   new (&pyobj->m_source) std::shared_ptr<void>{};
 

plugins/python/src/modulewrap.cpp

@@ -107,10 +107,6 @@ namespace {
 
       PyGILRAII gil;
 
-      // Args are borrowed references from the product store cache.
-      // XINCREF to create temporary owned references for the duration of the call.
-      (Py_XINCREF((PyObject*)args), ...);
-
       PyObject* result =
         PyObject_CallFunctionObjArgs(m_callable, lifeline_transform(args)..., nullptr);
 
@@ -120,8 +116,7 @@ namespace {
           error_msg = "Unknown python error";
       }
 
-      // Release our temporary references; the cache's references remain intact.
-      (Py_XDECREF((PyObject*)args), ...);
+      decref_all(args...);
 
       if (!error_msg.empty()) {
         throw std::runtime_error(error_msg.c_str());
@@ -137,12 +132,7 @@ namespace {
 
       PyGILRAII gil;
 
-      // Args are borrowed references from the product store cache.
-      // XINCREF to create temporary owned references for the duration of the call.
-      (Py_XINCREF((PyObject*)args), ...);
-
-      PyObject* result =
-        PyObject_CallFunctionObjArgs(m_callable, lifeline_transform(args)..., nullptr);
+      PyObject* result = PyObject_CallFunctionObjArgs(m_callable, (PyObject*)args..., nullptr);
 
       std::string error_msg;
       if (!result) {
@@ -151,13 +141,20 @@ namespace {
       } else
         Py_DECREF(result);
 
-      // Release our temporary references; the cache's references remain intact.
-      (Py_XDECREF((PyObject*)args), ...);
+      decref_all(args...);
 
       if (!error_msg.empty()) {
         throw std::runtime_error(error_msg.c_str());
       }
     }
+
+  private:
+    template <typename... Args>
+    void decref_all(Args... args)
+    {
+      // helper to decrement reference counts of N arguments
+      (Py_DECREF((PyObject*)args), ...);
+    }
   };
 
   // use explicit instatiations to ensure that the function signature can
@@ -336,13 +333,14 @@ namespace {
                                                                                                    \
   static cpptype py_to_##name(intptr_t pyobj)                                                      \
   {                                                                                                \
-    /* Input is a borrowed reference from the product store cache — do not DECREF. */              \
     PyGILRAII gil;                                                                                 \
     cpptype i = (cpptype)frompy((PyObject*)pyobj);                                                 \
     std::string msg;                                                                               \
     if (msg_from_py_error(msg, true)) {                                                            \
+      Py_DECREF((PyObject*)pyobj);                                                                 \
       throw std::runtime_error("Python conversion error for type " #name ": " + msg);              \
     }                                                                                              \
+    Py_DECREF((PyObject*)pyobj);                                                                   \
     return i;                                                                                      \
   }
 
@@ -360,7 +358,7 @@ namespace {
     PyGILRAII gil;                                                                                 \
                                                                                                    \
     if (!v)                                                                                        \
-      throw std::runtime_error("null vector<" #cpptype "> passed to " #name "_to_py");             \
+      return (intptr_t)nullptr;                                                                    \
                                                                                                    \
     /* use a numpy view with the shared pointer tied up in a lifeline object (note: this */        \
     /* is just a demonstrator; alternatives are still being considered) */                         \
@@ -373,7 +371,7 @@ namespace {
     );                                                                                             \
                                                                                                    \
     if (!np_view)                                                                                  \
-      throw std::runtime_error("failed to create numpy array in " #name "_to_py");                 \
+      return (intptr_t)nullptr;                                                                    \
                                                                                                    \
     /* make the data read-only by not making it writable */                                        \
     PyArray_CLEARFLAGS((PyArrayObject*)np_view, NPY_ARRAY_WRITEABLE);                              \
@@ -385,7 +383,7 @@ namespace {
       (py_lifeline_t*)PhlexLifeline_Type.tp_new(&PhlexLifeline_Type, nullptr, nullptr);            \
     if (!pyll) {                                                                                   \
       Py_DECREF(np_view);                                                                          \
-      throw std::runtime_error("failed to create lifeline in " #name "_to_py");                    \
+      return (intptr_t)nullptr;                                                                    \
     }                                                                                              \
     pyll->m_source = v;                                                                            \
     pyll->m_view = np_view; /* steals reference */                                                 \
@@ -403,7 +401,6 @@ namespace {
 #define NUMPY_ARRAY_CONVERTER(name, cpptype, nptype, frompy)                                       \
   static std::shared_ptr<std::vector<cpptype>> py_to_##name(intptr_t pyobj)                        \
   {                                                                                                \
-    /* Input is a borrowed reference from the product store cache — do not DECREF. */              \
     PyGILRAII gil;                                                                                 \
                                                                                                    \
     auto vec = std::make_shared<std::vector<cpptype>>();                                           \
@@ -441,6 +438,7 @@ namespace {
       }                                                                                            \
     }                                                                                              \
                                                                                                    \
+    Py_DECREF((PyObject*)pyobj);                                                                   \
     return vec;                                                                                    \
   }