Stackless issue python#70: stackless specific handling of C-return values

If a C-function checks a return value of another C-function of type PyObject*,
it must handle the case of unwinding. This commit fixes PyObject_Call in
abstract.c and simplifies checks in ceval.c.

https://bitbucket.org/stackless-dev/stackless/issues/70

Author: Anselm Kruis

Objects/abstract.c

@@ -2054,14 +2054,14 @@ PyObject_Call(PyObject *func, PyObject *arg, PyObject *kw)
 #endif
         Py_LeaveRecursiveCall();
 #ifdef NDEBUG
-        if (result == NULL && !PyErr_Occurred()) {
+        if (STACKLESS_RETVAL(result) == NULL && !PyErr_Occurred()) {
             PyErr_SetString(
                 PyExc_SystemError,
                 "NULL result without error in PyObject_Call");
         }
 #else
-        assert((result != NULL && !PyErr_Occurred())
-                || (result == NULL && PyErr_Occurred()));
+        assert((STACKLESS_RETVAL(result) != NULL && !PyErr_Occurred())
+                || (STACKLESS_RETVAL(result) == NULL && PyErr_Occurred()));
 #endif
         return result;
     }

Python/ceval.c

@@ -3838,13 +3838,8 @@ PyEval_EvalFrame_value(PyFrameObject *f, int throwflag, PyObject *retval)
     if (why != WHY_RETURN)
         retval = NULL;
 
-#ifdef STACKLESS
     assert((STACKLESS_RETVAL(retval) != NULL && !PyErr_Occurred())
             || (STACKLESS_RETVAL(retval) == NULL && PyErr_Occurred()));
-#else
-    assert((retval != NULL && !PyErr_Occurred())
-            || (retval == NULL && PyErr_Occurred()));
-#endif
 
 fast_yield:
     if (co->co_flags & CO_GENERATOR) {
@@ -4901,13 +4896,8 @@ PyEval_CallObjectWithKeywords(PyObject *func, PyObject *arg, PyObject *kw)
     STACKLESS_ASSERT();
     Py_DECREF(arg);
 
-#ifdef STACKLESS
     assert((STACKLESS_RETVAL(result) != NULL && !PyErr_Occurred())
            || (STACKLESS_RETVAL(result) == NULL && PyErr_Occurred()));
-#else
-    assert((result != NULL && !PyErr_Occurred())
-           || (result == NULL && PyErr_Occurred()));
-#endif
     return result;
 }
 
@@ -5062,13 +5052,8 @@ call_function(PyObject ***pp_stack, int oparg
         READ_TIMESTAMP(*pintr1);
         Py_DECREF(func);
     }
-#ifdef STACKLESS
     assert((STACKLESS_RETVAL(x) != NULL && !PyErr_Occurred())
            || (STACKLESS_RETVAL(x) == NULL && PyErr_Occurred()));
-#else
-    assert((x != NULL && !PyErr_Occurred())
-           || (x == NULL && PyErr_Occurred()));
-#endif
 
     /* Clear the stack of the function object.  Also removes
        the arguments in case they weren't consumed already
@@ -5080,13 +5065,8 @@ call_function(PyObject ***pp_stack, int oparg
         PCALL(PCALL_POP);
     }
 
-#ifdef STACKLESS
     assert((STACKLESS_RETVAL(x) != NULL && !PyErr_Occurred())
            || (STACKLESS_RETVAL(x) == NULL && PyErr_Occurred()));
-#else
-    assert((x != NULL && !PyErr_Occurred())
-           || (x == NULL && PyErr_Occurred()));
-#endif
     return x;
 }
 
@@ -5386,13 +5366,8 @@ ext_do_call(PyObject *func, PyObject ***pp_stack, int flags, int na, int nk)
     Py_XDECREF(callargs);
     Py_XDECREF(kwdict);
     Py_XDECREF(stararg);
-#ifdef STACKLESS
     assert((STACKLESS_RETVAL(result) != NULL && !PyErr_Occurred())
            || (STACKLESS_RETVAL(result) == NULL && PyErr_Occurred()));
-#else
-    assert((result != NULL && !PyErr_Occurred())
-           || (result == NULL && PyErr_Occurred()));
-#endif
     return result;
 }
 

Stackless/core/stackless_impl.h

@@ -554,6 +554,8 @@ PyObject * slp_get_channel_callback(void);
 #define STACKLESS_RETRACT() assert(1)
 #define STACKLESS_ASSERT() assert(1)
 
+#define STACKLESS_RETVAL(obj) (obj)
+
 #define STACKLESS_DECLARE_METHOD(type, meth)
 
 #endif /* STACKLESS */