Implement Py_SET_SIZE for managed objects

Author: msimacek

graalpython/com.oracle.graal.python.cext/src/object.c

@@ -2640,7 +2640,7 @@ void PyTruffle_SET_TYPE(PyObject *a, PyTypeObject *b) {
 }
 void PyTruffle_SET_SIZE(PyVarObject *a, Py_ssize_t b) {
 	if (points_to_py_handle_space(a)) {
-		printf("changing the size of an object is not supported\n");
+		Graal_PyTruffle_SET_SIZE(a, b);
 	} else {
 		a->ob_size = b;
 	}

graalpython/com.oracle.graal.python.test/src/tests/cpyext/test_bytes.py

@@ -517,6 +517,27 @@ class TestPyBytes(CPyExtTestCase):
         cmpfunc=unhandled_error_compare
     )
 
+    test_set_size = CPyExtFunction(
+        lambda args: b'1234',
+        lambda: ((),),
+        code="""
+        PyObject* set_size() {
+            PyObject* output = PyBytes_FromStringAndSize(NULL, 50);
+            if (output == NULL)
+                return NULL;
+            char* s = PyBytes_AsString(output);
+            memcpy(s, "1234", 4);
+            Py_SET_SIZE(output, 4);
+            return output;
+        }
+        """,
+        resultspec="O",
+        argspec="",
+        arguments=[],
+        callfunction="set_size",
+        cmpfunc=unhandled_error_compare
+    )
+
 
 class ObjectTests(unittest.TestCase):
     def test_create_from_buffer(self):

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/modules/cext/PythonCextObjectBuiltins.java

@@ -50,6 +50,7 @@
 import static com.oracle.graal.python.builtins.objects.cext.capi.transitions.ArgDescriptor.PyObjectTransfer;
 import static com.oracle.graal.python.builtins.objects.cext.capi.transitions.ArgDescriptor.PyObjectWrapper;
 import static com.oracle.graal.python.builtins.objects.cext.capi.transitions.ArgDescriptor.PyThreadState;
+import static com.oracle.graal.python.builtins.objects.cext.capi.transitions.ArgDescriptor.PyVarObject;
 import static com.oracle.graal.python.builtins.objects.cext.capi.transitions.ArgDescriptor.Py_hash_t;
 import static com.oracle.graal.python.builtins.objects.cext.capi.transitions.ArgDescriptor.Py_ssize_t;
 import static com.oracle.graal.python.builtins.objects.cext.capi.transitions.ArgDescriptor.VA_LIST_PTR;
@@ -94,6 +95,7 @@
 import com.oracle.graal.python.builtins.objects.cext.common.GetNextVaArgNode;
 import com.oracle.graal.python.builtins.objects.cext.structs.CFields;
 import com.oracle.graal.python.builtins.objects.cext.structs.CStructAccess;
+import com.oracle.graal.python.builtins.objects.common.SequenceNodes;
 import com.oracle.graal.python.builtins.objects.common.SequenceStorageNodes;
 import com.oracle.graal.python.builtins.objects.dict.PDict;
 import com.oracle.graal.python.builtins.objects.function.PKeyword;
@@ -132,6 +134,10 @@
 import com.oracle.graal.python.runtime.PythonOptions;
 import com.oracle.graal.python.runtime.exception.PException;
 import com.oracle.graal.python.runtime.object.PythonObjectFactory;
+import com.oracle.graal.python.runtime.sequence.PSequence;
+import com.oracle.graal.python.runtime.sequence.storage.BasicSequenceStorage;
+import com.oracle.graal.python.runtime.sequence.storage.EmptySequenceStorage;
+import com.oracle.graal.python.runtime.sequence.storage.NativeSequenceStorage;
 import com.oracle.graal.python.runtime.sequence.storage.SequenceStorage;
 import com.oracle.graal.python.util.PythonUtils;
 import com.oracle.truffle.api.CompilerDirectives;
@@ -567,6 +573,29 @@ static PNone doNativeNone() {
         }
     }
 
+    @CApiBuiltin(ret = Void, args = {PyVarObject, Py_ssize_t}, call = Ignored)
+    abstract static class _PyTruffle_SET_SIZE extends CApiBinaryBuiltinNode {
+        @Specialization
+        static PNone set(PSequence obj, long size,
+                        @Bind("this") Node inliningTarget,
+                        @Cached SequenceNodes.GetSequenceStorageNode getSequenceStorageNode) {
+            SequenceStorage storage = getSequenceStorageNode.execute(inliningTarget, obj);
+            // Can't use SetLenNode as that decrefs items for native storages when shrinking
+            if (storage instanceof BasicSequenceStorage basicStorage) {
+                basicStorage.setNewLength((int) size);
+            } else if (storage instanceof NativeSequenceStorage nativeStorage) {
+                nativeStorage.setNewLength((int) size);
+            } else if (storage instanceof EmptySequenceStorage) {
+                if (size > 0) {
+                    throw CompilerDirectives.shouldNotReachHere("invalid Py_SET_SIZE call");
+                }
+            } else {
+                throw CompilerDirectives.shouldNotReachHere("unhandled storage type");
+            }
+            return PNone.NO_VALUE;
+        }
+    }
+
     @CApiBuiltin(ret = Void, args = {PyObjectWrapper}, call = Direct)
     abstract static class _PyObject_Dump extends CApiUnaryBuiltinNode {