at least on cpython 3.4, the PyBytes_Len and PyBytes_AsString functions are forgiving and deal with unicode objects, too

Author: timfel

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/modules/TruffleCextBuiltins.java

@@ -957,14 +957,23 @@ Object doUnicode(String s, long elementSize, long elements, Object errorMarker)
     @GenerateNodeFactory
     abstract static class PyTruffle_Bytes_AsString extends NativeBuiltin {
         @Specialization
-        Object doUnicode(PBytes bytes, @SuppressWarnings("unused") Object errorMarker) {
+        Object doBytes(PBytes bytes, @SuppressWarnings("unused") Object errorMarker) {
             // according to Python's documentation, the last byte is always '0x00'
             byte[] store = bytes.getInternalByteArray();
             byte[] nativeBytes = Arrays.copyOf(store, store.length + 1);
             assert nativeBytes[nativeBytes.length - 1] == 0;
             return getContext().getEnv().asGuestValue(nativeBytes);
         }
 
+        @Specialization
+        Object doUnicode(PString str, @SuppressWarnings("unused") Object errorMarker) {
+            // according to Python's documentation, the last byte is always '0x00'
+            byte[] store = str.getValue().getBytes();
+            byte[] nativeBytes = Arrays.copyOf(store, store.length + 1);
+            assert nativeBytes[nativeBytes.length - 1] == 0;
+            return getContext().getEnv().asGuestValue(nativeBytes);
+        }
+
         @Fallback
         Object doUnicode(@SuppressWarnings("unused") Object o, Object errorMarker) {
             return errorMarker;

graalpython/lib-graalpython/python_cext.py

@@ -193,7 +193,6 @@ def PyBytes_AsStringCheckEmbeddedNull(obj, encoding):
 
 
 def PyBytes_Size(obj):
-    assert isinstance(obj, bytes)
     return PyObject_Size(obj)