To augment the various PyObject_CallMethod...() functions, we add _PyObject_VectorcallMethod() which uses the vectorcall calling convention. To be consistent with the other vectorcall functions, this function is provisional for now.

For efficiency, the "self" argument is NOT passed as separate argument but as part of the usual args array. In other words, the call looks like an unbound method call.

I am also adding _PyObject_VectorcallMethodId() taking a _Py_Identifier* as argument and convenience functions PyObject_CallMethodNoArgs() and _PyObject_CallMethodIdNoArgs(), analogous to the recently added PyObject_CallNoArgs().

New changeset b1263d5a60d3f7ab02dd28409fff59b3815a3f67 by Inada Naoki (Jeroen Demeyer) in branch 'master':
bpo-37337: Add _PyObject_VectorcallMethod() (GH-14228)
https://github.com/python/cpython/commit/b1263d5a60d3f7ab02dd28409fff59b3815a3f67

New changeset 762f93ff2efd6b7ef0177cad57939c0ab2002eac by Inada Naoki (Jeroen Demeyer) in branch 'master':
bpo-37337: Add _PyObject_CallMethodNoArgs() (GH-14267)
https://github.com/python/cpython/commit/762f93ff2efd6b7ef0177cad57939c0ab2002eac

Thank you, Jeroen and INADA-san!

Commit b1263d5a60d3f7ab02dd28409fff59b3815a3f67 causes GCC 9.1.0 to give a warning in Objects/descrobject.c.

Objects/descrobject.c:1050:19: warning: cast between incompatible function types from ‘PyObject * (*)(mappingproxyobject *, PyObject * const*, Py_ssize_t)’ {aka ‘struct _object * (*)(struct <anonymous> *, struct _object * const*, long int)’} to ‘PyObject * (*)(PyObject *, PyObject *)’ {aka ‘struct _object * (*)(struct _object *, struct _object *)’} [-Wcast-function-type]
 1050 |     {"get",       (PyCFunction)mappingproxy_get,        METH_FASTCALL,
      |                   ^

PR 14814 fixes this.

New changeset 43d564c18c97421f73025ac3132a194975c76bd6 by Inada Naoki (Zackery Spytz) in branch 'master':
bpo-37337: Fix a GCC 9 warning in Objects/descrobject.c (GH-14814)
https://github.com/python/cpython/commit/43d564c18c97421f73025ac3132a194975c76bd6