From fbbf5f307a60a88be0a7b13d9f8ef6374b409566 Mon Sep 17 00:00:00 2001
From: "Erlend E. Aasland" <erlend@python.org>
Date: Wed, 10 Apr 2024 20:58:36 +0200
Subject: [PATCH 01/17] PoC: str vectorcall

---
 Objects/unicodeobject.c | 129 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 129 insertions(+)

diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 5f15071d7d54ef..0211ab49bc56dc 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -14617,6 +14617,134 @@ unicode_new_impl(PyTypeObject *type, PyObject *x, const char *encoding,
     return unicode;
 }
 
+static const char *
+as_const_char(PyObject *obj)
+{
+    if (!PyUnicode_Check(obj)) {
+        _PyArg_BadArgument("str", "argument", "str", obj);
+        return NULL;
+    }
+    Py_ssize_t sz;
+    const char *str = PyUnicode_AsUTF8AndSize(obj, &sz);
+    if (str == NULL) {
+        return NULL;
+    }
+    if (strlen(str) != (size_t)sz) {
+        PyErr_SetString(PyExc_ValueError, "embedded null character");
+        return NULL;
+    }
+    return str;
+}
+
+static PyObject *
+fallback_to_tp_call(PyObject *type, Py_ssize_t nargs, Py_ssize_t nkwargs,
+                    PyObject *const *args, PyObject *kwnames)
+{
+    PyObject *tuple = PyTuple_New(nargs);
+    if (tuple == NULL) {
+        return NULL;
+    }
+    for (Py_ssize_t i = 0; i < nargs; i++) {
+        PyObject *value = Py_NewRef(args[i]);
+        PyTuple_SET_ITEM(tuple, i, value);
+    }
+    PyObject *dict = PyDict_New();
+    if (dict == NULL) {
+        Py_DECREF(tuple);
+        return NULL;
+    }
+    for (Py_ssize_t j = 0; j < nkwargs; j++) {
+        PyObject *key = PyTuple_GET_ITEM(kwnames, j);
+        PyObject *value = args[nargs + j];
+        if (PyDict_SetItem(dict, key, value) < 0) {
+            Py_DECREF(tuple);
+            Py_DECREF(dict);
+            return NULL;
+        }
+    }
+    return unicode_new(_PyType_CAST(type), tuple, dict);
+}
+
+static PyObject *
+unicode_vectorcall(PyObject *type, PyObject *const *args,
+                   size_t nargsf, PyObject *kwnames)
+{
+    Py_ssize_t nargs = PyVectorcall_NARGS(nargsf);
+    Py_ssize_t nkwargs = (kwnames) ? PyTuple_GET_SIZE(kwnames) : 0;
+    if (nargs == 0 && nkwargs == 0) {
+        return unicode_get_empty();
+    }
+    PyObject *object = args[0];
+    if (nargs == 1 && nkwargs == 0) {
+        return unicode_new_impl(_PyType_CAST(type), object, NULL, NULL);
+    }
+    if (nargs + nkwargs == 2) {
+        const char *encoding;
+        const char *errors;
+        if (nkwargs == 1) {
+            PyObject *kw0 = PyTuple_GET_ITEM(kwnames, 0);
+            if (_PyUnicode_EqualToASCIIString(kw0, "encoding")) {
+                encoding = as_const_char(args[1]);
+                if (encoding == NULL) {
+                    return NULL;
+                }
+                errors = NULL;
+            }
+            else if (_PyUnicode_EqualToASCIIString(kw0, "errors")) {
+                errors = as_const_char(args[1]);
+                if (errors == NULL) {
+                    return NULL;
+                }
+                encoding = NULL;
+            }
+            else {
+                PyErr_Format(PyExc_TypeError,
+                    "'%S' is an invalid keyword argument for str()", kw0);
+                return NULL;
+            }
+        }
+        else if (nkwargs == 0) {
+            encoding = as_const_char(args[1]);
+            errors = NULL;
+        }
+        else {
+            return fallback_to_tp_call(type, nargs, nkwargs, args, kwnames);
+        }
+        PyObject *object = args[0];
+        return unicode_new_impl(_PyType_CAST(type), object, encoding, errors);
+    }
+    if (nargs + nkwargs == 3) {
+        if (nkwargs == 1) {
+            PyObject *kw0 = PyTuple_GET_ITEM(kwnames, 0);
+            if (!_PyUnicode_EqualToASCIIString(kw0, "errors")) {
+                PyErr_Format(PyExc_TypeError,
+                    "'%S' is an invalid keyword argument for str()", kw0);
+                return NULL;
+            }
+        }
+        else if (nkwargs != 0) {
+            return fallback_to_tp_call(type, nargs, nkwargs, args, kwnames);
+        }
+        PyObject *object = args[0];
+        const char *encoding = as_const_char(args[1]);
+        if (encoding == NULL) {
+            return NULL;
+        }
+        const char *errors = as_const_char(args[2]);
+        if (errors == NULL) {
+            return NULL;
+        }
+        return unicode_new_impl(_PyType_CAST(type), object, encoding, errors);
+    }
+    if (nargs > 3) {
+        PyErr_Format(PyExc_TypeError,
+            "str() takes at most 3 arguments (%d given)", nargs + nkwargs);
+        return NULL;
+    }
+
+    return fallback_to_tp_call(type, nargs, nkwargs, args, kwnames);
+}
+
 static PyObject *
 unicode_subtype_new(PyTypeObject *type, PyObject *unicode)
 {
@@ -14758,6 +14886,7 @@ PyTypeObject PyUnicode_Type = {
     0,                            /* tp_alloc */
     unicode_new,                  /* tp_new */
     PyObject_Del,                 /* tp_free */
+    .tp_vectorcall = unicode_vectorcall,
 };
 
 /* Initialize the Unicode implementation */

From 2a94bfa7da458364a4dee2a6a6c1a695aa9cee26 Mon Sep 17 00:00:00 2001
From: "Erlend E. Aasland" <erlend@python.org>
Date: Wed, 10 Apr 2024 22:15:01 +0200
Subject: [PATCH 02/17] Nicer error message

---
 Objects/unicodeobject.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 0211ab49bc56dc..aac8bfed672db6 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -14618,10 +14618,12 @@ unicode_new_impl(PyTypeObject *type, PyObject *x, const char *encoding,
 }
 
 static const char *
-as_const_char(PyObject *obj)
+as_const_char(PyObject *obj, const char *name)
 {
     if (!PyUnicode_Check(obj)) {
-        _PyArg_BadArgument("str", "argument", "str", obj);
+        PyErr_Format(PyExc_TypeError,
+                     "str() argument '%s' must be str, not %T",
+                     name, obj);
         return NULL;
     }
     Py_ssize_t sz;
@@ -14684,14 +14686,14 @@ unicode_vectorcall(PyObject *type, PyObject *const *args,
         if (nkwargs == 1) {
             PyObject *kw0 = PyTuple_GET_ITEM(kwnames, 0);
             if (_PyUnicode_EqualToASCIIString(kw0, "encoding")) {
-                encoding = as_const_char(args[1]);
+                encoding = as_const_char(args[1], "encoding");
                 if (encoding == NULL) {
                     return NULL;
                 }
                 errors = NULL;
             }
             else if (_PyUnicode_EqualToASCIIString(kw0, "errors")) {
-                errors = as_const_char(args[1]);
+                errors = as_const_char(args[1], "errors");
                 if (errors == NULL) {
                     return NULL;
                 }
@@ -14704,7 +14706,7 @@ unicode_vectorcall(PyObject *type, PyObject *const *args,
             }
         }
         else if (nkwargs == 0) {
-            encoding = as_const_char(args[1]);
+            encoding = as_const_char(args[1], "encoding");
             errors = NULL;
         }
         else {
@@ -14726,11 +14728,11 @@ unicode_vectorcall(PyObject *type, PyObject *const *args,
             return fallback_to_tp_call(type, nargs, nkwargs, args, kwnames);
         }
         PyObject *object = args[0];
-        const char *encoding = as_const_char(args[1]);
+        const char *encoding = as_const_char(args[1], "encoding");
         if (encoding == NULL) {
             return NULL;
         }
-        const char *errors = as_const_char(args[2]);
+        const char *errors = as_const_char(args[2], "errors");
         if (errors == NULL) {
             return NULL;
         }

From 1a29140ddb0ae26a8e79fe6bb700de7aaf243bb1 Mon Sep 17 00:00:00 2001
From: "Erlend E. Aasland" <erlend@python.org>
Date: Wed, 10 Apr 2024 22:16:27 +0200
Subject: [PATCH 03/17] NEWS

---
 .../2024-04-10-22-16-18.gh-issue-117709.-_1YL0.rst              | 2 ++
 1 file changed, 2 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Core and Builtins/2024-04-10-22-16-18.gh-issue-117709.-_1YL0.rst

diff --git a/Misc/NEWS.d/next/Core and Builtins/2024-04-10-22-16-18.gh-issue-117709.-_1YL0.rst b/Misc/NEWS.d/next/Core and Builtins/2024-04-10-22-16-18.gh-issue-117709.-_1YL0.rst
new file mode 100644
index 00000000000000..1877ac5818cb69
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2024-04-10-22-16-18.gh-issue-117709.-_1YL0.rst	
@@ -0,0 +1,2 @@
+Speed up calls to :func:`str` by using the :pep:`590` ``vectorcall`` calling
+convention. Patch by Erlend Aasland.

From 311aa3cdca0199b620447425fda90e47feaf16dd Mon Sep 17 00:00:00 2001
From: "Erlend E. Aasland" <erlend@python.org>
Date: Wed, 10 Apr 2024 22:44:03 +0200
Subject: [PATCH 04/17] Don't call unicode_get_empty() directly; remove some
 unneeded assignments

---
 Objects/unicodeobject.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index aac8bfed672db6..01111c47b01abc 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -14674,7 +14674,7 @@ unicode_vectorcall(PyObject *type, PyObject *const *args,
     Py_ssize_t nargs = PyVectorcall_NARGS(nargsf);
     Py_ssize_t nkwargs = (kwnames) ? PyTuple_GET_SIZE(kwnames) : 0;
     if (nargs == 0 && nkwargs == 0) {
-        return unicode_get_empty();
+        return unicode_new_impl(_PyType_CAST(type), NULL, NULL, NULL);
     }
     PyObject *object = args[0];
     if (nargs == 1 && nkwargs == 0) {
@@ -14712,7 +14712,6 @@ unicode_vectorcall(PyObject *type, PyObject *const *args,
         else {
             return fallback_to_tp_call(type, nargs, nkwargs, args, kwnames);
         }
-        PyObject *object = args[0];
         return unicode_new_impl(_PyType_CAST(type), object, encoding, errors);
     }
     if (nargs + nkwargs == 3) {
@@ -14727,7 +14726,6 @@ unicode_vectorcall(PyObject *type, PyObject *const *args,
         else if (nkwargs != 0) {
             return fallback_to_tp_call(type, nargs, nkwargs, args, kwnames);
         }
-        PyObject *object = args[0];
         const char *encoding = as_const_char(args[1], "encoding");
         if (encoding == NULL) {
             return NULL;

From c59478c0e32c51b7ae0b6743a6aff13a57fa5e2a Mon Sep 17 00:00:00 2001
From: "Erlend E. Aasland" <erlend@python.org>
Date: Wed, 10 Apr 2024 23:01:52 +0200
Subject: [PATCH 05/17] type is always PyUnicode_Type?

---
 Objects/unicodeobject.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 01111c47b01abc..f6d1c46ac799cd 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -14671,14 +14671,16 @@ static PyObject *
 unicode_vectorcall(PyObject *type, PyObject *const *args,
                    size_t nargsf, PyObject *kwnames)
 {
+    assert(Py_Is(_PyType_CAST(type), &PyUnicode_Type));
+
     Py_ssize_t nargs = PyVectorcall_NARGS(nargsf);
     Py_ssize_t nkwargs = (kwnames) ? PyTuple_GET_SIZE(kwnames) : 0;
     if (nargs == 0 && nkwargs == 0) {
-        return unicode_new_impl(_PyType_CAST(type), NULL, NULL, NULL);
+        return unicode_get_empty();
     }
     PyObject *object = args[0];
     if (nargs == 1 && nkwargs == 0) {
-        return unicode_new_impl(_PyType_CAST(type), object, NULL, NULL);
+        return PyObject_Str(object);
     }
     if (nargs + nkwargs == 2) {
         const char *encoding;
@@ -14712,7 +14714,7 @@ unicode_vectorcall(PyObject *type, PyObject *const *args,
         else {
             return fallback_to_tp_call(type, nargs, nkwargs, args, kwnames);
         }
-        return unicode_new_impl(_PyType_CAST(type), object, encoding, errors);
+        return PyUnicode_FromEncodedObject(object, encoding, errors);
     }
     if (nargs + nkwargs == 3) {
         if (nkwargs == 1) {
@@ -14734,7 +14736,7 @@ unicode_vectorcall(PyObject *type, PyObject *const *args,
         if (errors == NULL) {
             return NULL;
         }
-        return unicode_new_impl(_PyType_CAST(type), object, encoding, errors);
+        return PyUnicode_FromEncodedObject(object, encoding, errors);
     }
     if (nargs > 3) {
         PyErr_Format(PyExc_TypeError,

From 068de64f5343e222f73bfc8ef4c1b0e863cb8414 Mon Sep 17 00:00:00 2001
From: "Erlend E. Aasland" <erlend@python.org>
Date: Thu, 11 Apr 2024 10:08:08 +0200
Subject: [PATCH 06/17] Address review: variable naming

---
 Objects/unicodeobject.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index f6d1c46ac799cd..9d8838eb5f6d9f 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -14686,15 +14686,15 @@ unicode_vectorcall(PyObject *type, PyObject *const *args,
         const char *encoding;
         const char *errors;
         if (nkwargs == 1) {
-            PyObject *kw0 = PyTuple_GET_ITEM(kwnames, 0);
-            if (_PyUnicode_EqualToASCIIString(kw0, "encoding")) {
+            PyObject *key = PyTuple_GET_ITEM(kwnames, 0);
+            if (_PyUnicode_EqualToASCIIString(key, "encoding")) {
                 encoding = as_const_char(args[1], "encoding");
                 if (encoding == NULL) {
                     return NULL;
                 }
                 errors = NULL;
             }
-            else if (_PyUnicode_EqualToASCIIString(kw0, "errors")) {
+            else if (_PyUnicode_EqualToASCIIString(key, "errors")) {
                 errors = as_const_char(args[1], "errors");
                 if (errors == NULL) {
                     return NULL;
@@ -14703,7 +14703,7 @@ unicode_vectorcall(PyObject *type, PyObject *const *args,
             }
             else {
                 PyErr_Format(PyExc_TypeError,
-                    "'%S' is an invalid keyword argument for str()", kw0);
+                    "'%S' is an invalid keyword argument for str()", key);
                 return NULL;
             }
         }
@@ -14718,10 +14718,10 @@ unicode_vectorcall(PyObject *type, PyObject *const *args,
     }
     if (nargs + nkwargs == 3) {
         if (nkwargs == 1) {
-            PyObject *kw0 = PyTuple_GET_ITEM(kwnames, 0);
-            if (!_PyUnicode_EqualToASCIIString(kw0, "errors")) {
+            PyObject *key = PyTuple_GET_ITEM(kwnames, 0);
+            if (!_PyUnicode_EqualToASCIIString(key, "errors")) {
                 PyErr_Format(PyExc_TypeError,
-                    "'%S' is an invalid keyword argument for str()", kw0);
+                    "'%S' is an invalid keyword argument for str()", key);
                 return NULL;
             }
         }

From 57c01a4f57e79407058dad119d7a2159cff3b507 Mon Sep 17 00:00:00 2001
From: "Erlend E. Aasland" <erlend@python.org>
Date: Thu, 11 Apr 2024 10:09:27 +0200
Subject: [PATCH 07/17] Align exception messages with tp_call

---
 Objects/unicodeobject.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 9d8838eb5f6d9f..dc3934233f1542 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -14703,7 +14703,7 @@ unicode_vectorcall(PyObject *type, PyObject *const *args,
             }
             else {
                 PyErr_Format(PyExc_TypeError,
-                    "'%S' is an invalid keyword argument for str()", key);
+                    "str() got an unexpected keyword argument %R", key);
                 return NULL;
             }
         }
@@ -14721,7 +14721,7 @@ unicode_vectorcall(PyObject *type, PyObject *const *args,
             PyObject *key = PyTuple_GET_ITEM(kwnames, 0);
             if (!_PyUnicode_EqualToASCIIString(key, "errors")) {
                 PyErr_Format(PyExc_TypeError,
-                    "'%S' is an invalid keyword argument for str()", key);
+                    "str() got an unexpected keyword argument %R", key);
                 return NULL;
             }
         }

From 37b45ed8c5e69a97b911db20adaca46474646413 Mon Sep 17 00:00:00 2001
From: "Erlend E. Aasland" <erlend@python.org>
Date: Thu, 11 Apr 2024 10:13:39 +0200
Subject: [PATCH 08/17] Address review: use better internal APIs

---
 Objects/unicodeobject.c | 24 +++---------------------
 1 file changed, 3 insertions(+), 21 deletions(-)

diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index dc3934233f1542..5de4e0e8fa560e 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -14626,15 +14626,10 @@ as_const_char(PyObject *obj, const char *name)
                      name, obj);
         return NULL;
     }
-    Py_ssize_t sz;
-    const char *str = PyUnicode_AsUTF8AndSize(obj, &sz);
+    const char *str = _PyUnicode_AsUTF8NoNUL(obj);
     if (str == NULL) {
         return NULL;
     }
-    if (strlen(str) != (size_t)sz) {
-        PyErr_SetString(PyExc_ValueError, "embedded null character");
-        return NULL;
-    }
     return str;
 }
 
@@ -14642,28 +14637,15 @@ static PyObject *
 fallback_to_tp_call(PyObject *type, Py_ssize_t nargs, Py_ssize_t nkwargs,
                     PyObject *const *args, PyObject *kwnames)
 {
-    PyObject *tuple = PyTuple_New(nargs);
+    PyObject *tuple = _PyTuple_FromArray(args, nargs);
     if (tuple == NULL) {
         return NULL;
     }
-    for (Py_ssize_t i = 0; i < nargs; i++) {
-        PyObject *value = Py_NewRef(args[i]);
-        PyTuple_SET_ITEM(tuple, i, value);
-    }
-    PyObject *dict = PyDict_New();
+    PyObject *dict = _PyStack_AsDict(args + nargs, kwnames);
     if (dict == NULL) {
         Py_DECREF(tuple);
         return NULL;
     }
-    for (Py_ssize_t j = 0; j < nkwargs; j++) {
-        PyObject *key = PyTuple_GET_ITEM(kwnames, j);
-        PyObject *value = args[nargs + j];
-        if (PyDict_SetItem(dict, key, value) < 0) {
-            Py_DECREF(tuple);
-            Py_DECREF(dict);
-            return NULL;
-        }
-    }
     return unicode_new(_PyType_CAST(type), tuple, dict);
 }
 

From 7e141e792b5f733e4636958f5e5ef289c6a770e9 Mon Sep 17 00:00:00 2001
From: "Erlend E. Aasland" <erlend@python.org>
Date: Thu, 11 Apr 2024 10:14:47 +0200
Subject: [PATCH 09/17] Address review: explcitly initialise variables

---
 Objects/unicodeobject.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 5de4e0e8fa560e..2a6f05d59baecd 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -14665,8 +14665,8 @@ unicode_vectorcall(PyObject *type, PyObject *const *args,
         return PyObject_Str(object);
     }
     if (nargs + nkwargs == 2) {
-        const char *encoding;
-        const char *errors;
+        const char *encoding = NULL;
+        const char *errors = NULL;
         if (nkwargs == 1) {
             PyObject *key = PyTuple_GET_ITEM(kwnames, 0);
             if (_PyUnicode_EqualToASCIIString(key, "encoding")) {
@@ -14674,14 +14674,12 @@ unicode_vectorcall(PyObject *type, PyObject *const *args,
                 if (encoding == NULL) {
                     return NULL;
                 }
-                errors = NULL;
             }
             else if (_PyUnicode_EqualToASCIIString(key, "errors")) {
                 errors = as_const_char(args[1], "errors");
                 if (errors == NULL) {
                     return NULL;
                 }
-                encoding = NULL;
             }
             else {
                 PyErr_Format(PyExc_TypeError,
@@ -14691,7 +14689,6 @@ unicode_vectorcall(PyObject *type, PyObject *const *args,
         }
         else if (nkwargs == 0) {
             encoding = as_const_char(args[1], "encoding");
-            errors = NULL;
         }
         else {
             return fallback_to_tp_call(type, nargs, nkwargs, args, kwnames);

From b09a3fa1d22fb382afbe42c48448629223f886c3 Mon Sep 17 00:00:00 2001
From: "Erlend E. Aasland" <erlend@python.org>
Date: Thu, 11 Apr 2024 10:28:16 +0200
Subject: [PATCH 10/17] Only optimise for positional-only arguments

---
 Objects/unicodeobject.c | 98 +++++++++++------------------------------
 1 file changed, 25 insertions(+), 73 deletions(-)

diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 2a6f05d59baecd..307c0b30e57538 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -14633,22 +14633,6 @@ as_const_char(PyObject *obj, const char *name)
     return str;
 }
 
-static PyObject *
-fallback_to_tp_call(PyObject *type, Py_ssize_t nargs, Py_ssize_t nkwargs,
-                    PyObject *const *args, PyObject *kwnames)
-{
-    PyObject *tuple = _PyTuple_FromArray(args, nargs);
-    if (tuple == NULL) {
-        return NULL;
-    }
-    PyObject *dict = _PyStack_AsDict(args + nargs, kwnames);
-    if (dict == NULL) {
-        Py_DECREF(tuple);
-        return NULL;
-    }
-    return unicode_new(_PyType_CAST(type), tuple, dict);
-}
-
 static PyObject *
 unicode_vectorcall(PyObject *type, PyObject *const *args,
                    size_t nargsf, PyObject *kwnames)
@@ -14657,73 +14641,41 @@ unicode_vectorcall(PyObject *type, PyObject *const *args,
 
     Py_ssize_t nargs = PyVectorcall_NARGS(nargsf);
     Py_ssize_t nkwargs = (kwnames) ? PyTuple_GET_SIZE(kwnames) : 0;
-    if (nargs == 0 && nkwargs == 0) {
-        return unicode_get_empty();
-    }
-    PyObject *object = args[0];
-    if (nargs == 1 && nkwargs == 0) {
-        return PyObject_Str(object);
-    }
-    if (nargs + nkwargs == 2) {
-        const char *encoding = NULL;
-        const char *errors = NULL;
-        if (nkwargs == 1) {
-            PyObject *key = PyTuple_GET_ITEM(kwnames, 0);
-            if (_PyUnicode_EqualToASCIIString(key, "encoding")) {
-                encoding = as_const_char(args[1], "encoding");
-                if (encoding == NULL) {
-                    return NULL;
-                }
-            }
-            else if (_PyUnicode_EqualToASCIIString(key, "errors")) {
-                errors = as_const_char(args[1], "errors");
-                if (errors == NULL) {
-                    return NULL;
-                }
-            }
-            else {
-                PyErr_Format(PyExc_TypeError,
-                    "str() got an unexpected keyword argument %R", key);
-                return NULL;
-            }
-        }
-        else if (nkwargs == 0) {
-            encoding = as_const_char(args[1], "encoding");
-        }
-        else {
-            return fallback_to_tp_call(type, nargs, nkwargs, args, kwnames);
-        }
-        return PyUnicode_FromEncodedObject(object, encoding, errors);
-    }
-    if (nargs + nkwargs == 3) {
-        if (nkwargs == 1) {
-            PyObject *key = PyTuple_GET_ITEM(kwnames, 0);
-            if (!_PyUnicode_EqualToASCIIString(key, "errors")) {
-                PyErr_Format(PyExc_TypeError,
-                    "str() got an unexpected keyword argument %R", key);
-                return NULL;
-            }
-        }
-        else if (nkwargs != 0) {
-            return fallback_to_tp_call(type, nargs, nkwargs, args, kwnames);
-        }
-        const char *encoding = as_const_char(args[1], "encoding");
-        if (encoding == NULL) {
+    if (nkwargs) {
+        // Fallback to tp_call()
+        PyObject *tuple = _PyTuple_FromArray(args, nargs);
+        if (tuple == NULL) {
             return NULL;
         }
-        const char *errors = as_const_char(args[2], "errors");
-        if (errors == NULL) {
+        PyObject *dict = _PyStack_AsDict(args + nargs, kwnames);
+        if (dict == NULL) {
+            Py_DECREF(tuple);
             return NULL;
         }
-        return PyUnicode_FromEncodedObject(object, encoding, errors);
+        return unicode_new(_PyType_CAST(type), tuple, dict);
     }
     if (nargs > 3) {
         PyErr_Format(PyExc_TypeError,
             "str() takes at most 3 arguments (%d given)", nargs + nkwargs);
         return NULL;
     }
-
-    return fallback_to_tp_call(type, nargs, nkwargs, args, kwnames);
+    if (nargs == 0) {
+        return unicode_get_empty();
+    }
+    PyObject *object = args[0];
+    if (nargs == 1) {
+        return PyObject_Str(object);
+    }
+    const char *encoding = NULL;
+    const char *errors = NULL;
+    if (nargs == 2) {
+        encoding = as_const_char(args[1], "encoding");
+    }
+    if (nargs == 3) {
+        encoding = as_const_char(args[1], "encoding");
+        errors = as_const_char(args[1], "errors");
+    }
+    return PyUnicode_FromEncodedObject(object, encoding, errors);
 }
 
 static PyObject *

From 9319c963295a53f70f5e455d1beb4769b844ace5 Mon Sep 17 00:00:00 2001
From: "Erlend E. Aasland" <erlend.aasland@protonmail.com>
Date: Thu, 11 Apr 2024 10:32:55 +0200
Subject: [PATCH 11/17] Update Objects/unicodeobject.c

---
 Objects/unicodeobject.c | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 307c0b30e57538..055fff74a3c59b 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -14666,15 +14666,8 @@ unicode_vectorcall(PyObject *type, PyObject *const *args,
     if (nargs == 1) {
         return PyObject_Str(object);
     }
-    const char *encoding = NULL;
-    const char *errors = NULL;
-    if (nargs == 2) {
-        encoding = as_const_char(args[1], "encoding");
-    }
-    if (nargs == 3) {
-        encoding = as_const_char(args[1], "encoding");
-        errors = as_const_char(args[1], "errors");
-    }
+    const char *encoding = as_const_char(args[1], "encoding");
+    const char *errors = (nargs == 2) ? NULL : as_const_char(args[2], "errors");
     return PyUnicode_FromEncodedObject(object, encoding, errors);
 }
 

From b069905911d093173ec111e2d8ea389d1d29aaf0 Mon Sep 17 00:00:00 2001
From: "Erlend E. Aasland" <erlend.aasland@protonmail.com>
Date: Thu, 11 Apr 2024 10:34:13 +0200
Subject: [PATCH 12/17] Update Misc/NEWS.d/next/Core and
 Builtins/2024-04-10-22-16-18.gh-issue-117709.-_1YL0.rst

---
 .../2024-04-10-22-16-18.gh-issue-117709.-_1YL0.rst           | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/Misc/NEWS.d/next/Core and Builtins/2024-04-10-22-16-18.gh-issue-117709.-_1YL0.rst b/Misc/NEWS.d/next/Core and Builtins/2024-04-10-22-16-18.gh-issue-117709.-_1YL0.rst
index 1877ac5818cb69..2216b53688c378 100644
--- a/Misc/NEWS.d/next/Core and Builtins/2024-04-10-22-16-18.gh-issue-117709.-_1YL0.rst	
+++ b/Misc/NEWS.d/next/Core and Builtins/2024-04-10-22-16-18.gh-issue-117709.-_1YL0.rst	
@@ -1,2 +1,3 @@
-Speed up calls to :func:`str` by using the :pep:`590` ``vectorcall`` calling
-convention. Patch by Erlend Aasland.
+Speed up calls to :func:`str` with positional-only argument,
+by using the :pep:`590` ``vectorcall`` calling convention.
+Patch by Erlend Aasland.

From 519e7949bb292354b7cf33f91e44fd378c922328 Mon Sep 17 00:00:00 2001
From: "Erlend E. Aasland" <erlend@python.org>
Date: Thu, 11 Apr 2024 13:11:46 +0200
Subject: [PATCH 13/17] Address review

---
 Objects/unicodeobject.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 055fff74a3c59b..045515294c3190 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -14618,7 +14618,7 @@ unicode_new_impl(PyTypeObject *type, PyObject *x, const char *encoding,
 }
 
 static const char *
-as_const_char(PyObject *obj, const char *name)
+arg_as_utf8(PyObject *obj, const char *name)
 {
     if (!PyUnicode_Check(obj)) {
         PyErr_Format(PyExc_TypeError,
@@ -14640,9 +14640,8 @@ unicode_vectorcall(PyObject *type, PyObject *const *args,
     assert(Py_Is(_PyType_CAST(type), &PyUnicode_Type));
 
     Py_ssize_t nargs = PyVectorcall_NARGS(nargsf);
-    Py_ssize_t nkwargs = (kwnames) ? PyTuple_GET_SIZE(kwnames) : 0;
-    if (nkwargs) {
-        // Fallback to tp_call()
+    if (kwnames != NULL && PyTuple_GET_SIZE(kwnames) != 0) {
+        // Fallback to unicode_new()
         PyObject *tuple = _PyTuple_FromArray(args, nargs);
         if (tuple == NULL) {
             return NULL;
@@ -14652,11 +14651,14 @@ unicode_vectorcall(PyObject *type, PyObject *const *args,
             Py_DECREF(tuple);
             return NULL;
         }
-        return unicode_new(_PyType_CAST(type), tuple, dict);
+        PyObject *ret = unicode_new(_PyType_CAST(type), tuple, dict);
+        Py_DECREF(tuple);
+        Py_DECREF(dict);
+        return ret;
     }
     if (nargs > 3) {
         PyErr_Format(PyExc_TypeError,
-            "str() takes at most 3 arguments (%d given)", nargs + nkwargs);
+            "str() takes at most 3 arguments (%d given)", nargs);
         return NULL;
     }
     if (nargs == 0) {
@@ -14666,8 +14668,8 @@ unicode_vectorcall(PyObject *type, PyObject *const *args,
     if (nargs == 1) {
         return PyObject_Str(object);
     }
-    const char *encoding = as_const_char(args[1], "encoding");
-    const char *errors = (nargs == 2) ? NULL : as_const_char(args[2], "errors");
+    const char *encoding = arg_as_utf8(args[1], "encoding");
+    const char *errors = (nargs == 2) ? NULL : arg_as_utf8(args[2], "errors");
     return PyUnicode_FromEncodedObject(object, encoding, errors);
 }
 

From 8138db40dd06d639d443baeddf09e709e6b6494b Mon Sep 17 00:00:00 2001
From: "Erlend E. Aasland" <erlend@python.org>
Date: Thu, 11 Apr 2024 14:42:57 +0200
Subject: [PATCH 14/17] Add more tests

---
 Lib/test/test_str.py | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/Lib/test/test_str.py b/Lib/test/test_str.py
index b4927113db44e3..ea37eb5d96457d 100644
--- a/Lib/test/test_str.py
+++ b/Lib/test/test_str.py
@@ -2651,6 +2651,24 @@ def test_check_encoding_errors(self):
         proc = assert_python_failure('-X', 'dev', '-c', code)
         self.assertEqual(proc.rc, 10, proc)
 
+    def test_str_invalid_call(self):
+        check = lambda *a, **kw: self.assertRaises(TypeError, str, *a, **kw)
+
+        # too many args
+        check(1, "", "", 1)
+
+        # no such kw arg
+        check(test=1)
+
+        # 'encoding' must be str
+        check(1, encoding=1)
+        check(1, 1)
+
+        # 'errors' must be str
+        check(1, errors=1)
+        check(1, "", errors=1)
+        check(1, 1, 1)
+
 
 class StringModuleTest(unittest.TestCase):
     def test_formatter_parser(self):

From 906f2d1d4e18eb1bbab85d97ef81105118bb3cb8 Mon Sep 17 00:00:00 2001
From: "Erlend E. Aasland" <erlend.aasland@protonmail.com>
Date: Thu, 11 Apr 2024 14:54:36 +0200
Subject: [PATCH 15/17] Update Objects/unicodeobject.c

---
 Objects/unicodeobject.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 045515294c3190..860e0df427782b 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -14669,7 +14669,7 @@ unicode_vectorcall(PyObject *type, PyObject *const *args,
         return PyObject_Str(object);
     }
     const char *encoding = arg_as_utf8(args[1], "encoding");
-    const char *errors = (nargs == 2) ? NULL : arg_as_utf8(args[2], "errors");
+    const char *errors = (nargs == 3) ? arg_as_utf8(args[2], "errors") : NULL;
     return PyUnicode_FromEncodedObject(object, encoding, errors);
 }
 

From 4a533c0ca6fd49296719256990aa5c20dfe0dbcc Mon Sep 17 00:00:00 2001
From: "Erlend E. Aasland" <erlend.aasland@protonmail.com>
Date: Thu, 11 Apr 2024 15:12:07 +0200
Subject: [PATCH 16/17] Address review: use _PyArg_CheckPositional

---
 Objects/unicodeobject.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 860e0df427782b..0be82d7d9f3fbe 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -14656,9 +14656,7 @@ unicode_vectorcall(PyObject *type, PyObject *const *args,
         Py_DECREF(dict);
         return ret;
     }
-    if (nargs > 3) {
-        PyErr_Format(PyExc_TypeError,
-            "str() takes at most 3 arguments (%d given)", nargs);
+    if (!_PyArg_CheckPositional("str", nargs, 0, 3)) {
         return NULL;
     }
     if (nargs == 0) {

From 162a7ef0d29f643b168e9b9b89a4bdc807cdbaa1 Mon Sep 17 00:00:00 2001
From: "Erlend E. Aasland" <erlend.aasland@protonmail.com>
Date: Thu, 11 Apr 2024 15:26:15 +0200
Subject: [PATCH 17/17] Update Objects/unicodeobject.c

Co-authored-by: Victor Stinner <vstinner@python.org>
---
 Objects/unicodeobject.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 0be82d7d9f3fbe..2c259b7e869efe 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -14626,11 +14626,7 @@ arg_as_utf8(PyObject *obj, const char *name)
                      name, obj);
         return NULL;
     }
-    const char *str = _PyUnicode_AsUTF8NoNUL(obj);
-    if (str == NULL) {
-        return NULL;
-    }
-    return str;
+    return _PyUnicode_AsUTF8NoNUL(obj);
 }
 
 static PyObject *