Issue #27078: Added BUILD_STRING opcode. Optimized f-strings evaluation.

2 files changed, 43 insertions, 19 deletions

diff --git a/Objects/abstract.c b/Objects/abstract.c
index 654fc02..d876dc5 100644
--- a/Objects/abstract.c
+++ b/Objects/abstract.c
@@ -675,13 +675,31 @@ PyObject_Format(PyObject *obj, PyObject *format_spec)
     PyObject *result = NULL;
     _Py_IDENTIFIER(__format__);
 
+    if (format_spec != NULL && !PyUnicode_Check(format_spec)) {
+        PyErr_Format(PyExc_SystemError,
+                     "Format specifier must be a string, not %.200s",
+                     Py_TYPE(format_spec)->tp_name);
+        return NULL;
+    }
+
+    /* Fast path for common types. */
+    if (format_spec == NULL || PyUnicode_GET_LENGTH(format_spec) == 0) {
+        if (PyUnicode_CheckExact(obj)) {
+            Py_INCREF(obj);
+            return obj;
+        }
+        if (PyLong_CheckExact(obj)) {
+            return PyObject_Str(obj);
+        }
+    }
+
     /* If no format_spec is provided, use an empty string */
     if (format_spec == NULL) {
         empty = PyUnicode_New(0, 0);
         format_spec = empty;
     }
 
-    /* Find the (unbound!) __format__ method (a borrowed reference) */
+    /* Find the (unbound!) __format__ method */
     meth = _PyObject_LookupSpecial(obj, &PyId___format__);
     if (meth == NULL) {
         if (!PyErr_Occurred())
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 12d09f0..4256d05 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -9892,20 +9892,10 @@ case_operation(PyObject *self,
 PyObject *
 PyUnicode_Join(PyObject *separator, PyObject *seq)
 {
-    PyObject *sep = NULL;
-    Py_ssize_t seplen;
-    PyObject *res = NULL; /* the result */
-    PyObject *fseq;          /* PySequence_Fast(seq) */
-    Py_ssize_t seqlen;       /* len(fseq) -- number of items in sequence */
+    PyObject *res;
+    PyObject *fseq;
+    Py_ssize_t seqlen;
     PyObject **items;
-    PyObject *item;
-    Py_ssize_t sz, i, res_offset;
-    Py_UCS4 maxchar;
-    Py_UCS4 item_maxchar;
-    int use_memcpy;
-    unsigned char *res_data = NULL, *sep_data = NULL;
-    PyObject *last_obj;
-    unsigned int kind = 0;
 
     fseq = PySequence_Fast(seq, "can only join an iterable");
     if (fseq == NULL) {
@@ -9916,21 +9906,39 @@ PyUnicode_Join(PyObject *separator, PyObject *seq)
      * so we are sure that fseq won't be mutated.
      */
 
+    items = PySequence_Fast_ITEMS(fseq);
     seqlen = PySequence_Fast_GET_SIZE(fseq);
+    res = _PyUnicode_JoinArray(separator, items, seqlen);
+    Py_DECREF(fseq);
+    return res;
+}
+
+PyObject *
+_PyUnicode_JoinArray(PyObject *separator, PyObject **items, Py_ssize_t seqlen)
+{
+    PyObject *res = NULL; /* the result */
+    PyObject *sep = NULL;
+    Py_ssize_t seplen;
+    PyObject *item;
+    Py_ssize_t sz, i, res_offset;
+    Py_UCS4 maxchar;
+    Py_UCS4 item_maxchar;
+    int use_memcpy;
+    unsigned char *res_data = NULL, *sep_data = NULL;
+    PyObject *last_obj;
+    unsigned int kind = 0;
+
     /* If empty sequence, return u"". */
     if (seqlen == 0) {
-        Py_DECREF(fseq);
         _Py_RETURN_UNICODE_EMPTY();
     }
 
     /* If singleton sequence with an exact Unicode, return that. */
     last_obj = NULL;
-    items = PySequence_Fast_ITEMS(fseq);
     if (seqlen == 1) {
         if (PyUnicode_CheckExact(items[0])) {
             res = items[0];
             Py_INCREF(res);
-            Py_DECREF(fseq);
             return res;
         }
         seplen = 0;
@@ -10065,13 +10073,11 @@ PyUnicode_Join(PyObject *separator, PyObject *seq)
         assert(res_offset == PyUnicode_GET_LENGTH(res));
     }
 
-    Py_DECREF(fseq);
     Py_XDECREF(sep);
     assert(_PyUnicode_CheckConsistency(res, 1));
     return res;
 
   onError:
-    Py_DECREF(fseq);
     Py_XDECREF(sep);
     Py_XDECREF(res);
     return NULL;