Use _PyUnicodeWriter API in str.format() internals

Objects/floatobject.c

 
 /* Float object implementation */
 
 /* XXX There should be overflow checks here, but it's hard to check
    for any kind of float exception without losing portability. */
 
 #include "Python.h"
 
 #include <ctype.h>
 #include <float.h>
@@ skipping 255 matching lines @@
 static PyObject *
 float_repr(PyFloatObject *v)
 {
     PyObject *result;
     char *buf = PyOS_double_to_string(PyFloat_AS_DOUBLE(v),
                                       'r', 0,
                                       Py_DTSF_ADD_DOT_0,
                                       NULL);
     if (!buf)
         return PyErr_NoMemory();
-    result = PyUnicode_FromString(buf);
+    result = PyUnicode_FromKindAndData(PyUnicode_1BYTE_KIND,
+                                       buf, strlen(buf));
     PyMem_Free(buf);
     return result;
 }
 
 /* Comparison is pretty much a nightmare.  When comparing float to float,
  * we do it as straightforwardly (and long-windedly) as conceivable, so
  * that, e.g., Python x == y delivers the same result as the platform
  * C x == y when x and/or y is a NaN.
  * When mixing float with an integer type, there's no good *uniform* approach.
  * Converting the double to an integer obviously doesn't work, since we
@@ skipping 1409 matching lines @@
 static PyObject *
 float_getzero(PyObject *v, void *closure)
 {
     return PyFloat_FromDouble(0.0);
 }
 
 static PyObject *
 float__format__(PyObject *self, PyObject *args)
 {
     PyObject *format_spec;
+    _PyUnicodeWriter writer;
+    int ret;
 
     if (!PyArg_ParseTuple(args, "U:__format__", &format_spec))
         return NULL;
-    return _PyFloat_FormatAdvanced(self, format_spec, 0,
-                                   PyUnicode_GET_LENGTH(format_spec));
+
+    _PyUnicodeWriter_Init(&writer, 0);
+    ret = _PyFloat_FormatAdvancedWriter(
+        self,
+        format_spec, 0, PyUnicode_GET_LENGTH(format_spec),
+        &writer);
+    if (ret == -1) {
+        _PyUnicodeWriter_Dealloc(&writer);
+        return NULL;
+    }
+    return _PyUnicodeWriter_Finish(&writer);
 }
 
 PyDoc_STRVAR(float__format__doc,
 "float.__format__(format_spec) -> string\n"
 "\n"
 "Formats the float according to format_spec.");
 
 
 static PyMethodDef float_methods[] = {
     {"conjugate",       (PyCFunction)float_float,       METH_NOARGS,
@@ skipping 601 matching lines @@
             }
             memcpy(&x, buf, 8);
         }
         else {
             memcpy(&x, p, 8);
         }
 
         return x;
     }
 }