Add _PyUnicodeWriter_FormatV

Author: encukou

Include/internal/pycore_unicodeobject.h

@@ -82,6 +82,12 @@ extern int _PyUnicode_FormatAdvancedWriter(
     Py_ssize_t start,
     Py_ssize_t end);
 
+/* PyUnicodeWriter_Format, with va_list instead of `...` */
+extern int _PyUnicodeWriter_FormatV(
+    PyUnicodeWriter *writer,
+    const char *format,
+    va_list vargs);
+
 /* --- UTF-7 Codecs ------------------------------------------------------- */
 
 extern PyObject* _PyUnicode_EncodeUTF7(

Objects/unicodeobject.c

@@ -3271,14 +3271,22 @@ PyUnicode_FromFormat(const char *format, ...)
 
 int
 PyUnicodeWriter_Format(PyUnicodeWriter *writer, const char *format, ...)
+{
+    va_list vargs;
+    va_start(vargs, format);
+    int res = _PyUnicodeWriter_FormatV(writer, format, vargs);
+    va_end(vargs);
+    return res;
+}
+
+int
+_PyUnicodeWriter_FormatV(PyUnicodeWriter *writer, const char *format,
+                         va_list vargs)
 {
     _PyUnicodeWriter *_writer = (_PyUnicodeWriter*)writer;
     Py_ssize_t old_pos = _writer->pos;
 
-    va_list vargs;
-    va_start(vargs, format);
     int res = unicode_from_format(_writer, format, vargs);
-    va_end(vargs);
 
     if (res < 0) {
         _writer->pos = old_pos;