Close #17694: Add minimum length to _PyUnicodeWriter

 * Add also min_char attribute to _PyUnicodeWriter structure (currently unused)
 * _PyUnicodeWriter_Init() has no more argument (except the writer itself):
   min_length and overallocate must be set explicitly
 * In error handlers, only enable overallocation if the replacement string
   is longer than 1 character
 * CJK decoders don't use overallocation anymore
 * Set min_length, instead of preallocating memory using
   _PyUnicodeWriter_Prepare(), in many decoders
 * _PyUnicode_DecodeUnicodeInternal() checks for integer overflow

1 files changed, 3 insertions, 3 deletions

diff --git a/Objects/stringlib/unicode_format.h b/Objects/stringlib/unicode_format.h
index 2f58946..9429169 100644
--- a/Objects/stringlib/unicode_format.h
+++ b/Objects/stringlib/unicode_format.h
@@ -906,7 +906,6 @@ build_string(SubString *input, PyObject *args, PyObject *kwargs,
              int recursion_depth, AutoNumber *auto_number)
 {
     _PyUnicodeWriter writer;
-    Py_ssize_t minlen;
 
     /* check the recursion level */
     if (recursion_depth <= 0) {
@@ -915,8 +914,9 @@ build_string(SubString *input, PyObject *args, PyObject *kwargs,
         return NULL;
     }
 
-    minlen = PyUnicode_GET_LENGTH(input->str) + 100;
-    _PyUnicodeWriter_Init(&writer, minlen);
+    _PyUnicodeWriter_Init(&writer);
+    writer.overallocate = 1;
+    writer.min_length = PyUnicode_GET_LENGTH(input->str) + 100;
 
     if (!do_markup(input, args, kwargs, &writer, recursion_depth,
                    auto_number)) {