https://github.com/python/cpython/commit/e22d4a0ba7b4cc199fccf259d7e1b9b37a5cc971
commit: e22d4a0ba7b4cc199fccf259d7e1b9b37a5cc971
branch: 3.13
author: Serhiy Storchaka <[email protected]>
committer: serhiy-storchaka <[email protected]>
date: 2026-09-04T11:43:14Z
summary:

[3.13] gh-156894: Fix the position of syntax errors which cover a range 
(GH-156901) (GH-156928)

The callers of _PyTokenizer_syntaxerror_known_range() pass columns in bytes,
but SyntaxError.offset and end_offset are columns in characters.

(cherry picked from commit 59a691361cb7b1d4fde3b92f98a61490381c62c9)

Co-authored-by: Claude Opus 5 (1M context) <[email protected]>

files:
A 
Misc/NEWS.d/next/Core_and_Builtins/2026-09-03-15-20-00.gh-issue-156894.Rt9Bx4.rst
M Lib/test/test_exceptions.py
M Parser/tokenizer/helpers.c

diff --git a/Lib/test/test_exceptions.py b/Lib/test/test_exceptions.py
index e34bd7b83a19b03..f8d06b469b651e2 100644
--- a/Lib/test/test_exceptions.py
+++ b/Lib/test/test_exceptions.py
@@ -230,6 +230,23 @@ def test_error_offset_continuation_characters(self):
         check = self.check
         check('"\\\n"(1 for c in I,\\\n\\', 2, 2)
 
+    def testSyntaxErrorRange(self):
+        # gh-156894: the position was reported in bytes, not in characters,
+        # for the errors which cover a range
+        for source, offset, end_offset in [
+            ('abcd = 00010', 8, 11),
+            ('\u03b1\u03b2\u03b3\u03b4 = 00010', 8, 11),
+            ('a\u0301b\u0308c\u20d7d\u1ab0 = 00010', 12, 15),
+            ("abcd = ub'a'", 10, 13),
+            ("\u03b1\u03b2\u03b3\u03b4 = ub'a'", 10, 13),
+            ("a\u0301b\u0308c\u20d7d\u1ab0 = ub'a'", 14, 17),
+        ]:
+            with self.subTest(source=source):
+                with self.assertRaises(SyntaxError) as cm:
+                    compile(source, '<testcase>', 'exec')
+                self.assertEqual(cm.exception.offset, offset)
+                self.assertEqual(cm.exception.end_offset, end_offset)
+
     def testSyntaxErrorOffset(self):
         check = self.check
         check('def fact(x):\n\treturn x!\n', 2, 10)
diff --git 
a/Misc/NEWS.d/next/Core_and_Builtins/2026-09-03-15-20-00.gh-issue-156894.Rt9Bx4.rst
 
b/Misc/NEWS.d/next/Core_and_Builtins/2026-09-03-15-20-00.gh-issue-156894.Rt9Bx4.rst
new file mode 100644
index 000000000000000..9b279ab27947867
--- /dev/null
+++ 
b/Misc/NEWS.d/next/Core_and_Builtins/2026-09-03-15-20-00.gh-issue-156894.Rt9Bx4.rst
@@ -0,0 +1,2 @@
+Fix the position of syntax errors which cover a range if the line contains
+non-ASCII characters before the error.
diff --git a/Parser/tokenizer/helpers.c b/Parser/tokenizer/helpers.c
index 976d039f571554d..aad30b90cbf879c 100644
--- a/Parser/tokenizer/helpers.c
+++ b/Parser/tokenizer/helpers.c
@@ -7,6 +7,20 @@
 
 /* ############## ERRORS ############## */
 
+/* Convert a 1-based column in bytes into a 1-based column in characters.
+   The line is UTF-8 encoded, so it is enough to skip continuation bytes. */
+static int
+byte_col_to_char_col(const char *line, int byte_col)
+{
+    int char_col = 1;
+    for (int i = 0; i < byte_col - 1; i++) {
+        if ((line[i] & 0xC0) != 0x80) {
+            char_col++;
+        }
+    }
+    return char_col;
+}
+
 static int
 _syntaxerror_range(struct tok_state *tok, const char *format,
                    int col_offset, int end_col_offset,
@@ -33,9 +47,15 @@ _syntaxerror_range(struct tok_state *tok, const char *format,
     if (col_offset == -1) {
         col_offset = (int)PyUnicode_GET_LENGTH(errtext);
     }
+    else if (col_offset > 0) {
+        col_offset = byte_col_to_char_col(tok->line_start, col_offset);
+    }
     if (end_col_offset == -1) {
         end_col_offset = col_offset;
     }
+    else if (end_col_offset > 0) {
+        end_col_offset = byte_col_to_char_col(tok->line_start, end_col_offset);
+    }
 
     Py_ssize_t line_len = strcspn(tok->line_start, "\n");
     if (line_len != tok->cur - tok->line_start) {

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