gh-94360: Fix a tokenizer crash when reading encoded files with syntax errors from stdin (GH-94386)

* gh-94360: Fix a tokenizer crash when reading encoded files with syntax errors from stdin

Signed-off-by: Pablo Galindo <pablogsal@gmail.com>

* nitty nit

Co-authored-by: Łukasz Langa <lukasz@langa.pl>
(cherry picked from commit 36fcde61ba48c4e918830691ecf4092e4e3b9b99)

Co-authored-by: Pablo Galindo Salgado <Pablogsal@gmail.com>

1 files changed, 4 insertions, 4 deletions

diff --git a/Parser/pegen_errors.c b/Parser/pegen_errors.c
index 4896996..5703088 100644
--- a/Parser/pegen_errors.c
+++ b/Parser/pegen_errors.c
@@ -259,15 +259,15 @@ get_error_line_from_tokenizer_buffers(Parser *p, Py_ssize_t lineno)
     const char* buf_end = p->tok->fp_interactive ? p->tok->interactive_src_end : p->tok->inp;
 
     for (int i = 0; i < relative_lineno - 1; i++) {
-        char *new_line = strchr(cur_line, '\n') + 1;
+        char *new_line = strchr(cur_line, '\n');
         // The assert is here for debug builds but the conditional that
         // follows is there so in release builds we do not crash at the cost
         // to report a potentially wrong line.
-        assert(new_line != NULL && new_line <= buf_end);
-        if (new_line == NULL || new_line > buf_end) {
+        assert(new_line != NULL && new_line + 1 < buf_end);
+        if (new_line == NULL || new_line + 1 > buf_end) {
             break;
         }
-        cur_line = new_line;
+        cur_line = new_line + 1;
     }
 
     char *next_newline;