Refactor print_error_text()

Author: gvanrossum

Python/pythonrun.c

@@ -554,36 +554,58 @@ parse_syntax_error(PyObject *err, PyObject **message, PyObject **filename,
 static void
 print_error_text(PyObject *f, int offset, PyObject *text_obj)
 {
- const char *text;
- const char *nl;
-
- text = PyUnicode_AsUTF8(text_obj);
+ /* Convert text to a char pointer; return if error */
+ const char *text = PyUnicode_AsUTF8(text_obj);
  if (text == NULL)
  return;
 
- if (offset >= 0) {
- if (offset > 0 && (size_t)offset == strlen(text) && text[offset - 1] == '\n')
- offset--;
- for (;;) {
- nl = strchr(text, '\n');
- if (nl == NULL || nl-text >= offset)
- break;
- offset -= (int)(nl+1-text);
- text = nl+1;
- }
- while (*text == ' ' || *text == '\t' || *text == '\f') {
- text++;
- offset--;
- }
+ /* Convert offset from 1-based to 0-based */
+ offset--;
+
+ /* Strip leading whitespace from text, adjusting offset as we go */
+ while (*text == ' ' || *text == '\t' || *text == '\f') {
+ text++;
+ offset--;
+ }
+
+ /* Calculate text length excluding trailing newline */
+ Py_ssize_t len = strlen(text);
+ if (len > 0 && text[len-1] == '\n')
+ len--;
+
+ /* Clip offset to at most len */
+ if (offset > len)
+ offset = len;
+
+ /* Skip past newlines embedded in text */
+ for (;;) {
+ const char *nl = strchr(text, '\n');
+ if (nl == NULL)
+ break;
+ Py_ssize_t inl = nl - text;
+ if (inl >= (Py_ssize_t)offset)
+ break;
+ inl += 1;
+ text += inl;
+ len -= inl;
+ offset -= (int)inl;
  }
+
+ /* Print text */
  PyFile_WriteString(" ", f);
  PyFile_WriteString(text, f);
- if (*text == '\0' || text[strlen(text)-1] != '\n')
+
+ /* Make sure there's a newline at the end */
+ if (text[len] != '\n')
  PyFile_WriteString("\n", f);
- if (offset == -1)
+
+ /* Don't print caret if it points to the left of the text */
+ if (offset < 0)
  return;
+
+ /* Write caret line */
  PyFile_WriteString(" ", f);
- while (--offset > 0)
+ while (--offset >= 0)
  PyFile_WriteString(" ", f);
  PyFile_WriteString("^\n", f);
 }