bpo-32228: Reset raw_pos after unwinding the raw stream (#4858)
Ensure that ``truncate()`` preserves the file position (as reported by ``tell()``) after writes longer than the buffer size.
diff --git a/Modules/_io/bufferedio.c b/Modules/_io/bufferedio.c
index 2b7aaaf..358a654 100644
--- a/Modules/_io/bufferedio.c
+++ b/Modules/_io/bufferedio.c
@@ -1292,7 +1292,6 @@
if (res == NULL)
goto end;
Py_CLEAR(res);
- _bufferedwriter_reset_buf(self);
}
/* TODO: align on block boundary and read buffer if needed? */
@@ -1852,8 +1851,6 @@
return n;
}
-/* `restore_pos` is 1 if we need to restore the raw stream position at
- the end, 0 otherwise. */
static PyObject *
_bufferedwriter_flush_unlocked(buffered *self)
{
@@ -1894,9 +1891,18 @@
goto error;
}
- _bufferedwriter_reset_buf(self);
end:
+ /* This ensures that after return from this function,
+ VALID_WRITE_BUFFER(self) returns false.
+
+ This is a required condition because when a tell() is called
+ after flushing and if VALID_READ_BUFFER(self) is false, we need
+ VALID_WRITE_BUFFER(self) to be false to have
+ RAW_OFFSET(self) == 0.
+
+ Issue: https://bugs.python.org/issue32228 */
+ _bufferedwriter_reset_buf(self);
Py_RETURN_NONE;
error: