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gh-90102: Remove isatty call during regular open (#124922)

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Co-authored-by: Victor Stinner <vstinner@python.org>
This commit is contained in:
Cody Maloney 2024-10-07 23:50:42 -07:00 • committed by GitHub
parent 6e3c70c61b
commit cc9b9bebb2
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GPG key ID: B5690EEEBB952194
9 changed files with 47 additions and 5 deletions
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2
Modules/_io/_iomodule.c
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@ -346,7 +346,7 @@ _io_open_impl(PyObject *module, PyObject *file, const char *mode,
/* buffering */
if (buffering < 0) {
PyObject *res = PyObject_CallMethodNoArgs(raw, &_Py_ID(isatty));
PyObject *res = PyObject_CallMethodNoArgs(raw, &_Py_ID(_isatty_open_only));
if (res == NULL)
goto error;
isatty = PyObject_IsTrue(res);

22
Modules/_io/fileio.c
View file

@ -12,9 +12,6 @@
#ifdef HAVE_SYS_TYPES_H
# include <sys/types.h>
#endif
#ifdef HAVE_SYS_STAT_H
# include <sys/stat.h>
#endif
#ifdef HAVE_IO_H
# include <io.h>
#endif
@ -1218,6 +1215,24 @@ _io_FileIO_isatty_impl(fileio *self)
return PyBool_FromLong(res);
}
/* Checks whether the file is a TTY using an open-only optimization.
TTYs are always character devices. If the interpreter knows a file is
not a character device when it would call ``isatty``, can skip that
call. Inside ``open()`` there is a fresh stat result that contains that
information. Use the stat result to skip a system call. Outside of that
context TOCTOU issues (the fd could be arbitrarily modified by
surrounding code). */
static PyObject *
_io_FileIO_isatty_open_only(PyObject *op, PyObject *Py_UNUSED(ignored))
{
fileio *self = _PyFileIO_CAST(op);
if (self->stat_atopen != NULL && !S_ISCHR(self->stat_atopen->st_mode)) {
Py_RETURN_FALSE;
}
return _io_FileIO_isatty_impl(self);
}
#include "clinic/fileio.c.h"
static PyMethodDef fileio_methods[] = {
@ -1234,6 +1249,7 @@ static PyMethodDef fileio_methods[] = {
_IO_FILEIO_WRITABLE_METHODDEF
_IO_FILEIO_FILENO_METHODDEF
_IO_FILEIO_ISATTY_METHODDEF
{"_isatty_open_only", _io_FileIO_isatty_open_only, METH_NOARGS},
{"_dealloc_warn", fileio_dealloc_warn, METH_O, NULL},
{"__reduce__", _PyIOBase_cannot_pickle, METH_NOARGS},
{"__reduce_ex__", _PyIOBase_cannot_pickle, METH_O},

1
Modules/_io/winconsoleio.c
View file

@ -1128,6 +1128,7 @@ static PyMethodDef winconsoleio_methods[] = {
_IO__WINDOWSCONSOLEIO_WRITABLE_METHODDEF
_IO__WINDOWSCONSOLEIO_FILENO_METHODDEF
_IO__WINDOWSCONSOLEIO_ISATTY_METHODDEF
{"_isatty_open_only", (PyCFunction)_io__WindowsConsoleIO_isatty, METH_NOARGS},
{NULL, NULL} /* sentinel */
};