diff options
| -rw-r--r-- | Lib/importlib/_bootstrap.py | 35 | ||||
| -rw-r--r-- | Misc/NEWS | 2 | ||||
| -rw-r--r-- | Python/import.c | 48 |
3 files changed, 60 insertions, 25 deletions
diff --git a/Lib/importlib/_bootstrap.py b/Lib/importlib/_bootstrap.py index 209e041..359b9e7 100644 --- a/Lib/importlib/_bootstrap.py +++ b/Lib/importlib/_bootstrap.py @@ -84,24 +84,29 @@ def _write_atomic(path, data): """Best-effort function to write data to a path atomically. Be prepared to handle a FileExistsError if concurrent writing of the temporary file is attempted.""" - if not sys.platform.startswith('win'): - # On POSIX-like platforms, renaming is atomic. id() is used to generate - # a pseudo-random filename. - path_tmp = '{}.{}'.format(path, id(path)) - fd = _os.open(path_tmp, _os.O_EXCL | _os.O_CREAT | _os.O_WRONLY, 0o666) + # Renaming should be atomic on most platforms (including Windows). + # Under Windows, the limitation is that we can't rename() to an existing + # path, while POSIX will overwrite it. But here we don't really care + # if there is a glimpse of time during which the final pyc file doesn't + # exist. + # id() is used to generate a pseudo-random filename. + path_tmp = '{}.{}'.format(path, id(path)) + fd = _os.open(path_tmp, _os.O_EXCL | _os.O_CREAT | _os.O_WRONLY, 0o666) + try: + with _io.FileIO(fd, 'wb') as file: + file.write(data) try: - with _io.FileIO(fd, 'wb') as file: - file.write(data) _os.rename(path_tmp, path) + except FileExistsError: + # Windows (if we had access to MoveFileEx, we could overwrite) + _os.unlink(path) + _os.rename(path_tmp, path) + except OSError: + try: + _os.unlink(path_tmp) except OSError: - try: - _os.unlink(path_tmp) - except OSError: - pass - raise - else: - with _io.FileIO(path, 'wb') as file: - file.write(data) + pass + raise def _wrap(new, old): @@ -10,6 +10,8 @@ What's New in Python 3.3 Alpha 1? Core and Builtins ----------------- +- Issue #13392: Writing a pyc file should now be atomic under Windows as well. + - Issue #13333: The UTF-7 decoder now accepts lone surrogates (the encoder already accepts them). diff --git a/Python/import.c b/Python/import.c index ae1101e..3c3e504 100644 --- a/Python/import.c +++ b/Python/import.c @@ -1197,6 +1197,8 @@ write_compiled_module(PyCodeObject *co, PyObject *cpathname, time_t mtime = srcstat->st_mtime; #ifdef MS_WINDOWS /* since Windows uses different permissions */ mode_t mode = srcstat->st_mode & ~S_IEXEC; + PyObject *cpathname_tmp; + Py_ssize_t cpathname_len; #else mode_t dirmode = (srcstat->st_mode | S_IXUSR | S_IXGRP | S_IXOTH | @@ -1255,18 +1257,29 @@ write_compiled_module(PyCodeObject *co, PyObject *cpathname, } Py_DECREF(dirname); + /* We first write to a tmp file and then take advantage + of atomic renaming (which *should* be true even under Windows). */ #ifdef MS_WINDOWS - (void)DeleteFileW(PyUnicode_AS_UNICODE(cpathname)); - fd = _wopen(PyUnicode_AS_UNICODE(cpathname), - O_EXCL | O_CREAT | O_WRONLY | O_TRUNC | O_BINARY, - mode); + cpathname_len = PyUnicode_GET_LENGTH(cpathname); + cpathname_tmp = PyUnicode_New(cpathname_len + 4, + PyUnicode_MAX_CHAR_VALUE(cpathname)); + if (cpathname_tmp == NULL) { + PyErr_Clear(); + return; + } + PyUnicode_WriteChar(cpathname_tmp, cpathname_len + 0, '.'); + PyUnicode_WriteChar(cpathname_tmp, cpathname_len + 1, 't'); + PyUnicode_WriteChar(cpathname_tmp, cpathname_len + 2, 'm'); + PyUnicode_WriteChar(cpathname_tmp, cpathname_len + 3, 'p'); + (void)DeleteFileW(PyUnicode_AS_UNICODE(cpathname_tmp)); + fd = _wopen(PyUnicode_AS_UNICODE(cpathname_tmp), + O_EXCL | O_CREAT | O_WRONLY | O_BINARY, + mode); if (0 <= fd) fp = fdopen(fd, "wb"); else fp = NULL; #else - /* Under POSIX, we first write to a tmp file and then take advantage - of atomic renaming. */ cpathbytes = PyUnicode_EncodeFSDefault(cpathname); if (cpathbytes == NULL) { PyErr_Clear(); @@ -1294,7 +1307,9 @@ write_compiled_module(PyCodeObject *co, PyObject *cpathname, if (Py_VerboseFlag) PySys_FormatStderr( "# can't create %R\n", cpathname); -#ifndef MS_WINDOWS +#ifdef MS_WINDOWS + Py_DECREF(cpathname_tmp); +#else Py_DECREF(cpathbytes); Py_DECREF(cpathbytes_tmp); #endif @@ -1315,7 +1330,8 @@ write_compiled_module(PyCodeObject *co, PyObject *cpathname, /* Don't keep partial file */ fclose(fp); #ifdef MS_WINDOWS - (void)DeleteFileW(PyUnicode_AS_UNICODE(cpathname)); + (void)DeleteFileW(PyUnicode_AS_UNICODE(cpathname_tmp)); + Py_DECREF(cpathname_tmp); #else (void) unlink(PyBytes_AS_STRING(cpathbytes_tmp)); Py_DECREF(cpathbytes); @@ -1324,8 +1340,20 @@ write_compiled_module(PyCodeObject *co, PyObject *cpathname, return; } fclose(fp); - /* Under POSIX, do an atomic rename */ -#ifndef MS_WINDOWS + /* Do a (hopefully) atomic rename */ +#ifdef MS_WINDOWS + if (!MoveFileExW(PyUnicode_AS_UNICODE(cpathname_tmp), + PyUnicode_AS_UNICODE(cpathname), + MOVEFILE_REPLACE_EXISTING)) { + if (Py_VerboseFlag) + PySys_FormatStderr("# can't write %R\n", cpathname); + /* Don't keep tmp file */ + (void) DeleteFileW(PyUnicode_AS_UNICODE(cpathname_tmp)); + Py_DECREF(cpathname_tmp); + return; + } + Py_DECREF(cpathname_tmp); +#else if (rename(PyBytes_AS_STRING(cpathbytes_tmp), PyBytes_AS_STRING(cpathbytes))) { if (Py_VerboseFlag) |