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Issue #13146: Writing a pyc file is now atomic under POSIX.

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This commit is contained in:
Antoine Pitrou 2011-10-17 19:28:44 +02:00
parent 5b9f4c1539
commit 707033a694
3 changed files with 63 additions and 14 deletions
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49
Python/import.c
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@ -1284,7 +1284,8 @@ write_compiled_module(PyCodeObject *co, PyObject *cpathname,
#ifdef MS_WINDOWS
int fd;
#else
PyObject *cpathbytes;
PyObject *cpathbytes, *cpathbytes_tmp;
Py_ssize_t cpathbytes_len;
#endif
PyObject *dirname;
Py_UCS4 *dirsep;
@ -1345,13 +1346,25 @@ write_compiled_module(PyCodeObject *co, PyObject *cpathname,
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();
return;
}
cpathbytes_len = PyBytes_GET_SIZE(cpathbytes);
cpathbytes_tmp = PyBytes_FromStringAndSize(NULL, cpathbytes_len + 4);
if (cpathbytes_tmp == NULL) {
Py_DECREF(cpathbytes);
PyErr_Clear();
return;
}
memcpy(PyBytes_AS_STRING(cpathbytes_tmp), PyBytes_AS_STRING(cpathbytes),
cpathbytes_len);
memcpy(PyBytes_AS_STRING(cpathbytes_tmp) + cpathbytes_len, ".tmp", 4);
fp = open_exclusive(PyBytes_AS_STRING(cpathbytes), mode);
fp = open_exclusive(PyBytes_AS_STRING(cpathbytes_tmp), mode);
#endif
if (fp == NULL) {
if (Py_VerboseFlag)
@ -1359,6 +1372,7 @@ write_compiled_module(PyCodeObject *co, PyObject *cpathname,
"# can't create %R\n", cpathname);
#ifndef MS_WINDOWS
Py_DECREF(cpathbytes);
Py_DECREF(cpathbytes_tmp);
#endif
return;
}
@ -1366,6 +1380,11 @@ write_compiled_module(PyCodeObject *co, PyObject *cpathname,
/* First write a 0 for mtime */
PyMarshal_WriteLongToFile(0L, fp, Py_MARSHAL_VERSION);
PyMarshal_WriteObjectToFile((PyObject *)co, fp, Py_MARSHAL_VERSION);
fflush(fp);
/* Now write the true mtime */
fseek(fp, 4L, 0);
assert(mtime < LONG_MAX);
PyMarshal_WriteLongToFile((long)mtime, fp, Py_MARSHAL_VERSION);
if (fflush(fp) != 0 || ferror(fp)) {
if (Py_VerboseFlag)
PySys_FormatStderr("# can't write %R\n", cpathname);
@ -1374,20 +1393,28 @@ write_compiled_module(PyCodeObject *co, PyObject *cpathname,
#ifdef MS_WINDOWS
(void)DeleteFileW(PyUnicode_AS_UNICODE(cpathname));
#else
(void) unlink(PyBytes_AS_STRING(cpathbytes));
(void) unlink(PyBytes_AS_STRING(cpathbytes_tmp));
Py_DECREF(cpathbytes);
Py_DECREF(cpathbytes_tmp);
#endif
return;
}
#ifndef MS_WINDOWS
Py_DECREF(cpathbytes);
#endif
/* Now write the true mtime */
fseek(fp, 4L, 0);
assert(mtime < LONG_MAX);
PyMarshal_WriteLongToFile((long)mtime, fp, Py_MARSHAL_VERSION);
fflush(fp);
fclose(fp);
/* Under POSIX, do an atomic rename */
#ifndef MS_WINDOWS
if (rename(PyBytes_AS_STRING(cpathbytes_tmp),
PyBytes_AS_STRING(cpathbytes))) {
if (Py_VerboseFlag)
PySys_FormatStderr("# can't write %R\n", cpathname);
/* Don't keep tmp file */
unlink(PyBytes_AS_STRING(cpathbytes_tmp));
Py_DECREF(cpathbytes);
Py_DECREF(cpathbytes_tmp);
return;
}
Py_DECREF(cpathbytes);
Py_DECREF(cpathbytes_tmp);
#endif
if (Py_VerboseFlag)
PySys_FormatStderr("# wrote %R\n", cpathname);
}