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diff --git a/Lib/py_compile.py b/Lib/py_compile.py
index 978da73d74..3559eb95ca 100644
--- a/Lib/py_compile.py
+++ b/Lib/py_compile.py
@@ -120,16 +120,27 @@ def compile(file, cfile=None, dfile=None, doraise=False):
return
if cfile is None:
cfile = file + (__debug__ and 'c' or 'o')
- with open(cfile, 'wb') as fc:
- fc.write('\0\0\0\0')
- if "DETERMINISTIC_BUILD" in os.environ:
+ # Atomically write the pyc/pyo file. Issue #13146.
+ # id() is used to generate a pseudo-random filename.
+ path_tmp = '{}.{}'.format(cfile, id(cfile))
+ try:
+ with open(path_tmp, 'wb') as fc:
fc.write('\0\0\0\0')
- else:
- wr_long(fc, timestamp)
- marshal.dump(codeobject, fc)
- fc.flush()
- fc.seek(0, 0)
- fc.write(MAGIC)
+ if "DETERMINISTIC_BUILD" in os.environ:
+ fc.write('\0\0\0\0')
+ else:
+ wr_long(fc, timestamp)
+ marshal.dump(codeobject, fc)
+ fc.flush()
+ fc.seek(0, 0)
+ fc.write(MAGIC)
+ os.rename(path_tmp, cfile)
+ except OSError:
+ try:
+ os.unlink(path_tmp)
+ except OSError:
+ pass
+ raise
def main(args=None):
"""Compile several source files.
diff --git a/Python/import.c b/Python/import.c
index 1e31d79279..f78a1efcf0 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -951,6 +951,8 @@ static void
write_compiled_module(PyCodeObject *co, char *cpathname, struct stat *srcstat, time_t mtime)
{
FILE *fp;
+ size_t cpathname_len;
+ char *cpathname_tmp;
#ifdef MS_WINDOWS /* since Windows uses different permissions */
mode_t mode = srcstat->st_mode & ~S_IEXEC;
/* Issue #6074: We ensure user write access, so we can delete it later
@@ -963,11 +965,28 @@ write_compiled_module(PyCodeObject *co, char *cpathname, struct stat *srcstat, t
mode_t mode = srcstat->st_mode & ~S_IXUSR & ~S_IXGRP & ~S_IXOTH;
#endif
+#ifdef MS_WINDOWS
fp = open_exclusive(cpathname, mode);
+#else
+ /* Under POSIX, we first write to a tmp file and then take advantage
+ of atomic renaming. */
+ cpathname_len = strlen(cpathname);
+ cpathname_tmp = PyMem_MALLOC(cpathname_len + 5);
+ if (cpathname_tmp == NULL) {
+ PyErr_Clear();
+ return;
+ }
+ memcpy(cpathname_tmp, cpathname, cpathname_len);
+ memcpy(cpathname_tmp + cpathname_len, ".tmp", 5);
+ fp = open_exclusive(cpathname_tmp, mode);
+#endif
if (fp == NULL) {
if (Py_VerboseFlag)
PySys_WriteStderr(
"# can't create %s\n", cpathname);
+#ifndef MS_WINDOWS
+ PyMem_FREE(cpathname_tmp);
+#endif
return;
}
PyMarshal_WriteLongToFile(pyc_magic, fp, Py_MARSHAL_VERSION);
@@ -979,7 +998,12 @@ write_compiled_module(PyCodeObject *co, char *cpathname, struct stat *srcstat, t
PySys_WriteStderr("# can't write %s\n", cpathname);
/* Don't keep partial file */
fclose(fp);
+#ifdef MS_WINDOWS
(void) unlink(cpathname);
+#else
+ (void) unlink(cpathname_tmp);
+ PyMem_FREE(cpathname_tmp);
+#endif
return;
}
/* Now write the true mtime (as a 32-bit field) */
@@ -989,6 +1013,19 @@ write_compiled_module(PyCodeObject *co, char *cpathname, struct stat *srcstat, t
PyMarshal_WriteLongToFile((long)mtime, fp, Py_MARSHAL_VERSION);
fflush(fp);
}
+ /* Under POSIX, do an atomic rename */
+#ifndef MS_WINDOWS
+ if (rename(cpathname_tmp, cpathname)) {
+ if (Py_VerboseFlag)
+ PySys_WriteStderr("# can't write %s\n", cpathname);
+ /* Don't keep tmp file */
+ fclose(fp);
+ (void) unlink(cpathname_tmp);
+ PyMem_FREE(cpathname_tmp);
+ return;
+ }
+ PyMem_FREE(cpathname_tmp);
+#endif
fclose(fp);
if (Py_VerboseFlag)
PySys_WriteStderr("# wrote %s\n", cpathname);
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