[patch] Use max(mtime, ctime) of source

bug256953a.patch (text/plain), 2.00 KB, created by Martin von Gagern on 2009-02-02 14:22:15 UTC

When trying to decide whether or not a given file needs to be
recompiled, the inode creation time should be taken into account along
with the file modification time.

Scenario: Suppose you have three times, A < B < C < D. At time A, you
package version 1 of foo.py. At time B, you package version 2. At time
C you install version 1 onto some system, and byte-compile it for all
users. Therefore foo.py has mtime A and ctime C, and foo.pyc has both
mtime C. At time D you delete foo.py from version 1 and install
version 2. Then you byte-compile it without force. At that time,
foo.py has mtime B (because that was when it was packaged) but ctime D
(because that was when the file was created). foo.pyc has mtime C
(because that was when it was last modified). The current comparison
compares only mtimes, sees C > B, and skips foo.py. With this patch in
place, it will check for C > max(B, D), which is not the case, and
thus recompile foo.c.

In other words, max(st_mtime, st_ctime) can be interpreted as the last
time a file at a given path was changed, either through modification
of its contents (mtime) or deletion followed by recreation
(ctime). Installation systems that overwrite files without deleting
them before still are in the same trouble as before, but all others
will benefit from this.

References:
http://bugs.python.org/issue5128
http://bugs.gentoo.org/256953

2009-02-02 Martin von Gagern

Index: Lib/compileall.py
===================================================================
--- Lib/compileall.py	(revision 69204)
+++ Lib/compileall.py	(working copy)
@@ -55,7 +55,8 @@
             head, tail = name[:-3], name[-3:]
             if tail == '.py':
                 cfile = fullname + (__debug__ and 'c' or 'o')
-                ftime = os.stat(fullname).st_mtime
+                fstat = os.stat(fullname)
+                ftime = max(fstat.st_mtime, fstat.st_ctime)
                 try: ctime = os.stat(cfile).st_mtime
                 except os.error: ctime = 0
                 if (ctime > ftime) and not force: continue