GNU bug report logs - #22533
Non-determinism in python-3 ".pyc" bytecode

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From: ludo <at> gnu.org (Ludovic Courtès)
To: Leo Famulari <leo <at> famulari.name>
Cc: 22533 <at> debbugs.gnu.org
Subject: bug#22533: Non-determinism in python-3 ".pyc" bytecode
Date: Tue, 02 Feb 2016 21:41:19 +0100

[Message part 1 (text/plain, inline)]

Leo Famulari <leo <at> famulari.name> skribis:

> We fixed this in python-2 with the patch
> python-2.7-source-date-epoch.patch, but I don't know how to write this
> patch for python-3.

I would imagine something like this (untested):

[Message part 2 (text/x-patch, inline)]

--- Python-3.4.3/Lib/importlib/_bootstrap.py	2016-02-02 21:38:48.655809055 +0100
+++ Python-3.4.3/Lib/importlib/_bootstrap.py.new	2016-02-02 21:38:43.659769251 +0100
@@ -667,7 +667,10 @@ def _code_to_bytecode(code, mtime=0, sou
     """Compile a code object into bytecode for writing out to a byte-compiled
     file."""
     data = bytearray(MAGIC_NUMBER)
-    data.extend(_w_long(mtime))
+    if 'SOURCE_DATE_EPOCH' in _os.environ:
+        data.extend(_w_long(string.atoi(_os.environ['SOURCE_DATE_EPOCH'])))
+    else:
+        data.extend(_w_long(mtime))
     data.extend(_w_long(source_size))
     data.extend(marshal.dumps(code))
     return data

[Message part 3 (text/plain, inline)]

Could you give it a try and refine as needed?  :-)

> I asked about this on #debian-reproducible and they said that it wasn't
> an issue for Debian since they don't ship bytecode, but instead generate
> it at install time. Of course, that doesn't really apply to Guix.

I’d recommend trying #reproducible-builds on OFTC, which is more
generic.  Also, in some cases, it’s useful to look at
<git://git.debian.org/git/reproducible/notes.git>, which contains notes
about non-reproducible packages (currently partly Debian-specific, but
we need to lobby to make it more generic.  ;-))

Thanks,
Ludo’.

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