Re: Build failure for Emacs master

[Andy Moreton]

On Wed 13 Apr 2016, Eli Zaretskii wrote:

>> From: Andy Moreton <address@hidden>
>> Date: Tue, 12 Apr 2016 22:49:32 +0100
>> 
>> As another data point, I have a similar failure from the emacs-25 branch
>> building with MSYS2 64bit on Win7.
>> 
>> On that machine, building with "make -j4" fails and produces a corrupted
>> loaddefs.el. Deleting loaddefs.el and rebuilding with "make -j4" also
>> fails. Deleting loaddefs.el and rebuilding with "make -j1" succeeds.
>
> Please debug the corruption.  I don't see the problem on any of my
> builds, so I cannot debug this, and having all these reports without
> anyone working on fixing the problem is very disturbing.

The corrupted loaddefs.el file seems to be the right size, but the last
768 bytes are zero instead of the expected content.

To debug this I have tried extracting the command from the autoload target
in lisp/Makefile and running that standalone. This results in repeatably
building a corrutp loaddefs.el (if it is deleted before each run).

Running that command using "bootstrap-emacs -Q" (i.e. interactively)
shows that the *autoload-file* buffer contains the 768 zero characters
at end, so it appears that the corruption occurs before the buffer is
written to disk.

Any hints on how to debug `batch-update-autoloads' to diagnose this
further would be welcome.

    AndyM