Subject: [bug#43591] [PATCH core-updates] gnu: glibc-final: Catch all cases of a glibc user not requesting 64-bit offsets and then using readdir.

From: Danny Milosavljevic <[email-masked]>
Date: Wed, 30 Sep 2020 00:09:34 +0200

Hi Ludo,

On Tue, 29 Sep 2020 22:52:10 +0200
Ludovic Courtès <[email-masked]> wrote:

> Marius Bakke <[email-masked]> skribis:
> 
> > Arguably running code for foreign architectures through QEMU binfmt is
> > something of a hack.  Mandating that every package *must* be patched to
> > support it seems user-hostile.  I'm more in favor of dropping it on the
> > build farm, or just keep fixing things on a per-package basis.  
> 
> I’m fine with dropping things on the build farm; it’s just about
> modifying machines-for-berlin.scm in maintenance.git.  Any takers?  :-)

I don't know what "dropping things on the build farm" means in this context.
Dropping what exactly?

> The above would override the default CFLAGS in Autoconf-generated
> configure scripts (which is “-O2 -g”).  

That is correct.  I'm currently working on v2 (testing a patchset already)
and I totally forgot to add "-g -O2" the first time around.  Also, glibc
itself must NOT have -D_FILE_OFFSET_BITS=64 (it makes sense not to, too).

>So we’d have to be cautious.
> But I think a global solution is preferable to adding
> -D_FILE_OFFSET_BITS=64 to tens of packages.

I agree.

I still would like to see what actually changes--and I think with
guix-data-services it should actually be possible to compare derivations
before-and-after and find out which derivations of which packages changed
at all because of the global -D_FILE_OFFSET_BITS=64.  I'd like some help
using guix-data-services to find that out.  Otherwise a risk estimation
cannot be done.

Technically, if a package used direct assembly offsets (for some unfathomable
reason), it could have an undetectable problem with the size change of off_t
(and also struct dirent).  So examining the source code of the most essential
packages manually is still good.  That's what I did in
branch wip-file-offsets-64.

I'm in the process of testing a patchset that globally sets

  CFLAGS="-D_FILE_OFFSET_BITS=64 -g -O2"

instead.

That alone is not enough since there are a lot of non-autotools projects that
just ignore the environment variable entirely--not to mention languages other
than C.

I have access to bayfront--but I don't remember how to evaluate a new branch
there  (the new branch is "wip-file-offset-bits-64-sledgehammer").  How does
it work?