Hi,

This bug report is to keep track of the discussions around libfaketime
for i686-linux.  Right now, libfaketime segfaults when used to run the
test suite of ‘nss’ on i686-linux.  This can be reproduced in a simple
way as of ‘core-updates’ commit
05e6bd3efe1b03190839d2b91b09fa768c4ef83c:

--8<---------------cut here---------------start------------->8---
$ ./pre-inst-env guix shell -s i686-linux libfaketime bash -- \
     faketime 2023-01-01 bash -c true
Caught Segmentation fault
--8<---------------cut here---------------end--------------->8---

Commit 127f1842fb037cc5acfc5406e373ccd723127732 (“gnu: libfaketime:
Support compilation with glibc 2.39 on i686-linux.”) was written under
the assumption that packages in Guix would be built with
‘_TIME_BITS=64’.

Alas, as Z572 found out, packages that use Gnulib are typically built
that way, but other packages, such as ‘nss’ and ‘bash’, are often built
with a 32-bit ‘time_t’.  Our modified libfaketime fails badly in these
cases.

The libfaketime limitations are discussed in
<https://github.com/wolfcw/libfaketime/issues/418>.

OTOH, datefudge explicitly provides replacements for both the 32-bit and
64-bit variants of the relevant libc symbols on 32-bit platforms.  It
seems to work fine with 32-bit time_t programs (like ‘bash’) and 64-bit
time_t programs (like ‘date’ from Coreutils):

--8<---------------cut here---------------start------------->8---
$ ./pre-inst-env guix shell -s i686-linux datefudge bash coreutils -- datefudge 2023-01-01 bash -c true
$ ./pre-inst-env guix shell -s i686-linux datefudge bash coreutils -- datefudge 2023-01-01 date
Sun Jan  1 00:00:00 CET 2023
--8<---------------cut here---------------end--------------->8---

So the easiest short-term solution seems to be using datefudge to run
the ‘nss’ tests on 32-bit platforms, as Chris already suggested before
(patch below; it’s being built right now, I’ll see tomorrow if it
worked…).

Longer-term, as discussed with Z572, we should set up a branch where
we’d ensure “everything” uses 64-bit ‘time_t’ on 32-bit platforms
(that’s beyond the scope of this issue though).

Ludo’.