port-arm/56239: lib/libc/regex/t_exhaust:regcomp_too_big test fails on aarch64

[gson%gson.org@localhost (Andreas Gustafsson)]

>Number:         56239
>Category:       port-arm
>Synopsis:       lib/libc/regex/t_exhaust:regcomp_too_big test fails on aarch64
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-arm-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Jun 07 07:40:00 +0000 2021
>Originator:     Andreas Gustafsson
>Release:        NetBSD-current, source date >= 2021.02.23.22.14.59
>Organization:

>Environment:
System: NetBSD
Architecture: aarch64
Machine: evbarm
>Description:

The regcomp_too_big test case of the lib/libc/regex/t_exhaust test
program is currently failing on multiple testbeds.   It usually fails
like this:

  lib/libc/regex/t_exhaust (221/890): 1 test cases
      regcomp_too_big: [5.293623s] Failed: /tmp/build/2021.02.23.22.14.59-evbarm-aarch64/src/tests/lib/libc/regex/t_exhaust.c:72: p != NULL not met

but occasionally like this:

  lib/libc/regex/t_exhaust (221/891): 1 test cases
      regcomp_too_big: [ 6537.6276466] UVM: pid 17844 (t_exhaust), uid 0 killed: out of swap
  [46.502225s] Failed: Test program received signal 9

and occasionally it passes.

This happens on:

 - the TNF testbed (qemu, 512 MB virtual RAM)
 - My testbed (qemu, 1 GB virtual RAM)
 - martin's testbed (real hardware, 3 GB RAM)

The problem started with this commit:

  2021.02.23.22.14.59 christos src/lib/libc/regex/Attic/cclass.h 1.8
  2021.02.23.22.14.59 christos src/lib/libc/regex/cname.h 1.8
  2021.02.23.22.14.59 christos src/lib/libc/regex/engine.c 1.25
  2021.02.23.22.14.59 christos src/lib/libc/regex/re_format.7 1.13
  2021.02.23.22.14.59 christos src/lib/libc/regex/regcomp.c 1.39
  2021.02.23.22.14.59 christos src/lib/libc/regex/regerror.c 1.24
  2021.02.23.22.14.59 christos src/lib/libc/regex/regex.3 1.27
  2021.02.23.22.14.59 christos src/lib/libc/regex/regex2.h 1.14
  2021.02.23.22.14.59 christos src/lib/libc/regex/regexec.c 1.23
  2021.02.23.22.14.59 christos src/lib/libc/regex/regfree.c 1.16
  2021.02.23.22.14.59 christos src/lib/libc/regex/utils.h 1.7

Logs:

  https://www.gson.org/netbsd/bugs/build/evbarm-aarch64/commits-2021.02.html#2021.02.23.22.14.59

  http://www.netbsd.org/~martin/aarch64-atf/47_atf.html#lib_libc_regex_t_exhaust_regcomp_too_big

Additional logs (less helpful because of unrelated panics):

  http://releng.netbsd.org/b5reports/evbarm-aarch64/commits-2021.02.html#2021.02.23.22.14.59

>How-To-Repeat:

Run the ATF tests on NetBSD/evbarm-aarch64.

>Fix: