lib/54061: regcomp_too_big test cases now fail on amd64

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

>Number:         54061
>Category:       lib
>Synopsis:       regcomp_too_big test cases now fail on amd64
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    lib-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Mar 15 13:35:00 +0000 2019
>Originator:     Andreas Gustafsson
>Release:        NetBSD-current
>Organization:

>Environment:
System: NetBSD
Architecture: x86_64
Machine: amd64
>Description:

The following two test cases are failing on amd64, but not on i386:

  lib/libc/regex/t_exhaust:regcomp_too_big
  lib/libtre/t_exhaust:regcomp_too_big

Log output:

  http://releng.netbsd.org/b5reports/amd64/2019/2019.03.08.20.35.10/test.html#lib_libtre_t_exhaust_regcomp_too_big
  http://www.gson.org/netbsd/bugs/build/amd64-baremetal/2019/2019.03.14.19.51.49/test.html#lib_libtre_t_exhaust_regcomp_too_big

The above links are for the same test case, but from different machines
and source dates, and the latter one contains a backtrace:

  <jemalloc>: Lock rank order reversal: extent_mutex_pool(16) extent_avail(15)
  Test program crashed; attempting to get stack trace
  [New process 1]
  Core was generated by `t_exhaust'.
  Program terminated with signal SIGABRT, Aborted.
  #0  0x000071b62c7996fa in _lwp_kill () from /usr/lib/libc.so.12
  #0  0x000071b62c7996fa in _lwp_kill () from /usr/lib/libc.so.12
  #1  0x000071b62c7993a9 in abort () from /usr/lib/libc.so.12
  #2  0x000071b62c6bac0a in ?? () from /usr/lib/libc.so.12
  #3  0x000071b62c6eac19 in ?? () from /usr/lib/libc.so.12
  #4  0x000071b62c6ed820 in extent_dalloc () from /usr/lib/libc.so.12
  #5  0x000071b62c6f33a3 in extent_alloc_wrapper () from /usr/lib/libc.so.12
  #6  0x000071b62c7229c3 in ?? () from /usr/lib/libc.so.12
  #7  0x000071b62c724d1d in arena_tcache_fill_small () from /usr/lib/libc.so.12
  #8  0x000071b62c6bc81b in tcache_alloc_small_hard () from /usr/lib/libc.so.12
  #9  0x000071b62c730e2f in ?? () from /usr/lib/libc.so.12
  #10 0x000071b62c731bf7 in malloc () from /usr/lib/libc.so.12
  #11 0x000071b62d2026ab in tre_stack_new () from /usr/lib/libtre.so.0
  #12 0x000071b62d20bb25 in tre_compile () from /usr/lib/libtre.so.0
  #13 0x000071b62d20d9ff in tre_regncomp () from /usr/lib/libtre.so.0
  #14 0x00000001ecc011ee in atfu_regcomp_too_big_body ()
  #15 0x000071b62ce09bdc in atf_tc_run () from /usr/lib/libatf-c.so.0
  #16 0x000071b62ce06c5d in atf_tp_main () from /usr/lib/libatf-c.so.0
  #17 0x00000001ecc0105d in ___start ()
  #18 0x00007f7ef3002c9e in dlclose () from /usr/libexec/ld.elf_so
  #19 0x00007f7ffff03324 in ?? ()
  #20 0x00007f7ffff0333f in ?? ()
  #21 0x0000000000000000 in ?? ()
  Stack trace complete

They started failing some time between source date 2019.03.07.18.32.10 and
2019.03.08.20.35.10.  A bisection is in progress to narrow this down further.

>How-To-Repeat:

>Fix: