gptboot broken when compiled with clang 6 and WITHOUT_LOADER_GELI -- clang 5 is OK

[Dimitry Andric]

On 26 Apr 2018, at 06:17, Dewayne Geraghty <dewayne.geraghty at heuristicsystems.com.au> wrote:
> 
> Andre, You're not alone.  I think there's a problem with clang6 on i386
> FreeBSD 11.1X, refer:
> https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=227552
> https://forums.freebsd.org/threads/uptime-w-i386-breakage.65584/
> and perhaps also on amd64, search for
> https://bugs.freebsd.org/bugzilla/buglist.cgi?quicksearch=clang&list_id=226390.
> 
> Without time to investigate I've reverted userland
> FreeBSD 11.2-PRERELEASE  r332843M    amd64 1101515 1101509
> FreeBSD 11.2-PRERELEASE  r332843M    i386 1101515 1101509

As noted in another post, I cannot reproduce the problems with gptboot,
but with FreeBSD-11.2-PRERELEASE-i386-20180420-r332802, I do indeed see
w and uptime crashing in libxo:

(gdb) bt
#0  ifree (tsd=0x28000000) at arena.h:799
#1  0x2814b506 in __free (ptr=0x280601ef) at tsd.h:716
#2  0x2808bb07 in xo_do_emit_fields () at /usr/src/contrib/libxo/libxo/libxo.c:6419
#3  0x28089a1c in xo_do_emit (xop=<value optimized out>, flags=<value optimized out>, fmt=0x804ad4d "{:time-of-day/%s} ") at /usr/src/contrib/libxo/libxo/libxo.c:6470
#4  0x28089b61 in xo_emit (fmt=0x804ad4d "{:time-of-day/%s} ") at /usr/src/contrib/libxo/libxo/libxo.c:6541
#5  0x08049f50 in main (argc=<value optimized out>, argv=<value optimized out>) at /usr/src/usr.bin/w/w.c:475
#6  0x080494cd in _start1 ()
#7  0x08049448 in _start ()
#8  0x00000000 in ?? ()

Not sure if this has anything to do with clang though, it looks more
like a double free to me, at first glance.  I'll do some debugging.

-Dimitry

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