Error in `-zsh': free(): invalid pointer: (emacs, tramp, zsh zle)

[Greg Steuck <greg@xxxxxxx>]

I use zsh 5.5 as my login shell on 4.16.0-amd64 Debian GNU/Linux buster/sid
and also run tramp with GNU Emacs 26.1. In such configuration, this command
causes zsh to fail:

*emacs -q -nw /ssh:localhost:/*

A hard to capture stack trace is quoted at the bottom (I wrapped ssh into a
script with: /usr/bin/ssh "$@" |& tee /tmp/ssh-log). One workaround that
helps is putting this at the top of my .zshrc:

*unsetopt zle*

I was unable to induce the problem outside of emacs/tramp. Simply running
the same ssh command doesn't work, presumably because tramp is opening
extra channels and I didn't have the gumption to figure it out.

The libc version:
lrwxrwxrwx 1 root root 12 Jun 18  2017 /lib/x86_64-linux-gnu/libc.so.6 ->
libc-2.24.so

Trace:
*** Error in `-zsh': free(): invalid pointer: 0x0000555f76936e80 ***
======= Backtrace: =========
/lib/x86_64-linux-gnu/libc.so.6(+0x70bcb)[0x7fd6266efbcb]
/lib/x86_64-linux-gnu/libc.so.6(+0x76f96)[0x7fd6266f5f96]
/lib/x86_64-linux-gnu/libc.so.6(+0x777de)[0x7fd6266f67de]
/usr/lib/x86_64-linux-gnu/zsh/5.5/zsh/zle.so(zrefresh+0x1e98)[0x7fd625e418b8]
/usr/lib/x86_64-linux-gnu/zsh/5.5/zsh/zle.so(zleread+0x492)[0x7fd625e34fe2]
-zsh(zleentry+0xb4)[0x555f754e07a4]
-zsh(+0x51c77)[0x555f754e1c77]
-zsh(+0x4978b)[0x555f754d978b]
-zsh(+0x5b49e)[0x555f754eb49e]
-zsh(parse_event+0x26)[0x555f7550aad6]
-zsh(loop+0x8f)[0x555f754dcfcf]
-zsh(zsh_main+0x49e)[0x555f754e0dde]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf1)[0x7fd62669f2b1]
-zsh(_start+0x2a)[0x555f754a772a]
======= Memory map: ========
555f75490000-555f75556000 r-xp 00000000 fe:01 34603163
 /bin/zsh
555f75755000-555f75757000 r--p 000c5000 fe:01 34603163
 /bin/zsh
555f75757000-555f7575d000 rw-p 000c7000 fe:01 34603163
 /bin/zsh
555f7575d000-555f75771000 rw-p 00000000 00:00 0
555f76900000-555f76a7d000 rw-p 00000000 00:00 0
[heap]
7fd620000000-7fd620021000 rw-p 00000000 00:00 0
7fd620021000-7fd624000000 ---p 00000000 00:00 0
7fd625199000-7fd6251b0000 r-xp 00000000 fe:01 525849
 /lib/x86_64-linux-gnu/libgcc_s.so.1
7fd6251b0000-7fd6253af000 ---p 00017000 fe:01 525849
 /lib/x86_64-linux-gnu/libgcc_s.so.1
7fd6253af000-7fd6253b0000 r--p 00016000 fe:01 525849
 /lib/x86_64-linux-gnu/libgcc_s.so.1
7fd6253b0000-7fd6253b1000 rw-p 00017000 fe:01 525849
 /lib/x86_64-linux-gnu/libgcc_s.so.1
7fd6253b1000-7fd6253b3000 r-xp 00000000 fe:01 1969149
/usr/lib/x86_64-linux-gnu/zsh/5.5/zsh/regex.so
7fd6253b3000-7fd6255b2000 ---p 00002000 fe:01 1969149
/usr/lib/x86_64-linux-gnu/zsh/5.5/zsh/regex.so
7fd6255b2000-7fd6255b3000 r--p 00001000 fe:01 1969149
/usr/lib/x86_64-linux-gnu/zsh/5.5/zsh/regex.so
7fd6255b3000-7fd6255b4000 rw-p 00002000 fe:01 1969149
/usr/lib/x86_64-linux-gnu/zsh/5.5/zsh/regex.so
7fd6255b4000-7fd6255d6000 r--s 00000000 fe:01 5376916
/usr/share/zsh/functions/Completion/Base.zwc
7fd6255d6000-7fd6255d9000 r-xp 00000000 fe:01 1969181
/usr/lib/x86_64-linux-gnu/zsh/5.5/zsh/stat.so
7fd6255d9000-7fd6257d8000 ---p 00003000 fe:01 1969181
/usr/lib/x86_64-linux-gnu/zsh/5.5/zsh/stat.so
7fd6257d8000-7fd6257d9000 r--p 00002000 fe:01 1969181
/usr/lib/x86_64-linux-gnu/zsh/5.5/zsh/stat.so
7fd6257d9000-7fd6257da000 rw-p 00003000 fe:01 1969181
/usr/lib/x86_64-linux-gnu/zsh/5.5/zsh/stat.so
7fd6257da000-7fd6257e4000 r-xp 00000000 fe:01 1969174
/usr/lib/x86_64-linux-gnu/zsh/5.5/zsh/parameter.so
7fd6257e4000-7fd6259e3000 ---p 0000a000 fe:01 1969174
/usr/lib/x86_64-linux-gnu/zsh/5.5/zsh/parameter.so
7fd6259e3000-7fd6259e4000 r--p 00009000 fe:01 1969174
/usr/lib/x86_64-linux-gnu/zsh/5.5/zsh/parameter.so
7fd6259e4000-7fd6259e5000 rw-p 0000a000 fe:01 1969174
/usr/lib/x86_64-linux-gnu/zsh/5.5/zsh/parameter.so
7fd6259e5000-7fd6259ed000 r-xp 00000000 fe:01 1969173
/usr/lib/x86_64-linux-gnu/zsh/5.5/zsh/zutil.so
7fd6259ed000-7fd625bec000 ---p 00008000 fe:01 1969173
/usr/lib/x86_64-linux-gnu/zsh/5.5/zsh/zutil.so
7fd625bec000-7fd625bed000 r--p 00007000 fe:01 1969173
/usr/lib/x86_64-linux-gnu/zsh/5.5/zsh/zutil.so
7fd625bed000-7fd625bee000 rw-p 00008000 fe:01 1969173
/usr/lib/x86_64-linux-gnu/zsh/5.5/zsh/zutil.so
7fd625bee000-7fd625c11000 r-xp 00000000 fe:01 1969161
/usr/lib/x86_64-linux-gnu/zsh/5.5/zsh/complete.so
7fd625c11000-7fd625e10000 ---p 00023000 fe:01 1969161
/usr/lib/x86_64-linux-gnu/zsh/5.5/zsh/complete.so
7fd625e10000-7fd625e12000 r--p 00022000 fe:01 1969161
/usr/lib/x86_64-linux-gnu/zsh/5.5/zsh/complete.so
7fd625e12000-7fd625e13000 rw-p 00024000 fe:01 1969161
/usr/lib/x86_64-linux-gnu/zsh/5.5/zsh/complete.so
7fd625e13000-7fd625e5b000 r-xp 00000000 fe:01 1969164
/usr/lib/x86_64-linux-gnu/zsh/5.5/zsh/zle.so
7fd625e5b000-7fd62605b000 ---p 00048000 fe:01 1969164
/usr/lib/x86_64-linux-gnu/zsh/5.5/zsh/zle.so
7fd62605b000-7fd62605d000 r--p 00048000 fe:01 1969164
/usr/lib/x86_64-linux-gnu/zsh/5.5/zsh/zle.so
7fd62605d000-7fd626064000 rw-p 0004a000 fe:01 1969164
/usr/lib/x86_64-linux-gnu/zsh/5.5/zsh/zle.so
7fd626064000-7fd626065000 rw-p 00000000 00:00 0
7fd626065000-7fd626067000 r-xp 00000000 fe:01 1969148
/usr/lib/x86_64-linux-gnu/zsh/5.5/zsh/terminfo.so
7fd626067000-7fd626266000 ---p 00002000 fe:01 1969148
/usr/lib/x86_64-linux-gnu/zsh/5.5/zsh/terminfo.so
7fd626266000-7fd626267000 r--p 00001000 fe:01 1969148
/usr/lib/x86_64-linux-gnu/zsh/5.5/zsh/terminfo.so
7fd626267000-7fd626268000 rw-p 00002000 fe:01 1969148
/usr/lib/x86_64-linux-gnu/zsh/5.5/zsh/terminfo.so
7fd626268000-7fd62626b000 r-xp 00000000 fe:01 1840644
/usr/lib/x86_64-linux-gnu/libnss_cache.so.2.0
7fd62626b000-7fd62646b000 ---p 00003000 fe:01 1840644
/usr/lib/x86_64-linux-gnu/libnss_cache.so.2.0
7fd62646b000-7fd62646c000 r--p 00003000 fe:01 1840644
/usr/lib/x86_64-linux-gnu/libnss_cache.so.2.0
7fd62646c000-7fd62646d000 rw-p 00004000 fe:01 1840644
/usr/lib/x86_64-linux-gnu/libnss_cache.so.2.0
7fd62646d000-7fd626477000 r-xp 00000000 fe:01 525882
 /lib/x86_64-linux-gnu/libnss_files-2.24.so
7fd626477000-7fd626677000 ---p 0000a000 fe:01 525882
 /lib/x86_64-linux-gnu/libnss_files-2.24.so
7fd626677000-7fd626678000 r--p 0000a000 fe:01 525882
 /lib/x86_64-linux-gnu/libnss_files-2.24.so
7fd626678000-7fd626679000 rw-p 0000b000 fe:01 525882
 /lib/x86_64-linux-gnu/libnss_files-2.24.so
7fd626679000-7fd62667f000 rw-p 00000000 00:00 0
7fd62667f000-7fd626814000 r-xp 00000000 fe:01 526032
 /lib/x86_64-linux-gnu/libc-2.24.so
7fd626814000-7fd626a14000 ---p 00195000 fe:01 526032
 /lib/x86_64-linux-gnu/libc-2.24.so
7fd626a14000-7fd626a18000 r--p 00195000 fe:01 526032
 /lib/x86_64-linux-gnu/libc-2.24.so
7fd626a18000-7fd626a1a000 rw-p 00199000 fe:01 526032
 /lib/x86_64-linux-gnu/libc-2.24.so
7fd626a1a000-7fd626a1e000 rw-p 00000000 00:00 0
7fd626a1e000-7fd626b21000 r-xp 00000000 fe:01 525858
 /lib/x86_64-linux-gnu/libm-2.24.so
7fd626b21000-7fd626d20000 ---p 00103000 fe:01 525858
 /lib/x86_64-linux-gnu/libm-2.24.so
7fd626d20000-7fd626d21000 r--p 00102000 fe:01 525858
 /lib/x86_64-linux-gnu/libm-2.24.so
7fd626d21000-7fd626d22000 rw-p 00103000 fe:01 525858
 /lib/x86_64-linux-gnu/libm-2.24.so
7fd626d22000-7fd626d48000 r-xp 00000000 fe:01 526021
 /lib/x86_64-linux-gnu/libtinfo.so.5.9
7fd626d48000-7fd626f47000 ---p 00026000 fe:01 526021
 /lib/x86_64-linux-gnu/libtinfo.so.5.9
7fd626f47000-7fd626f4b000 r--p 00025000 fe:01 526021
 /lib/x86_64-linux-gnu/libtinfo.so.5.9
7fd626f4b000-7fd626f4c000 rw-p 00029000 fe:01 526021
 /lib/x86_64-linux-gnu/libtinfo.so.5.9
7fd626f4c000-7fd626f4f000 r-xp 00000000 fe:01 525881
 /lib/x86_64-linux-gnu/libdl-2.24.so
7fd626f4f000-7fd62714e000 ---p 00003000 fe:01 525881
 /lib/x86_64-linux-gnu/libdl-2.24.so
7fd62714e000-7fd62714f000 r--p 00002000 fe:01 525881
 /lib/x86_64-linux-gnu/libdl-2.24.so
7fd62714f000-7fd627150000 rw-p 00003000 fe:01 525881
 /lib/x86_64-linux-gnu/libdl-2.24.so
7fd627150000-7fd627154000 r-xp 00000000 fe:01 525897
 /lib/x86_64-linux-gnu/libcap.so.2.25
7fd627154000-7fd627354000 ---p 00004000 fe:01 525897
 /lib/x86_64-linux-gnu/libcap.so.2.25
7fd627354000-7fd627355000 r--p 00004000 fe:01 525897
 /lib/x86_64-linux-gnu/libcap.so.2.25
7fd627355000-7fd627356000 rw-p 00005000 fe:01 525897
 /lib/x86_64-linux-gnu/libcap.so.2.25
7fd627356000-7fd627379000 r-xp 00000000 fe:01 525998
 /lib/x86_64-linux-gnu/ld-2.24.so
7fd62739f000-7fd6273b6000 r--s 00000000 fe:01 5376796
/usr/share/zsh/functions/Completion.zwc
7fd6273b6000-7fd627551000 r--p 00000000 fe:01 1183733
/usr/lib/locale/locale-archive
7fd627551000-7fd627553000 rw-p 00000000 00:00 0
7fd62756a000-7fd62756b000 rw-p 00000000 00:00 0
7fd62756b000-7fd627572000 r--s 00000000 fe:01 1967657
/usr/lib/x86_64-linux-gnu/gconv/gconv-modules.cache
7fd627572000-7fd627579000 rw-p 00000000 00:00 0
7fd627579000-7fd62757a000 r--p 00023000 fe:01 525998
 /lib/x86_64-linux-gnu/ld-2.24.so
7fd62757a000-7fd62757b000 rw-p 00024000 fe:01 525998
 /lib/x86_64-linux-gnu/ld-2.24.so
7fd62757b000-7fd62757c000 rw-p 00000000 00:00 0
7ffeddb69000-7ffeddb8a000 rw-p 00000000 00:00 0
[stack]
7ffeddbd0000-7ffeddbd3000 r--p 00000000 00:00 0
[vvar]
7ffeddbd3000-7ffeddbd5000 r-xp 00000000 00:00 0
[vdso]