Re: Lua shared object asymmetry loading Xlib.

[Valery Ushakov <uwe%stderr.spb.ru@localhost>]

On Wed, Dec 26, 2018 at 09:44:53 -0900, Phil Rulon wrote:

> msd$ /usr/bin/lua -v test.lua
> Lua 5.3.3  Copyright (C) 1994-2016 Lua.org, PUC-Rio
> table
> function
> [1]   Segmentation fault (core dumped) /usr/bin/lua -v test.lua
> 
> msd$ gdb -q /usr/bin/lua lua.core
> Reading symbols from /usr/bin/lua...(no debugging symbols found)...done.
> [New process 1]
> Core was generated by `lua'.
> Program terminated with signal SIGSEGV, Segmentation fault.
> #0  0x00007f7ff5001458 in ?? ()
> (gdb) where
> #0  0x00007f7ff5001458 in ?? ()
> #1  0x00007f7ff64f3d69 in __cxa_finalize () from /usr/lib/libc.so.12
> #2  0x00007f7ff64f3a4a in exit () from /usr/lib/libc.so.12
> #3  0x000000000040176c in ___start ()

This is because atexit and dlopen don't mix too well:

#0  0x00007f7ff68f1388 in atexit () from /usr/lib/libc.so.12
#1  0x00007f7ff540147d in XauFileName () from /usr/X11R7/lib/libXau.so.7
#2  0x00007f7ff54010b7 in XauGetBestAuthByAddr ()
   from /usr/X11R7/lib/libXau.so.7
#3  0x00007f7ff5c0bd5b in ?? () from /usr/X11R7/lib/libxcb.so.2
#4  0x00007f7ff5c0bf0d in _xcb_get_auth_info () from /usr/X11R7/lib/libxcb.so.2
#5  0x00007f7ff5c0bb8e in xcb_connect_to_display_with_auth_info ()
   from /usr/X11R7/lib/libxcb.so.2
#6  0x00007f7ff606323d in _XConnectXCB () from /usr/X11R7/lib/libX11.so.7
#7  0x00007f7ff6061f81 in XOpenDisplay () from /usr/X11R7/lib/libX11.so.7
#8  0x00007f7ff6400692 in open_display (L=0x7f7ff7b01808) at Xlib.c:8


When atexit handlers are run when main returns the dlclose has already
yanked the function that was registered to run.  With explicit
os.exit() the exit happens while the libs are still loaded, so it
works ok.


> msd$ /usr/pkg/bin/lua5.3 -v test.lua
> Lua 5.3.4  Copyright (C) 1994-2017 Lua.org, PUC-Rio
> boolean
> /usr/pkg/bin/lua5.3: test.lua:4: attempt to index a boolean value (local
> 'Xlib')
> stack traceback:
>         test.lua:4: in main chunk
>         [C]: in ?

I can't reproduce this second problem on current.

-uwe