[Bug gdb/26828] SIGSEGV in follow_die_offset dwarf2/read.c:22950

["simark at simark dot ca" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=26828

Simon Marchi <simark at simark dot ca> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2020-11-03
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW

--- Comment #7 from Simon Marchi <simark at simark dot ca> ---
I fixed the undefined shift behavior problem, and was able to reproduce your
problem.  This is the command line you provided that I adapted:

../gdb -nx --data-directory=../data-directory -i mi Foo <<EOF
set sysroot /home/simark/build/binutils-gdb/gdb/repo
set osabi GNU/Linux
core-file Foo-core
-stack-list-variables --thread 2 --frame 2 --simple-values
-stack-list-variables --thread 2 --frame 2 --simple-values
-stack-list-variables --thread 2 --frame 2 --simple-values
-stack-list-variables --thread 2 --frame 2 --simple-values
-stack-list-variables --thread 2 --frame 2 --simple-values
-stack-list-variables --thread 2 --frame 2 --simple-values
EOF


This is what I get:

$ ./repo.sh
warning: Found custom handler for signal 7 (Bus error) preinstalled.
warning: Found custom handler for signal 8 (Floating point exception)
preinstalled.
warning: Found custom handler for signal 11 (Segmentation fault) preinstalled.
Some signal dispositions inherited from the environment (SIG_DFL/SIG_IGN)
won't be propagated to spawned programs.
=thread-group-added,id="i1"
~"GNU gdb (GDB) 11.0.50.20201103-git\n"
~"Copyright (C) 2020 Free Software Foundation, Inc.\n"
~"License GPLv3+: GNU GPL version 3 or later
<http://gnu.org/licenses/gpl.html>\nThis is free software: you are free to
change and redistribute it.\nThere is NO WARRANTY, to the extent permitted by
law."
~"\nType \"show copying\" and \"show warranty\" for details.\n"
~"This GDB was configured as \"x86_64-pc-linux-gnu\".\n"
~"Type \"show configuration\" for configuration details.\n"
~"For bug reporting instructions, please see:\n"
~"<https://www.gnu.org/software/gdb/bugs/>.\n"
~"Find the GDB manual and other documentation resources online at:\n   
<http://www.gnu.org/software/gdb/documentation/>."
~"\n\n"
~"For help, type \"help\".\n"
~"Type \"apropos word\" to search for commands related to \"word\"...\n"
~"Reading symbols from Foo...\n"
(gdb) 
&"set sysroot /home/simark/build/binutils-gdb/gdb/repo\n"
=cmd-param-changed,param="sysroot",value="/home/simark/build/binutils-gdb/gdb/repo"
^done
(gdb) 
&"set osabi GNU/Linux\n"
=cmd-param-changed,param="osabi",value="GNU/Linux"
^done
(gdb) 
&"core-file Foo-core\n"
&"warning: Can't open file /media/mmcblk0p1/install/usr/bin/Foo during
file-backed mapping note processing\n"
&"warning: Can't open file /lib/libm-2.21.so during file-backed mapping note
processing\n"
&"warning: Can't open file /lib/libpthread-2.21.so during file-backed mapping
note processing\n"
&"warning: Can't open file /lib/libgcc_s.so.1 during file-backed mapping note
processing\n"
&"warning: Can't open file /media/mmcblk0p1/install/usr/lib/libstdc++.so.6
during file-backed mapping note processing\n"
&"warning: Can't open file /lib/libc-2.21.so during file-backed mapping note
processing\n"
&"warning: Can't open file /lib/ld-2.21.so during file-backed mapping note
processing\n"
=thread-group-started,id="i1",pid="29367"
=thread-created,id="1",group-id="i1"
~"[New LWP 29367]\n"
=thread-created,id="2",group-id="i1"
~"[New LWP 29368]\n"
=library-loaded,id="/lib/libc.so.6",target-name="/lib/libc.so.6",host-name="/lib/libc.so.6",symbols-loaded="0",thread-group="i1",ranges=[{}]
=library-loaded,id="/media/mmcblk0p1/install/usr/bin/../lib/libstdc++.so.6",target-name="/media/mmcblk0p1/install/usr/bin/../lib/libstdc++.so.6",host-name="/media/mmcblk0p1/install/usr/bin/../lib/libstdc++.so.6",symbols-loaded="0",thread-group="i1",ranges=[{}]
=library-loaded,id="/lib/libgcc_s.so.1",target-name="/lib/libgcc_s.so.1",host-name="/lib/libgcc_s.so.1",symbols-loaded="0",thread-group="i1",ranges=[{}]
=library-loaded,id="/lib/libpthread.so.0",target-name="/lib/libpthread.so.0",host-name="/home/simark/build/binutils-gdb/gdb/repo/lib/libpthread.so.0",symbols-loaded="0",thread-group="i1",ranges=[{from="0xb6c30160",to="0xb6c3ec88"}]
=library-loaded,id="/lib/ld-linux.so.3",target-name="/lib/ld-linux.so.3",host-name="/lib/ld-linux.so.3",symbols-loaded="0",thread-group="i1",ranges=[{}]
=library-loaded,id="/lib/libm.so.6",target-name="/lib/libm.so.6",host-name="/lib/libm.so.6",symbols-loaded="0",thread-group="i1",ranges=[{}]
&"warning: Could not load shared library symbols for 5 libraries, e.g.
/lib/libc.so.6.\nUse the \"info sharedlibrary\" command to see the complete
listing.\nDo you need \"set solib-search-path\" or \"set sysroot\"?"
&"\n"
&"warning: Unable to find libthread_db matching inferior's thread library,
thread debugging will not be available.\n"
&"warning: Unable to find libthread_db matching inferior's thread library,
thread debugging will not be available.\n"
~"Core was generated by `./Foo'.\n"
~"Program terminated with signal SIGABRT, Aborted.\n"
~"#0  0xb6c3809c in pthread_cond_wait () from
/home/simark/build/binutils-gdb/gdb/repo/lib/libpthread.so.0\n"
~"[Current thread is 1 (LWP 29367)]\n"
^done
(gdb) 
^done,variables=[{name="lock",arg="1",type="boost::asio::detail::conditionally_enabled_mutex::scoped_lock
&",value="<synthetic pointer>: {<boost::asio::detail::noncopyable> = {<No data
fields>}, mutex_ = @0x2cf50, locked_ =
true}"},{name="this",arg="1",type="boost::asio::detail::conditionally_enabled_event
* const",value="0x2cf70"}]
(gdb) 
^done,variables=[{name="lock",arg="1",type="boost::asio::detail::conditionally_enabled_mutex::scoped_lock
&",value="<synthetic pointer>: {<boost::asio::detail::noncopyable> = {<No data
fields>}, mutex_ = @0x2cf50, locked_ =
true}"},{name="this",arg="1",type="boost::asio::detail::conditionally_enabled_event
* const",value="0x2cf70"}]
(gdb) 
^done,variables=[{name="lock",arg="1",type="boost::asio::detail::conditionally_enabled_mutex::scoped_lock
&",value="<synthetic pointer>: {<boost::asio::detail::noncopyable> = {<No data
fields>}, mutex_ = @0x2cf50, locked_ =
true}"},{name="this",arg="1",type="boost::asio::detail::conditionally_enabled_event
* const",value="0x2cf70"}]
(gdb) 
^done,variables=[{name="lock",arg="1",type="boost::asio::detail::conditionally_enabled_mutex::scoped_lock
&",value="<synthetic pointer>: {<boost::asio::detail::noncopyable> = {<No data
fields>}, mutex_ = @0x2cf50, locked_ =
true}"},{name="this",arg="1",type="boost::asio::detail::conditionally_enabled_event
* const",value="0x2cf70"}]
(gdb) 
^done,variables=[{name="lock",arg="1",type="boost::asio::detail::conditionally_enabled_mutex::scoped_lock
&",value="<synthetic pointer>: {<boost::asio::detail::noncopyable> = {<No data
fields>}, mutex_ = @0x2cf50, locked_ =
true}"},{name="this",arg="1",type="boost::asio::detail::conditionally_enabled_event
* const",value="0x2cf70"}]
(gdb) 
/home/simark/src/binutils-gdb/gdb/dwarf2/read.c:22959:25: runtime error: member
access within null pointer of type 'struct dwarf2_cu'

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