2.4-2.5 x64: bash crashes on backticks, gdb crashes on opening core dump

Ivan Pozdeev vano@mail.mipt.ru
Sun Mar 20 08:46:00 GMT 2016


bash
----
I'm being plagued by these crashes for about half a month now.
Specifically, it cannot run any `configure' script.
The crashes appear to happen in child bash/sh processes launched while 
processing backticks. Other times, commands with stream redirection fail 
silently or produce nothing. Simple commands or very short scripts do 
not fail.

On trying to open `sh.exe.core', gdb 1.10 crashes, too; gdb 1.9 says 
"get_core_register_section: Assertion `core_vec' failed" (see 
attachment). So I'm unable to diagnose bash's problem right now.

At another machine with the same packages, bash does not fail, but gdb's 
problem stands. Already tried reinstalling all the packages `bash' 
depends on and itself to no effect.

gdb
---
I managed to debug the gdb session with VisualGDB (trial).
It turns out, the root cause is that the /bin/sh executable is x64, but 
the core file `sh.exe.core' - of the same executable - has i386 format!
(objdump: <...>sh.exe.core:     file format elf32-i386)

And gdb doesn't check that. Created ticket (incl. patch):
https://sourceware.org/bugzilla/show_bug.cgi?id=19834

Now I'm stumped. How can this be?! Does this mean `dumper' is faulty?
If this was normal, gdb would likely be able to process the dumps.

further action
--------------
Since the crash dump is unusable, I'm now going the only way available, 
checking `dumper''s workings (this needs to be done anyway)

summary
-------
Writing this primarily to alert the community of these apparent critical 
bugs.
Hints on where to look inside `dumper' would be more than welcome, too.

--
Regards,
Ivan Pozdeev






-------------- next part --------------
$ gdb /bin/sh UU/sh.exe.core
GNU gdb (GDB) Cygwin 7.9.1-1
Copyright (C) 2015 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-pc-cygwin".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from /bin/sh...(no debugging symbols found)...done.

warning: core file may not match specified executable file.
[New Thread 0x1288]
[New Thread 0x2f38]
/wip/cygport-git/gdb/gdb-7.9.1-1.x86_64/src/gdb-7.9.1/gdb/corelow.c:542: internal-error: get_core_register_section: Assertion `core_vec' failed.
A problem internal to GDB has been detected,
further debugging may prove unreliable.
Quit this debugging session? (y or n) y

This is a bug, please report it.  For instructions, see:
<http://www.gnu.org/software/gdb/bugs/>.

/wip/cygport-git/gdb/gdb-7.9.1-1.x86_64/src/gdb-7.9.1/gdb/corelow.c:542: internal-error: get_core_register_section: Assertion `core_vec' failed.
A problem internal to GDB has been detected,
further debugging may prove unreliable.
Create a core file of GDB? (y or n) y
*** starting debugger for pid 6248, tid 9044
*** continuing pid 6248 from debugger call (1)
Aborted (core dumped)
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