Crash compiling my unsafe (crappy) code

[panzi]

I tried to make myself familiar with rust and tried to compile this code with rust 0.7. rustc crashed and gave me this trace.

[jdm]

Could you run rustc under gdb and gist the backtrace from rust_task_fail?

[panzi]

I installed rustc via: ./configure --prefix=$HOME/software/rust && make -j 2 && make install This seems to strip the debug infos. How do I install the debug infos and/or refere gdb to them?

[jdm]

We don't give good debug output yet, but the backtrace will show us mangled functions names which are useful.

[jdm]

Also, seeing if you can reproduce with HEAD would be useful.

[panzi]

Well, when I run gdb --args rustc main.rs I seem not to be able to get a backtrace:

GNU gdb (GDB) Fedora (7.3.50.20110722-16.fc16)
Copyright (C) 2011 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-redhat-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /home/panzi/software/rust/bin/rustc...(no debugging symbols found)...done.
(gdb) run
Starting program: /home/panzi/software/rust/bin/rustc main.rs
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
[New Thread 0x7ffff605b700 (LWP 17992)]
[New Thread 0x7ffff6042700 (LWP 17993)]
[New Thread 0x7ffff4053700 (LWP 17994)]
rust: task failed at 'option::get none', /home/panzi/software/rust-0.7/src/libstd/option.rs:331
error: internal compiler error: unexpected failure
note: the compiler hit an unexpected failure path. this is a bug
note: try running with RUST_LOG=rustc=1,::rt::backtrace to get further details and report the results to github.com/mozilla/rust/issues
rust: task failed at 'explicit failure', /home/panzi/software/rust-0.7/src/librustc/rustc.rs:354
rust: domain main @0x606d90 root task failed
[Thread 0x7ffff605b700 (LWP 17992) exited]
[Thread 0x7ffff4053700 (LWP 17994) exited]
[Thread 0x7ffff6042700 (LWP 17993) exited]
[Inferior 1 (process 17989) exited with code 0145]
(gdb) backtrace
No stack.
(gdb) quit

The program quits. It crashes on a rust level, not a C/C++ level. fail! is called in Option.get which exits the program (no SIGSEGV or anything like this). It's just further proof that this method is a bad idea. But that was already in the output I posted as a gist.

Is there a way to get a stacktrace from a fail!?

[panzi]

Ok I sat a breakpoint at _ZN9rust_task13begin_failureEPKcS1_m and then got this backtrace at that point.

[panzi]

Yeah, middle::trans::common::find_vtable in HEAD looks different: https://github.com/mozilla/rust/blob/master/src/librustc/middle/trans/common.rs#L1091
I guess I compile from git then.

[jdm]

I did mention to get a backtrace from rust_task_fail :) Yours works too, though.

[panzi]

Ok, with git HEAD I had to change my code a bit, but I still get a crash. It's basically the same crash. The only difference is that now then None case is handled and a better fail! message is provided: vtables missing where they are needed

[jdm]

I suspect it might be triggered by one of the destructors. Try commenting them out and see if it's still reproducible?

[panzi]

Indeed. Commenting out the Weakref destructor makes it compile!

[huonw]

That error message is the same as #8059, which is closed as a dupe of #4252; closing this one as a dup too.