[llvm-dev] Ubuntu APT, lldb crash, fix suggestion

[Dylan McKay via llvm-dev]

Such a patch would be very welcome. Just open up a diff on Phabricator and
it should be reviewed and merged pretty quick.
On 15 Nov 2015 06:39, "Eugene Kosov via llvm-dev" <llvm-dev at lists.llvm.org>
wrote:

> Hello.
>
> I use these packages http://llvm.org/apt/
>
> llldb doesn't work. It crashes on start with the following backtrace.
>
> #0  0x00007ffff475f8f9 in llvm::cl::Option::addArgument() () from
> /usr/lib/x86_64-linux-gnu/libLLVM-3.8.so.1
> #1  0x00007fffee3787af in global constructors keyed to a () from
> /usr/local/lib/python2.7/dist-packages/lldb/_lldb.so
> #2  0x00007fffefc6e020 in __frame_dummy_init_array_entry () from
> /usr/local/lib/python2.7/dist-packages/lldb/_lldb.so
> #3  0x00007fffffffdec8 in ?? ()
> #4  0x00007fffffffded8 in ?? ()
> #5  0x00007fffefc6e258 in __frame_dummy_init_array_entry ()
> #6  0x0000000000000000 in ?? ()
>
> Dump of assembler code for function _ZN4llvm2cl6Option11addArgumentEv:
>    0x00007ffff475f8b0 <+0>:     push   %r15
>    0x00007ffff475f8b2 <+2>:     push   %r14
>    0x00007ffff475f8b4 <+4>:     push   %r13
>    0x00007ffff475f8b6 <+6>:     push   %r12
>    0x00007ffff475f8b8 <+8>:     push   %rbp
>    0x00007ffff475f8b9 <+9>:     push   %rbx
>    0x00007ffff475f8ba <+10>:    mov    %rdi,%rbx
>    0x00007ffff475f8bd <+13>:    sub    $0x58,%rsp
>    0x00007ffff475f8c1 <+17>:    mov    0xe64818(%rip),%rbp        #
> 0x7ffff55c40e0
>    0x00007ffff475f8c8 <+24>:    mov    %fs:0x28,%rax
>    0x00007ffff475f8d1 <+33>:    mov    %rax,0x48(%rsp)
>    0x00007ffff475f8d6 <+38>:    xor    %eax,%eax
>    0x00007ffff475f8d8 <+40>:    callq  0x7ffff47a1740
> <_ZN4llvm21llvm_is_multithreadedEv>
>    0x00007ffff475f8dd <+45>:    test   %al,%al
>    0x00007ffff475f8df <+47>:    jne    0x7ffff475fac0
> <_ZN4llvm2cl6Option11addArgumentEv+528>
>    0x00007ffff475f8e5 <+53>:    test   %rbp,%rbp
>    0x00007ffff475f8e8 <+56>:    je     0x7ffff475face
> <_ZN4llvm2cl6Option11addArgumentEv+542>
>    0x00007ffff475f8ee <+62>:    mov    0x18(%rbx),%r12
>    0x00007ffff475f8f2 <+66>:    mov    0xe647e7(%rip),%rbp        #
> 0x7ffff55c40e0
> => 0x00007ffff475f8f9 <+73>:    cmpb   $0x0,(%r12)
>    0x00007ffff475f8fe <+78>:    jne    0x7ffff475f968
> <_ZN4llvm2cl6Option11addArgumentEv+184>
>    0x00007ffff475f900 <+80>:    xor    %r12d,%r12d
>    0x00007ffff475f903 <+83>:    movzwl 0xc(%rbx),%eax
>    0x00007ffff475f907 <+87>:    shr    $0x7,%ax
>    0x00007ffff475f90b <+91>:    and    $0x3,%eax
>    0x00007ffff475f90e <+94>:    cmp    $0x1,%eax
>    0x00007ffff475f911 <+97>:    je     0x7ffff475fc10
> <_ZN4llvm2cl6Option11addArgumentEv+864>
>    0x00007ffff475f917 <+103>:   testb  $0x8,0xd(%rbx)
>    0x00007ffff475f91b <+107>:   jne    0x7ffff475faf0
> <_ZN4llvm2cl6Option11addArgumentEv+576>
>    0x00007ffff475f921 <+113>:   movzbl 0xc(%rbx),%eax
>    0x00007ffff475f925 <+117>:   and    $0x7,%eax
>    0x00007ffff475f928 <+120>:   cmp    $0x4,%eax
>    0x00007ffff475f92b <+123>:   je     0x7ffff475fba0
> <_ZN4llvm2cl6Option11addArgumentEv+752>
>    0x00007ffff475f931 <+129>:   test   %r12b,%r12b
>    0x00007ffff475f934 <+132>:   jne    0x7ffff475fcdb
> <_ZN4llvm2cl6Option11addArgumentEv+1067>
>    0x00007ffff475f93a <+138>:   mov    0x48(%rsp),%rax
>    0x00007ffff475f93f <+143>:   xor    %fs:0x28,%rax
>    0x00007ffff475f948 <+152>:   movb   $0x1,0x38(%rbx)
>    0x00007ffff475f94c <+156>:   jne    0x7ffff475fcd6
> <_ZN4llvm2cl6Option11addArgumentEv+1062>
>    0x00007ffff475f952 <+162>:   add    $0x58,%rsp
>    0x00007ffff475f956 <+166>:   pop    %rbx
>    0x00007ffff475f957 <+167>:   pop    %rbp
>    0x00007ffff475f958 <+168>:   pop    %r12
>    0x00007ffff475f95a <+170>:   pop    %r13
>    0x00007ffff475f95c <+172>:   pop    %r14
>    0x00007ffff475f95e <+174>:   pop    %r15
>
> We have a null pointer dereference here.
>
> (gdb) p $r12
> $1 = 0
>
> Here is that line of code
> https://github.com/llvm-mirror/llvm/blob/master/lib/Support/CommandLine.cpp#L123
>
> Somehow ArgStr is a nullptr.
>
> I suggest to change ArgStr type to StringRef to fix my crash. Also, that
> will modernize code. I can provide a patch. Additionally, I can also change
> some other const char * types to StringRef where appropriate. Will such
> patch be accepted? Do I need to fill a ticket in bug tracker?
>
> --
> Eugene
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20151115/06c7853d/attachment.html>