[Bug symtab/14441] New: Need to support DW_TAG_rvalue_reference_type

[Bug symtab/14441] New: Need to support DW_TAG_rvalue_reference_type

[dje at google dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=14441

             Bug #: 14441
           Summary: Need to support DW_TAG_rvalue_reference_type
           Product: gdb
           Version: HEAD
            Status: NEW
          Severity: normal
          Priority: P2
         Component: symtab
        AssignedTo: unassigned@sourceware.org
        ReportedBy: dje@google.com
    Classification: Unclassified


llvm has apparently starting emitting this.

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[Bug symtab/14441] Need to support DW_TAG_rvalue_reference_type

[nicholas at mxc dot ca]

http://sourceware.org/bugzilla/show_bug.cgi?id=14441

Nick Lewycky <nicholas at mxc dot ca> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |nlewycky at google dot com

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[Bug symtab/14441] Need to support DW_TAG_rvalue_reference_type

[tromey at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=14441

Tom Tromey <tromey at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tromey at redhat dot com

--- Comment #1 from Tom Tromey <tromey at redhat dot com> 2012-08-08 16:00:47 UTC ---
(In reply to comment #0)
> llvm has apparently starting emitting this.

gcc does too.
IIRC you can see it in libstdc++.so.

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[Bug symtab/14441] Need to support DW_TAG_rvalue_reference_type

[jwakely.gcc at gmail dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=14441

Jonathan Wakely <jwakely.gcc at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jwakely.gcc at gmail dot
                   |                            |com

--- Comment #2 from Jonathan Wakely <jwakely.gcc at gmail dot com> 2012-10-28 13:56:03 UTC ---
Yes G++ trunk emits it, see http://gcc.gnu.org/PR54773

(gdb) ptype x
type = struct X {
  public:
    X & operator=(<unknown type in /dev/shm/a.out, CU 0x0, DIE 0x4b>);
}

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[Bug symtab/14441] Need to support DW_TAG_rvalue_reference_type

[jwakely.gcc at gmail dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=14441

--- Comment #3 from Jonathan Wakely <jwakely.gcc at gmail dot com> 2012-10-28 14:04:54 UTC ---
That link should be http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54773

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[Bug symtab/14441] Need to support DW_TAG_rvalue_reference_type

[emaste at freebsd dot org]

http://sourceware.org/bugzilla/show_bug.cgi?id=14441

emaste at freebsd dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |emaste at freebsd dot org

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[Bug symtab/14441] Need to support DW_TAG_rvalue_reference_type

[jan.kratochvil at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=14441

Jan Kratochvil <jan.kratochvil at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jan.kratochvil at redhat dot com

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[Bug symtab/14441] Need to support DW_TAG_rvalue_reference_type

[jan.kratochvil at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=14441

--- Comment #4 from Jan Kratochvil <jan.kratochvil at redhat dot com> ---
*** Bug 16043 has been marked as a duplicate of this bug. ***

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[Bug symtab/14441] Need to support DW_TAG_rvalue_reference_type

[jan.kratochvil at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=14441

Jan Kratochvil <jan.kratochvil at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at sourceware dot org   |jan.kratochvil at redhat dot com

--- Comment #5 from Jan Kratochvil <jan.kratochvil at redhat dot com> ---
[patch] Support C++11 rvalue (move constructor)
https://sourceware.org/ml/gdb-patches/2013-10/msg00403.html

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[Bug symtab/14441] Need to support DW_TAG_rvalue_reference_type

[jwakely.gcc at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=14441

--- Comment #6 from Jonathan Wakely <jwakely.gcc at gmail dot com> ---
I can live with printing rvalue refs as <unknown type in /dev/shm/a.out, CU
0x0, DIE 0x4b> but the fact you're unable to do anything with them is a much
bigger problem:

struct A { int i; };

int f(A&& a)
{
  return a.i;
}

int main()
{
  return f( A() );
}

Reading symbols from ./a.out...done.
(gdb) start
Temporary breakpoint 1 at 0x4005de: file rv.cc, line 10.
Starting program: /tmp/a.out

Temporary breakpoint 1, main () at rv.cc:10
(gdb) step
f(A&&) (a=<unknown type in /tmp/a.out, CU 0x0, DIE 0x7f>) at rv.cc:5
(gdb) p a.i
Attempt to extract a component of a value that is not a structure.

This makes it almost impossible to debug functions taking rvalues, such as move
constructors and move assignment operators.

And sometimes move constructors are really hard to get right and need to be
debugged (e.g. std::stringstream is giving me major headaches)

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[Bug symtab/14441] Need to support DW_TAG_rvalue_reference_type

[tohava at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=14441

Ori Bar <tohava at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tohava at gmail dot com

--- Comment #7 from Ori Bar <tohava at gmail dot com> ---
A temporary solution for Jontahan's problem is to write:

p ((A*)a)->i;

This becomes messy for more compilcated types

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