[Bug gdb/29865] New: The GDB dies during unwind the stack - question

[Bug gdb/29865] New: The GDB dies during unwind the stack - question

[filip.bascarevic at siemens dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=29865

            Bug ID: 29865
           Summary: The GDB dies during unwind the stack - question
           Product: gdb
           Version: HEAD
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: gdb
          Assignee: unassigned at sourceware dot org
          Reporter: filip.bascarevic at siemens dot com
  Target Milestone: ---

Hello community,
I was debugging something and my GDB application just died when I wanted to do
"backtrace". After debugging the source code, I figure out the application died
at the assert in the file gdb/dwarf2/loc.c:1147 (in the function
dwarf_expr_reg_to_entry_parameter()). The reason why the assert is triggered is
because I setup the backtrace limit to 30 and during unwinding the stack the
frame type was "INLINE_FRAME" so the get_priv_frame() function returned NULL
(see line gdb/frame.c:2527) and the assert is triggered. 
Is it really necessary to have this assert? Why we need to consider if the
current frame is "INLINE_FRAME" on this place? 

Problematic code is:
    while (get_frame_type (frame) == INLINE_FRAME)
    {
      frame = get_prev_frame (frame);
      gdb_assert (frame != NULL);
    }

Thanks a lot for the support,
Filip Bascarevic

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[Bug gdb/29865] The GDB dies during unwind the stack - question

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=29865

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tromey at sourceware dot org

--- Comment #1 from Tom Tromey <tromey at sourceware dot org> ---
Offhand I'm not sure what the deal is here.
Maybe "set backtrace limit" has to take this situation
into account and allow some leeway, or maybe it
should only work on "physical" (non-inline/tailcall)
frames -- dunno.  (And, assuming that's what you did...)

However - what version of gdb are you using?
This assert doesn't seem to appear in git master.

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[Bug gdb/29865] The GDB dies during unwind the stack - question

[filip.bascarevic at siemens dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=29865

--- Comment #2 from Filip Bascarevic <filip.bascarevic at siemens dot com> ---
When I noticed the issue, I used gdb-10.2, but during report of the bug, I put
information from master in the gdb mirror from the GitHub. On this link you can
find problematic lines:
https://github.com/bminor/binutils-gdb/blob/b0f110a5ea0914aff686bab0f511d749433104d8/gdb/dwarf2/loc.c#L1144-L1148

Thanks for the support.
Also, if I can help somehow, just let me know.

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[Bug gdb/29865] The GDB dies during unwind the stack - question

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=29865

--- Comment #3 from Tom Tromey <tromey at sourceware dot org> ---
> Also, if I can help somehow, just let me know.

Well... if you're interested in hacking on gdb, maybe
the way to approach this is to change how the backtrace
limit works.  One idea is to have it only count "real"
frames and ignore inline frames and tailcall frames.

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[Bug gdb/29865] The GDB dies during unwind the stack - question

[ssbssa at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=29865

Hannes Domani <ssbssa at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ssbssa at sourceware dot org

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[Bug gdb/29865] The GDB dies during unwind the stack - question

[ssbssa at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=29865

Hannes Domani <ssbssa at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at sourceware dot org   |ssbssa at sourceware dot org

--- Comment #4 from Hannes Domani <ssbssa at sourceware dot org> ---
https://sourceware.org/pipermail/gdb-patches/2024-January/205693.html

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[Bug gdb/29865] The GDB dies during unwind the stack - question

[ssbssa at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=29865

Hannes Domani <ssbssa at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2024-01-06
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW

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[Bug gdb/29865] The GDB dies during unwind the stack - question

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=29865

--- Comment #5 from Sourceware Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Hannes Domani <ssbssa@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=633680620bb85ed6f80b22371ef49610faec8d03

commit 633680620bb85ed6f80b22371ef49610faec8d03
Author: Hannes Domani <ssbssa@yahoo.de>
Date:   Mon Jan 29 15:31:44 2024 +0100

    Fix backtrace limit stopping on inline frame

    If you have set up a backtrace limit, and the backtrace stops
    because of this in an inline frame with arguments, you get an
    assertion failure:
    ```
    (gdb) bt
    (gdb) set backtrace limit 2
    (gdb) bt
    C:/src/repos/binutils-gdb.git/gdb/frame.c:3346: internal-error: reinflate:
Assertion `m_cached_level >= -1' failed.
    ```

    And if this one is fixed, there is another one as well:
    ```
    (gdb) bt
    C:/src/repos/binutils-gdb.git/gdb/dwarf2/loc.c:1160: internal-error:
dwarf_expr_reg_to_entry_parameter: Assertion `frame != NULL' failed.
    ```

    The reason for both of them is this kind of loop:
    ```
      while (get_frame_type (frame) == INLINE_FRAME)
        frame = get_prev_frame (frame);
    ```
    Since get_prev_frame respects the backtrace limit, it will return
    NULL, and from there on you can't continue.
    This changes these loops to use get_prev_frame_always instead, so
    you always get a non-inline frame in the end.

    With this backtrace works:
    ```
    (gdb) bt
    (gdb)
    ```

    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29865
    Approved-By: Andrew Burgess <aburgess@redhat.com>

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[Bug gdb/29865] The GDB dies during unwind the stack - question

[ssbssa at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=29865

Hannes Domani <ssbssa at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED
   Target Milestone|---                         |15.1

--- Comment #6 from Hannes Domani <ssbssa at sourceware dot org> ---
Fixed.

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