[Bug rust/31517] New: GDB 15 broke Rust upstream GDB tests

[Bug rust/31517] New: GDB 15 broke Rust upstream GDB tests

[liushuyu011 at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31517

            Bug ID: 31517
           Summary: GDB 15 broke Rust upstream GDB tests
           Product: gdb
           Version: HEAD
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: rust
          Assignee: unassigned at sourceware dot org
          Reporter: liushuyu011 at gmail dot com
  Target Milestone: ---

Created attachment 15423
  --> https://sourceware.org/bugzilla/attachment.cgi?id=15423&action=edit
Error logs

Hi there,

Recently, I tried building and running Rust 1.76 testsuites on my device, and I
encountered a slew of errors when the test runner started to run GDB-related
tests.

The errors were like this: (see the log file attached).

I remember those tests passing before, so I did some digging on GDB, and I
found this commit:
https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=b0dd661fa16a424f059b1e1d80e779508b1a9a12
that caused this kind of error.

I am unsure if this new behaviour is intentional. If it is, how should someone
print out the size of a Rust slice in this case?

I have also opened a bug report on the Rust upstream:
https://github.com/rust-lang/rust/issues/122751, in case GDB cannot do anything
to fix this situation (so that Rust upstream can fix their tests instead).

Thanks!

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[Bug rust/31517] GDB 15 broke Rust upstream GDB tests

[liushuyu011 at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31517

--- Comment #1 from liushuyu <liushuyu011 at gmail dot com> ---
If you don't want to run all the tests, you may just check this one:
https://raw.githubusercontent.com/rust-lang/rust/e3df96cfda905301fc8514e000f942222c1ab6ad/tests/debuginfo/vec-slices.rs

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[Bug rust/31517] GDB 15 broke Rust upstream GDB tests

[doko at debian dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31517

Matthias Klose <doko at debian dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |doko at debian dot org

--- Comment #2 from Matthias Klose <doko at debian dot org> ---
checked with trunk 20240312 and 20240320

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[Bug rust/31517] [15 Regression] GDB 15 broke Rust upstream GDB tests

[doko at debian dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31517

Matthias Klose <doko at debian dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|GDB 15 broke Rust upstream  |[15 Regression] GDB 15
                   |GDB tests                   |broke Rust upstream GDB
                   |                            |tests

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[Bug rust/31517] [15 Regression] GDB 15 broke Rust upstream GDB tests

[doko at debian dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31517

Matthias Klose <doko at debian dot org> changed:

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

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[Bug rust/31517] [15 Regression] GDB 15 broke Rust upstream GDB tests

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31517

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at sourceware dot org   |tromey at sourceware dot org
   Target Milestone|---                         |15.1

--- Comment #3 from Tom Tromey <tromey at sourceware dot org> ---
The gdb change was intentional.  See bug #30330.

There's also a follow-up patch that will land before gdb 15:
https://sourceware.org/pipermail/gdb-patches/2024-March/207190.html

This patch slightly changes the output in some cases.

In fact... let's use this bug to track that patch, to make sure
it really does land for 15.

> If it is, how should someone print out the size of a Rust slice in this case?

I built vec-slices.rs and ran it under a gdb with the patch
applied:

(gdb) info local
mut_slice = &mut [i64] [1, 2, 3, 4, 5]
padded_struct = &[vec_slices::AStruct] [
  vec_slices::AStruct {x: 10, y: 11, z: 12}, 
  vec_slices::AStruct {x: 13, y: 14, z: 15}]
padded_tuple = &[(i32, i16)] [(6, 7), (8, 9)]
slice_of_slice = &[i64] [3, 4]
multiple = &[i64] [2, 3, 4, 5]
singleton = &[i64] [1]
empty = &[i64] []

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[Bug rust/31517] [15 Regression] GDB 15 broke Rust upstream GDB tests

[liushuyu011 at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31517

--- Comment #4 from liushuyu <liushuyu011 at gmail dot com> ---
> I built vec-slices.rs and ran it under a gdb with the patch
> applied:

Thanks for the information!
Although I am curious about how to print the length of a slice like using
`print slice.length` before?

I have also built a GDB with the patch applied; the auto-completion in the
interactive mode still completes `.length` in this case:

(gdb) p multiple.
data_ptr  length    

Is this expected?

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[Bug rust/31517] [15 Regression] GDB 15 broke Rust upstream GDB tests

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31517

--- Comment #5 from Tom Tromey <tromey at sourceware dot org> ---
(In reply to liushuyu from comment #4)

> Although I am curious about how to print the length of a slice like using
> `print slice.length` before?

You can't, not directly anyway.
In Rust you use len() but the Rust compiler doesn't emit enough information
for gdb to do calls via traits.

> I have also built a GDB with the patch applied; the auto-completion in the
> interactive mode still completes `.length` in this case:
> 
> (gdb) p multiple.
> data_ptr  length    
> 
> Is this expected?

No, this should have a separate report.
The completer still sees the underlying C-like type.

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[Bug rust/31517] [15 Regression] Rust upstream GDB tests regressions with GDB 15

[brobecker at gnat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31517

Joel Brobecker <brobecker at gnat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[15 Regression] GDB 15      |[15 Regression] Rust
                   |broke Rust upstream GDB     |upstream GDB tests
                   |tests                       |regressions with GDB 15
                 CC|                            |brobecker at gnat dot com

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[Bug rust/31517] [15 Regression] Rust upstream GDB tests regressions with GDB 15

[brobecker at gnat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31517

--- Comment #6 from Joel Brobecker <brobecker at gnat dot com> ---
Hello,

From what I could understand, Tom is saying that there is no issue in GDB, and
so we should be able to close this PR?

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[Bug rust/31517] [15 Regression] Rust upstream GDB tests regressions with GDB 15

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31517

--- Comment #7 from Tom Tromey <tromey at sourceware dot org> ---
I want to land the patch mentioned in comment#3 first.

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[Bug rust/31517] [15 Regression] Rust upstream GDB tests regressions with GDB 15

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31517

--- Comment #8 from Sourceware Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Tom Tromey <tromey@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=251cedaeb57fe1e0fd28798f476fbee75373bbf4

commit 251cedaeb57fe1e0fd28798f476fbee75373bbf4
Author: Tom Tromey <tromey@adacore.com>
Date:   Thu Mar 7 12:57:07 2024 -0700

    Print type name when printing Rust slice

    The recent change to how unsized Rust values are printed included a
    small regression from past behavior.  Previously, a slice's type would
    be printed, like:

        (gdb) print slice
        $80 = &[i32] [3]

    The patch changed this to just

        (gdb) print slice
        $80 = [3]

    This patch restores the previous behavior.

    Reviewed-By: Simon Marchi <simon.marchi@efficios.com>
    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30330
    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31517

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[Bug rust/31517] [15 Regression] Rust upstream GDB tests regressions with GDB 15

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31517

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|UNCONFIRMED                 |RESOLVED

--- Comment #9 from Tom Tromey <tromey at sourceware dot org> ---
I am going to close this now.

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