[Bug rust/22574] New: support ptype/o in rust

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22574

Bug ID: 22574
Summary: support ptype/o in rust
Product: gdb
Version: HEAD
Status: NEW
Severity: normal
Priority: P2
Component: rust
Assignee: unassigned at sourceware dot org
Reporter: tromey at sourceware dot org
Target Milestone: ---

Bug 16224 is adding pahole-like functionality via "ptype/o".
The rust type printer should support this as well.

I have started a patch for this, so contact me if you plan
to pick this up.

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22574

Tom Tromey <tromey at sourceware dot org> changed:

What |Removed |Added
----------------------------------------------------------------------------
Depends on| |16224


Referenced Bugs:

https://sourceware.org/bugzilla/show_bug.cgi?id=16224
[Bug 16224] add "pahole" functionality to ptype

[sergiodj at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=22574
Bug 22574 depends on bug 16224, which changed state.

Bug 16224 Summary: add "pahole" functionality to ptype
https://sourceware.org/bugzilla/show_bug.cgi?id=16224

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

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22574

--- Comment #1 from Tom Tromey <tromey at sourceware dot org> ---
Given that the rust compiler reorders fields now, I wonder if
this is even worth doing. Holes seem not to be actionable in rust.
I'm considering just closing this bug.

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22574

--- Comment #2 from Tom Tromey <tromey at sourceware dot org> ---
Maybe it is still interesting sometimes to see a "layout view" of
a type in the debugger. That's the only case where I could think of
this being useful. The idea here is that since rustc reorders fields
we'd also need to sort of by offset before printing the type.

[palves at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=22574

Pedro Alves <palves at redhat dot com> changed:

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

--- Comment #3 from Pedro Alves <palves at redhat dot com> ---
You can use repr attributes control layout though:

https://doc.rust-lang.org/nomicon/other-reprs.html

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22574

Tom Tromey <tromey at sourceware dot org> changed:

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

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22574

--- Comment #4 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Tom Tromey <***@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=a33ccfc7afd9e32dd310f54d04719efeec8df342

commit a33ccfc7afd9e32dd310f54d04719efeec8df342
Author: Tom Tromey <***@tromey.com>
Date: Fri Jun 8 13:18:25 2018 -0600

Support ptype/o in Rust

This adds support for ptype/o to the Rust language code.

By default, the Rust compiler reorders fields to reduce padding. So,
the Rust language code sorts the fields by offset before printing.
This may yield somewhat odd-looking results, but it is faithful to
"what really happens", and might be useful when doing lower-level
debugging.

The reordering can be disabled using #[repr(c)]; ptype/o might be more
useful in this case.

gdb/ChangeLog
2018-06-26 Tom Tromey <***@tromey.com>

PR rust/22574:
* typeprint.c (whatis_exp): Allow ptype/o for Rust.
* rust-lang.c (rust_print_struct_def): Add podata parameter.
Update.
(rust_internal_print_type): Add podata parameter.
(rust_print_type): Update.

gdb/testsuite/ChangeLog
2018-06-26 Tom Tromey <***@tromey.com>

PR rust/22574:
* gdb.rust/simple.exp (test_one_slice): Add ptype/o tests.
* gdb.rust/simple.rs (struct SimpleLayout): New.

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22574

Tom Tromey <tromey at sourceware dot org> changed:

What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution|--- |FIXED
Target Milestone|--- |8.2

--- Comment #5 from Tom Tromey <tromey at sourceware dot org> ---
Fixed.