[Bug c++/102049] New: Extend attribute deprecated to allow optional 2nd argument

[Bug c++/102049] New: Extend attribute deprecated to allow optional 2nd argument

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102049

            Bug ID: 102049
           Summary: Extend attribute deprecated to allow optional 2nd
                    argument
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mpolacek at gcc dot gnu.org
  Target Milestone: ---

Clang implements something we don't have:

__attribute__((deprecated("message", "replacement")));

which we reject.  We probably could allow it for the [[gnu::deprecated]]
form too (but not [[deprecated]]).

I wonder if we want some tweak that if the replacement argument is an
empty string, we don't warn -- this should allow code bases to gradually move
away from deprecated functions only when there's an actual replacement.

[[gnu::deprecated("insecure", "")]] void f(); // no replacement yet, don't warn
[[gnu::deprecated("slow", "add2")]] void add(); // warn, use add2

Does this seem worthwhile?

[Bug c++/102049] Extend attribute deprecated to allow optional 2nd argument

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102049

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement
           Keywords|                            |diagnostic

[Bug c++/102049] Extend attribute deprecated to allow optional 2nd argument

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102049

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2021-08-25
                 CC|                            |msebor at gcc dot gnu.org

--- Comment #1 from Martin Sebor <msebor at gcc dot gnu.org> ---
Supporting the two-argument form for compatibility with Clang makes sense to
me.

I'm not sure I understand what letting the empty string as the second argument
suppress warnings would be useful for.  The only purpose of declaring something
deprecated that I know of is to trigger a warning when it's used, so unless I'm
missing something, that doesn't seem necessary or a good idea (if no warning is
wanted then remove the attribute).

[Bug c++/102049] Extend attribute deprecated to allow optional 2nd argument

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102049

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |mpolacek at gcc dot gnu.org

[Bug c++/102049] Extend attribute deprecated to allow optional 2nd argument

[egallager at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102049

Eric Gallager <egallager at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |egallager at gcc dot gnu.org

--- Comment #2 from Eric Gallager <egallager at gcc dot gnu.org> ---
It'd also be useful to have the compiler generate fixit hints to use the
replacement, too, when that's possible

[Bug c++/102049] Extend attribute deprecated to allow optional 2nd argument

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102049

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

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

--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Closing due to not enough interest.

My patch was:
https://gcc.gnu.org/pipermail/gcc-patches/2021-September/580179.html

[Bug c++/102049] Extend attribute deprecated to allow optional 2nd argument

[egallager at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102049

--- Comment #4 from Eric Gallager <egallager at gcc dot gnu.org> ---
(In reply to Marek Polacek from comment #3)
> Closing due to not enough interest.
> 
> My patch was:
> https://gcc.gnu.org/pipermail/gcc-patches/2021-September/580179.html

Wait, I was interested!