[Bug libstdc++/105375] New: std::packaged_task has no deduction guide.

[Bug libstdc++/105375] New: std::packaged_task has no deduction guide.

[raldone01 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105375

            Bug ID: 105375
           Summary: std::packaged_task has no deduction guide.
           Product: gcc
           Version: 11.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: raldone01 at gmail dot com
  Target Milestone: ---

According to cppreference
https://en.cppreference.com/w/cpp/thread/packaged_task/deduction_guides
std::packaged_task should have a deduction guide.
The example listed on their page does not compile.

gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-pc-linux-gnu/11.2.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /build/gcc/src/gcc/configure
--enable-languages=c,c++,ada,fortran,go,lto,objc,obj-c++,d --enable-bootstrap
--prefix=/usr --libdir=/usr/lib --libexecdir=/usr/lib --mandir=/usr/share/man
--infodir=/usr/share/info --with-bugurl=https://bugs.archlinux.org/
--with-linker-hash-style=gnu --with-system-zlib --enable-__cxa_atexit
--enable-cet=auto --enable-checking=release --enable-clocale=gnu
--enable-default-pie --enable-default-ssp --enable-gnu-indirect-function
--enable-gnu-unique-object --enable-linker-build-id --enable-lto
--enable-multilib --enable-plugin --enable-shared --enable-threads=posix
--disable-libssp --disable-libstdcxx-pch --disable-werror
--with-build-config=bootstrap-lto --enable-link-serialization=1
gdc_include_dir=/usr/include/dlang/gdc
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 11.2.0 (GCC)
System type: Ubuntu WSL

Command line: c++ -Wall -Wextra -g -std=gnu++20 -o lin.obj -c main.cpp

Expected behavior: The snipped from cppreference compiles.
Actual behavior:   The deduction guide for packaged_task is missing?

int func(double) { return 0; }
int main() {
    std::packaged_task f{func}; // deduces packaged_task<int(double)>
    int i = 5;
    std::packaged_task g = [&](double) { return i; }; // deduces
packaged_task<int(double)>
}

As std::function has deduction guides shouldn't std::packaged_task have some
too?

[Bug libstdc++/105375] std::packaged_task has no deduction guide.

[raldone01 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105375

--- Comment #1 from raldone01 <raldone01 at gmail dot com> ---
Created attachment 52866
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52866&action=edit
main.cpp

[Bug libstdc++/105375] std::packaged_task has no deduction guide.

[raldone01 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105375

--- Comment #2 from raldone01 <raldone01 at gmail dot com> ---
Created attachment 52867
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52867&action=edit
All the request files.

[Bug libstdc++/105375] std::packaged_task has no deduction guide.

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105375

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2022-04-25

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
cppreference says it's defined since C++17 but that's wrong, it was a
post-C++20 LWG issue: https://cplusplus.github.io/LWG/issue3117

We don't implement it yet.

[Bug libstdc++/105375] std::packaged_task has no deduction guide.

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105375

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Ah it's noted as a DR at
https://en.cppreference.com/w/cpp/thread/packaged_task#Defect_reports

[Bug libstdc++/105375] std::packaged_task has no deduction guide.

[raldone01 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105375

--- Comment #5 from raldone01 <raldone01 at gmail dot com> ---
Thank you for your reply.
What does that mean?
Are defect reports updates for older standards?
Is it meant to be available at some point in c++17?

[Bug libstdc++/105375] std::packaged_task has no deduction guide.

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105375

--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to raldone01 from comment #5)
> Thank you for your reply.
> What does that mean?

As it says at the link in comment 4, "The following behavior-changing defect
reports were applied retroactively to previously published C++ standards."

> Are defect reports updates for older standards?

Yes.

> Is it meant to be available at some point in c++17?

Yes.

[Bug libstdc++/105375] std::packaged_task has no deduction guide.

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105375

--- Comment #7 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jonathan Wakely <redi@gcc.gnu.org>:

https://gcc.gnu.org/g:a5cee0480c10bafa8ed65d49e5cedca23d98d7b7

commit r12-8249-ga5cee0480c10bafa8ed65d49e5cedca23d98d7b7
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Mon Apr 25 14:22:41 2022 +0100

    libstdc++: Add deduction guides for std::packaged_task [PR105375]

    This change was LWG 3117.

    The test is copied from 20_util/function/cons/deduction.cc

    libstdc++-v3/ChangeLog:

            PR libstdc++/105375
            * include/std/future (packaged_task): Add deduction guides.
            * testsuite/30_threads/packaged_task/cons/deduction.cc: New test.

[Bug libstdc++/105375] std::packaged_task has no deduction guide.

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105375

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |11.4

--- Comment #8 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Fixed for GCC 12, but worth backporting to GCC 11 too.

[Bug libstdc++/105375] std::packaged_task has no deduction guide.

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105375

--- Comment #9 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-11 branch has been updated by Jonathan Wakely
<redi@gcc.gnu.org>:

https://gcc.gnu.org/g:eb6f6f638a547f0330cc7940c5389039b59e4e76

commit r11-9936-geb6f6f638a547f0330cc7940c5389039b59e4e76
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Mon Apr 25 14:22:41 2022 +0100

    libstdc++: Add deduction guides for std::packaged_task [PR105375]

    This change was LWG 3117.

    The test is copied from 20_util/function/cons/deduction.cc

    libstdc++-v3/ChangeLog:

            PR libstdc++/105375
            * include/std/future (packaged_task): Add deduction guides.
            * testsuite/30_threads/packaged_task/cons/deduction.cc: New test.

    (cherry picked from commit a5cee0480c10bafa8ed65d49e5cedca23d98d7b7)

[Bug libstdc++/105375] std::packaged_task has no deduction guide.

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105375

Jonathan Wakely <redi at gcc dot gnu.org> changed:

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

--- Comment #10 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Fixed for 11.4 too.