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From: "raldone01 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug libstdc++/105375] New: std::packaged_task has no deduction guide.
Date: Mon, 25 Apr 2022 12:49:03 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D105375

            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=3Dgcc
COLLECT_LTO_WRAPPER=3D/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=3Dc,c++,ada,fortran,go,lto,objc,obj-c++,d --enable-boots=
trap
--prefix=3D/usr --libdir=3D/usr/lib --libexecdir=3D/usr/lib --mandir=3D/usr=
/share/man
--infodir=3D/usr/share/info --with-bugurl=3Dhttps://bugs.archlinux.org/
--with-linker-hash-style=3Dgnu --with-system-zlib --enable-__cxa_atexit
--enable-cet=3Dauto --enable-checking=3Drelease --enable-clocale=3Dgnu
--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=3Dposix
--disable-libssp --disable-libstdcxx-pch --disable-werror
--with-build-config=3Dbootstrap-lto --enable-link-serialization=3D1
gdc_include_dir=3D/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=3Dgnu++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 =3D 5;
    std::packaged_task g =3D [&](double) { return i; }; // deduces
packaged_task<int(double)>
}

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