[Bug libstdc++/110602] New: std::format and friends are accessible without std::

[Bug libstdc++/110602] New: std::format and friends are accessible without std::

[tchaikov at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110602

            Bug ID: 110602
           Summary: std::format and friends are accessible without std::
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: tchaikov at gmail dot com
  Target Milestone: ---

following code should not compile as "format_to" should be placed in the "std"
namespace:

====8<====
#include <format>

std::string foo() {
    std::string ss;
    format_to(std::back_inserter(ss), "{}", 1);
    return ss;
}

int main() {
    return foo().size() != 1;
}
====>8====

but it compiles with gcc trunk (at the time of writing) and gcc 13.1. with
following command line options:

-std=c++23 -O2 -Wall -Wextra 

or 

-std=c++20 -O2 -Wall -Wextra 

i also tested clang + libstdc++ and clang + libc++. all of these combinations
compiles. see https://godbolt.org/z/GhrxPx7Gz for the reproducer.

i was trying to figure out by inspecting the preprocessed source file and
messing around with a sample code below to see if we somehow opened the std
namespace in format or some files included by it but failed:


std::string foo() {
    std::string ss;
    auto out = std::back_inserter(ss);
    // auto args = make_format_args(1, 2, 3);
    // basic_format_string<char, int, int> fmt_str{"{} {}"};
    auto std_args = std::make_format_args(1, 2, 3);
    auto std_wargs = std::make_wformat_args(1, 2, 3);
    // does not compile
    // auto args = std::make_format_args(1, 2, 3);
    // does not compile
    // auto wargs = std::make_wformat_args(1, 2, 3);

    vformat_to(out, "{} {} {}", std_args);
    auto s = vformat("{}", std_args);
    format_to(out, "{}", ss);
    return ss;
}

it turns out make_format_args and make_wformat_args are still in "std"
namespace, while format, format_to and vformat_to can be accessed with and
without qualified with 'std'

[Bug libstdc++/110602] std::format and friends are accessible without std::

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110602

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

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

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
This is how agrument depedent namelookup works.

[Bug libstdc++/110602] std::format and friends are accessible without std::

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110602

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
See https://en.cppreference.com/w/cpp/language/adl for a quick reference on the
subject.

[Bug libstdc++/110602] std::format and friends are accessible without std::

[tchaikov at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110602

--- Comment #3 from kefu chai <tchaikov at gmail dot com> ---
hi Andrew,

ahh, i missed that. thank you for pointing this out.

[Bug libstdc++/110602] std::format and friends are accessible without std::

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110602

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to kefu chai from comment #0)
> i also tested clang + libstdc++ and clang + libc++. all of these
> combinations compiles.

That's usually a sign the code is valid.