[Bug c++/98249] New: Improper ADL on the `arg` in `new (arg) T`

[Bug c++/98249] New: Improper ADL on the `arg` in `new (arg) T`

[arthur.j.odwyer at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98249

            Bug ID: 98249
           Summary: Improper ADL on the `arg` in `new (arg) T`
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: arthur.j.odwyer at gmail dot com
  Target Milestone: ---

// https://godbolt.org/z/xavfej

#include <new>
struct Incomplete;
template<class T> struct Holder { T t; };
Holder<Incomplete> *p;
void test() {
    ::new (p) int;
    new (p) int;
}

In an "ADL call," the compiler needs to compute the associated types of
`Holder<Incomplete>`, which means it needs to complete that type in order to
check for friend declarations.  In a "non-ADL call" (such as a qualified call),
the compiler does NOT need to complete `Holder<Incomplete>`.  Since completing
`Holder<Incomplete>` produces a hard error, we can detect the difference
between an ADL and a non-ADL call.

All other compilers use "non-ADL calls" for both `::new (p) int` and `new (p)
int`: they don't attempt to complete the incomplete type. GCC uses "ADL calls"
for both, which means it hard-errors on both lines.

I'm not sure what the Standard has to say about this, but GCC disagrees with
all of Clang/MSVC/ICC, so I think GCC ought to change.

(Detected while testing libc++ patch https://reviews.llvm.org/D92884)

[Bug c++/98249] Improper ADL on the `arg` in `new (arg) T`

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98249

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to fail|                            |4.5.3
           Keywords|                            |rejects-valid
      Known to work|                            |4.4.7

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Hmm, something changed between GCC 4.5 and 4.4 which caused this to be rejected
...

[Bug c++/98249] [9/10/11/12 Regression] Improper ADL on the `arg` in `new (arg) T`

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98249

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |9.5
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=34158
            Summary|Improper ADL on the `arg`   |[9/10/11/12 Regression]
                   |in `new (arg) T`            |Improper ADL on the `arg`
                   |                            |in `new (arg) T`

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I suspect the cause was the patch for PR 34158 (but I could be wrong).

[Bug c++/98249] [9/10/11/12 Regression] Improper ADL on the `arg` in `new (arg) T`

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98249

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2022-04-11
           Assignee|unassigned at gcc dot gnu.org      |jason at gcc dot gnu.org
                 CC|                            |jason at gcc dot gnu.org
     Ever confirmed|0                           |1

[Bug c++/98249] [9/10/11/12 Regression] Improper ADL on the `arg` in `new (arg) T`

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98249

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jason Merrill <jason@gcc.gnu.org>:

https://gcc.gnu.org/g:d087b59527a658a4de13febbb593edbf03339e93

commit r12-8093-gd087b59527a658a4de13febbb593edbf03339e93
Author: Jason Merrill <jason@redhat.com>
Date:   Mon Apr 11 13:06:05 2022 -0400

    c++: operator new lookup [PR98249]

    The standard says, as we quote in the comment just above, that if we don't
    find operator new in the allocated type, it should be looked up in the
    global scope.  This is specifically ::, not just any namespace, and we
    already give an error for an operator new declared in any other namespace.

            PR c++/98249

    gcc/cp/ChangeLog:

            * call.cc (build_operator_new_call): Just look in ::.

    gcc/testsuite/ChangeLog:

            * g++.dg/lookup/new3.C: New test.

[Bug c++/98249] [9/10/11 Regression] Improper ADL on the `arg` in `new (arg) T`

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98249

--- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-11 branch has been updated by Jason Merrill
<jason@gcc.gnu.org>:

https://gcc.gnu.org/g:7aa5f05583066f5b3146c999319288631c75597f

commit r11-9830-g7aa5f05583066f5b3146c999319288631c75597f
Author: Jason Merrill <jason@redhat.com>
Date:   Mon Apr 11 13:06:05 2022 -0400

    c++: operator new lookup [PR98249]

    The standard says, as we quote in the comment just above, that if we don't
    find operator new in the allocated type, it should be looked up in the
    global scope.  This is specifically ::, not just any namespace, and we
    already give an error for an operator new declared in any other namespace.

            PR c++/98249

    gcc/cp/ChangeLog:

            * call.c (build_operator_new_call): Just look in ::.

    gcc/testsuite/ChangeLog:

            * g++.dg/lookup/new3.C: New test.

[Bug c++/98249] [9/10 Regression] Improper ADL on the `arg` in `new (arg) T`

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98249

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Jason Merrill
<jason@gcc.gnu.org>:

https://gcc.gnu.org/g:6c69f7c449cc1c0d48e13b8680023a59f541260e

commit r10-10719-g6c69f7c449cc1c0d48e13b8680023a59f541260e
Author: Jason Merrill <jason@redhat.com>
Date:   Mon Apr 11 13:06:05 2022 -0400

    c++: operator new lookup [PR98249]

    The standard says, as we quote in the comment just above, that if we don't
    find operator new in the allocated type, it should be looked up in the
    global scope.  This is specifically ::, not just any namespace, and we
    already give an error for an operator new declared in any other namespace.

            PR c++/98249

    gcc/cp/ChangeLog:

            * call.c (build_operator_new_call): Just look in ::.

    gcc/testsuite/ChangeLog:

            * g++.dg/lookup/new3.C: New test.

[Bug c++/98249] [9 Regression] Improper ADL on the `arg` in `new (arg) T`

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98249

--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-9 branch has been updated by Jason Merrill
<jason@gcc.gnu.org>:

https://gcc.gnu.org/g:86d50501e487597d8b97f40d1c87dfcd694a9441

commit r9-10172-g86d50501e487597d8b97f40d1c87dfcd694a9441
Author: Jason Merrill <jason@redhat.com>
Date:   Mon Apr 11 13:06:05 2022 -0400

    c++: operator new lookup [PR98249]

    The standard says, as we quote in the comment just above, that if we don't
    find operator new in the allocated type, it should be looked up in the
    global scope.  This is specifically ::, not just any namespace, and we
    already give an error for an operator new declared in any other namespace.

            PR c++/98249

    gcc/cp/ChangeLog:

            * call.c (build_operator_new_call): Just look in ::.

    gcc/testsuite/ChangeLog:

            * g++.dg/lookup/new3.C: New test.

[Bug c++/98249] [9 Regression] Improper ADL on the `arg` in `new (arg) T`

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98249

Jason Merrill <jason at gcc dot gnu.org> changed:

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

--- Comment #7 from Jason Merrill <jason at gcc dot gnu.org> ---
Fixed for 9.5/10.4/11.4/12.