[Bug c++/110164] New: Improve diagnostic for incomplete standard library types due to missing include

[Bug c++/110164] New: Improve diagnostic for incomplete standard library types due to missing include

[rs2740 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110164

            Bug ID: 110164
           Summary: Improve diagnostic for incomplete standard library
                    types due to missing include
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Keywords: diagnostic
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rs2740 at gmail dot com
  Target Milestone: ---

If I forget to include a header before using a sufficiently well-known standard
library type, GCC helpfully reminds me of the header:

$ echo 'std::array<int, 10> x;' | g++ -x c++ -

<stdin>:1:6: error: ‘array’ in namespace ‘std’ does not name a template type
<stdin>:1:1: note: ‘std::array’ is defined in header ‘<array>’; did you forget
to ‘#include <array>’?

But if I happen to have a different standard library header included that
happens to bring in a forward declaration of the type, the error message is
less helpful:

$ echo -e '#include <map>\nstd::array<int, 10> x;' | g++ -x c++ -

<stdin>:2:21: error: aggregate ‘std::array<int, 10> x’ has incomplete type and
cannot be defined

It would be nice if the latter case also has a hint about the potential missing
include.

[Bug c++/110164] Improve diagnostic for incomplete standard library types due to missing include

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110164

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement
   Last reconfirmed|                            |2023-06-07
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=39730

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed.

[Bug c++/110164] Improve diagnostic for incomplete standard library types due to missing include

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110164

David Malcolm <dmalcolm at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
                 CC|                            |dmalcolm at gcc dot gnu.org

--- Comment #2 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
Thanks for filing this.  I'm testing a patch for it.

[Bug c++/110164] Improve diagnostic for incomplete standard library types due to missing include

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110164

David Malcolm <dmalcolm at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                URL|                            |https://gcc.gnu.org/piperma
                   |                            |il/gcc-patches/2023-June/62
                   |                            |1779.html
           Keywords|                            |patch
             Status|ASSIGNED                    |WAITING
           Assignee|unassigned at gcc dot gnu.org      |dmalcolm at gcc dot gnu.org

--- Comment #3 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
Patch posted here awaiting review:
  https://gcc.gnu.org/pipermail/gcc-patches/2023-June/621779.html

[Bug c++/110164] Improve diagnostic for incomplete standard library types due to missing include

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110164

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |ASSIGNED

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Waiting status is for waiting from the reporter of the bug; in this case it is
waiting on approval of the patch rather than waiting on the reporter so
assigned is the correct status.

[Bug c++/110164] Improve diagnostic for incomplete standard library types due to missing include

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110164

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by David Malcolm <dmalcolm@gcc.gnu.org>:

https://gcc.gnu.org/g:13709b518aa9769ef427e48ce5c9583fbe098777

commit r14-2055-g13709b518aa9769ef427e48ce5c9583fbe098777
Author: David Malcolm <dmalcolm@redhat.com>
Date:   Fri Jun 23 17:56:14 2023 -0400

    c++: provide #include hint for missing includes [PR110164]

    PR c++/110164 notes that in cases where we have a forward decl
    of a std library type such as:

    std::array<int, 10> x;

    we emit this diagnostic:

    error: aggregate âstd::array<int, 10> xâ has incomplete type and cannot
be defined

    This patch adds this hint to the diagnostic:

    note: âstd::arrayâ is defined in header â<array>â; this is probably
fixable by adding â#include <array>â

    gcc/cp/ChangeLog:
            PR c++/110164
            * cp-name-hint.h (maybe_suggest_missing_header): New decl.
            * decl.cc: Define INCLUDE_MEMORY.  Add include of
            "cp/cp-name-hint.h".
            (start_decl_1): Call maybe_suggest_missing_header.
            * name-lookup.cc (maybe_suggest_missing_header): Remove "static".

    gcc/testsuite/ChangeLog:
            PR c++/110164
            * g++.dg/diagnostic/missing-header-pr110164.C: New test.

    Signed-off-by: David Malcolm <dmalcolm@redhat.com>

[Bug c++/110164] Improve diagnostic for incomplete standard library types due to missing include

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110164

David Malcolm <dmalcolm at gcc dot gnu.org> changed:

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

--- Comment #6 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
Should be fixed on trunk for gcc 14 by the above patch.