[Bug c++/96021] New: missing -Wnonnull passing nullptr to a nonnull variadic lambda

[Bug c++/96021] New: missing -Wnonnull passing nullptr to a nonnull variadic lambda

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96021

            Bug ID: 96021
           Summary: missing -Wnonnull passing nullptr to a nonnull
                    variadic lambda
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: msebor at gcc dot gnu.org
  Target Milestone: ---

G++ issues -Wnonnull when passing nullptr to ordinary variadic functions but
not for the same problem involving variadic lambdas or unspecialized templates.
 I believe the problem is due to the -Wnonull warning checking for arguments of
pointer types and the nullptr constant not having such a type.

$ cat q.C && gcc -O2 -S -Wall q.C
__attribute__ ((nonnull)) void f (int, ...);
void ff ()
{
  f (1, nullptr);    // -Wnonnull (good)
}

template <class T> void g (T t)
{
  t (1, nullptr);    // missing -Wnonnull
}

void gg (void)
{
  g ([](int, auto...) __attribute__ ((nonnull)) { });
}

template <class T> __attribute__ ((nonnull)) void h (T);

void hh ()
{
  h (nullptr);       // missing -Wnonnull
}
q.C: In function ‘void ff()’:
q.C:4:16: warning: argument 2 null where non-null expected [-Wnonnull]
    4 |   f (1, nullptr);    // -Wnonnull (good)
      |                ^
q.C:1:32: note: in a call to function ‘void f(int, ...)’ declared ‘nonnull’
    1 | __attribute__ ((nonnull)) void f (int, ...);
      |                                ^

[Bug c++/96021] missing -Wnonnull passing nullptr to a nonnull variadic lambda

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96021

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Version|11.0                        |8.4.1
      Known to fail|                            |10.1.0, 11.0, 8.4.0, 9.3.0
           Keywords|                            |diagnostic
             Blocks|                            |95507

--- Comment #1 from Martin Sebor <msebor at gcc dot gnu.org> ---
This has never worked as expected.


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95507
[Bug 95507] [meta-bug] bogus/missing -Wnonnull

[Bug c++/96021] missing -Wnonnull passing nullptr to a nonnull variadic lambda

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96021

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
     Ever confirmed|0                           |1
           Assignee|unassigned at gcc dot gnu.org      |msebor at gcc dot gnu.org
   Last reconfirmed|                            |2020-07-01

--- Comment #2 from Martin Sebor <msebor at gcc dot gnu.org> ---
Fixed in my patch for pr95984.

[Bug c++/96021] missing -Wnonnull passing nullptr to a nonnull variadic lambda

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96021

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

https://gcc.gnu.org/g:67a493a0b9e7ce6caba4b8bedf1f3295e477ec00

commit r11-1860-g67a493a0b9e7ce6caba4b8bedf1f3295e477ec00
Author: Martin Sebor <msebor@redhat.com>
Date:   Mon Jul 6 15:23:37 2020 -0600

    Exclude calls to variadic lambda stubs from -Wnonnull checking (PR
c++/95984).

    Resolves:
    PR c++/95984 - Internal compiler error: Error reporting routines re-entered
in -Wnonnull on a variadic lamnda
    PR c++/96021 - missing -Wnonnull passing nullptr to a nonnull variadic
lambda

    gcc/c-family/ChangeLog:

            PR c++/95984
            * c-common.c (check_function_nonnull): Avoid checking syntesized
calls
            to stub lambda objects with null this pointer.
            (check_nonnull_arg): Handle C++ nullptr.

    gcc/cp/ChangeLog:

            PR c++/95984
            * call.c (build_over_call): Check calls only when tf_warning is
set.

    gcc/testsuite/ChangeLog:

            PR c++/95984
            * g++.dg/warn/Wnonnull6.C: New test.

[Bug c++/96021] missing -Wnonnull passing nullptr to a nonnull variadic lambda

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96021

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
   Target Milestone|---                         |11.0
             Status|ASSIGNED                    |RESOLVED

--- Comment #4 from Martin Sebor <msebor at gcc dot gnu.org> ---
Implemented for GCC 11 in r11-1860.