[Bug middle-end/101791] New: missing warning on a mismatch between scalar and array forms of new and delete

[Bug middle-end/101791] New: missing warning on a mismatch between scalar and array forms of new and delete

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101791

            Bug ID: 101791
           Summary: missing warning on a mismatch between scalar and array
                    forms of new and delete
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: msebor at gcc dot gnu.org
  Target Milestone: ---

The -Wmismatched-new-delete warning introduced in GCC 11 is meant to diagnose
calls to operator delete with pointers obtained from a mismatched form or
overload of operator new.  A poster child for such a mismatch is the scalar
form of a delete expression with an argument obtained from array new.  GCC 11
diagnoses such mismatches when they involve member operators new and delete (as
in g() below) but it fails to do the same for the default non-member operators
(as in h()).

$ cat t.C && gcc -S -Wall t.Ctypedef __SIZE_TYPE__ size_t;

struct A
{
  void* operator new (size_t);
  void operator delete (void*);

  void* operator new[] (size_t);
  void operator delete[] (void*);
};

void f (void*);

void g ()
{
  A *p = new A[7];
  f (p);
  delete p;        // -Wmismatched-new-delete (good)
}

void h ()
{
  int *p = new int[7];
  f (p);
  delete p;        // missing warning
}
t.C: In function ‘void g()’:
t.C:18:10: warning: ‘static void A::operator delete(void*)’ called on pointer
returned from a mismatched allocation function [-Wmismatched-new-delete]
   18 |   delete p;        // -Wmismatched-new-delete (good)
      |          ^
t.C:16:17: note: returned from ‘static void* A::operator new [](size_t)’
   16 |   A *p = new A[7];
      |                 ^

[Bug middle-end/101791] missing warning on a mismatch between scalar and array forms of new and delete

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101791

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |12.0
             Blocks|                            |100406
           Assignee|unassigned at gcc dot gnu.org      |msebor at gcc dot gnu.org
             Status|UNCONFIRMED                 |ASSIGNED
            Version|12.0                        |11.2.1
   Last reconfirmed|                            |2021-08-05
           Keywords|                            |diagnostic
     Ever confirmed|0                           |1


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100406
[Bug 100406] bogus/missing -Wmismatched-new-delete

[Bug middle-end/101791] missing warning on a mismatch between scalar and array forms of new and delete

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101791

--- Comment #1 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:96194a07bdbc57dd9733892a791d87dbe25f0802

commit r12-2908-g96194a07bdbc57dd9733892a791d87dbe25f0802
Author: Martin Sebor <msebor@redhat.com>
Date:   Sat Aug 14 13:25:41 2021 -0600

    Diagnose mismatches between array and scalar new and delete [PR101791].

    Resolves:
    PR middle-end/101791 - missing warning on a mismatch between scalar and
array forms of new and delete

    gcc/ChangeLog:

            PR middle-end/101791
            * gimple-ssa-warn-access.cc (new_delete_mismatch_p): Use new
argument
            to valid_new_delete_pair_p.
            * tree.c (valid_new_delete_pair_p): Add argument.
            * tree.h (valid_new_delete_pair_p): Same.

    gcc/testsuite/ChangeLog:

            PR middle-end/101791
            * g++.dg/warn/Wmismatched-new-delete-6.C: New test.
            * g++.dg/warn/Wmismatched-new-delete-7.C: New test.

[Bug middle-end/101791] missing warning on a mismatch between scalar and array forms of new and delete

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101791

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

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

--- Comment #2 from Martin Sebor <msebor at gcc dot gnu.org> ---
Fixed in r12-2908.