[Bug c++/112377] New: Implement -Walloc-size in c++

[Bug c++/112377] New: Implement -Walloc-size in c++

[dcb314 at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112377

            Bug ID: 112377
           Summary: Implement -Walloc-size in c++
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dcb314 at hotmail dot com
  Target Milestone: ---

Following on from discussion in bug report 112347,
in file gcc/c-family/c.opt, is the new text

Walloc-size
C ObjC Var(warn_alloc_size) Warning LangEnabledBy(C ObjC, Wextra)
Warn when allocating insufficient storage for the target type of the assigned
pointer.

IMHO, it should say:

Walloc-size
C ObjC Var(warn_alloc_size) Warning LangEnabledBy(C ObjC C++, Wextra)
Warn when allocating insufficient storage for the target type of the assigned
pointer.

I think that should be enough to implement the new warning for C++.

[Bug c++/112377] Implement -Walloc-size in c++

[uecker at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112377

uecker at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2023-11-04
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1

--- Comment #1 from uecker at gcc dot gnu.org ---
Confirmed. 

But this change would not be enough. The warning is implemented in the C
front-end which which is separate from the C++ FE. Possibly, the code for the
warning could be shared, but I do not know.

[Bug c++/112377] Implement -Walloc-size in c++

[uecker at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112377

uecker at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement

[Bug c++/112377] Implement -Walloc-size in c++

[egallager at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112377

Eric Gallager <egallager at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |egallager at gcc dot gnu.org

--- Comment #2 from Eric Gallager <egallager at gcc dot gnu.org> ---
(In reply to David Binderman from comment #0)
> Following on from discussion in bug report 112347,
> in file gcc/c-family/c.opt, is the new text
> 
> Walloc-size
> C ObjC Var(warn_alloc_size) Warning LangEnabledBy(C ObjC, Wextra)
> Warn when allocating insufficient storage for the target type of the
> assigned pointer.
> 
> IMHO, it should say:
> 
> Walloc-size
> C ObjC Var(warn_alloc_size) Warning LangEnabledBy(C ObjC C++, Wextra)
> Warn when allocating insufficient storage for the target type of the
> assigned pointer.
> 
> I think that should be enough to implement the new warning for C++.

If adding it to C++, then IMO it ought to be enabled for ObjC++, too, since the
current implementation is for both C and ObjC.

[Bug c++/112377] Implement -Walloc-size in c++

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112377

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to David Binderman from comment #0)
> I think that should be enough to implement the new warning for C++.

Certainly not. Apart from the fact that there's a lot more needed than just
making the option accepted by the C++ front end, there's the question of what
it should actually do.

Would it only warn for malloc, calloc etc., or operator new as well?

And what about warning about alignment for overaligned types, both when using
operator new (with or without a std::align_val_t argument) and malloc. Should
that be a separate warning?