[Bug libstdc++/104395] New: alignof is a C++11 feature. src/c++98/bitmap_allocator.cc???

[Bug libstdc++/104395] New: alignof is a C++11 feature. src/c++98/bitmap_allocator.cc???

[unlvsur at live dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104395

            Bug ID: 104395
           Summary: alignof is a C++11 feature.
                    src/c++98/bitmap_allocator.cc???
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: unlvsur at live dot com
  Target Milestone: ---

https://github.com/gcc-mirror/gcc/blob/master/libstdc%2B%2B-v3/src/c%2B%2B98/bitmap_allocator.cc

https://github.com/gcc-mirror/gcc/blob/master/libstdc%2B%2B-v3/include/ext/bitmap_allocator.h

clang provides the option -faligned-allocation. It would define that macro even
in C++98 mode. Probably we need to detect whether __cplusplus >= 201103L?

/home/cqwrteur/myhome/gcc_build/native/wasm32-wasi/libstdc++-v3/include/ext/bitmap_allocator.h:1047:18:
error: unexpected type name 'value_type': expected expression
            if (alignof(value_type) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
                        ^

[Bug libstdc++/104395] alignof is a C++11 feature. src/c++98/bitmap_allocator.cc???

[unlvsur at live dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104395

--- Comment #1 from cqwrteur <unlvsur at live dot com> ---
/home/cqwrteur/myhome/gcc_build/native/wasm32-wasi/libstdc++-v3/include/ext/pool_allocator.h:274:16:
error: '_Tp' does not refer to a value
          if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
                      ^
Sounds like a weird issue in clang 15.

[Bug libstdc++/104395] alignof is a C++11 feature. src/c++98/bitmap_allocator.cc???

[unlvsur at live dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104395

cqwrteur <unlvsur at live dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |INVALID
             Status|UNCONFIRMED                 |RESOLVED

--- Comment #2 from cqwrteur <unlvsur at live dot com> ---
It seems to be other issues rather than this one. close.

[Bug libstdc++/104395] alignof is a C++11 feature. src/c++98/bitmap_allocator.cc???

[unlvsur at live dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104395

cqwrteur <unlvsur at live dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |UNCONFIRMED
         Resolution|INVALID                     |---

--- Comment #3 from cqwrteur <unlvsur at live dot com> ---
#include<ext/bitmap_allocator.h>
#include<ext/new_allocator.h>

int main()
{
        __gnu_cxx::new_allocator<int> n;
        n.allocate(3);
}

clang++ -o a a.cc -faligned-allocation -fsized-deallocation -s -flto
-fuse-ld=lld -std=c++98

/usr/local/bin/../lib/gcc/x86_64-pc-linux-gnu/12.0.1/../../../../include/c++/12.0.1/bits/new_allocator.h:55:21:
note: de
clared here
  template<typename _Tp>
                    ^
/usr/local/bin/../lib/gcc/x86_64-pc-linux-gnu/12.0.1/../../../../include/c++/12.0.1/bits/new_allocator.h:132:55:
error: '_Tp' does not refer to a value
            std::align_val_t __al = std::align_val_t(alignof(_Tp));


Sounds like a C++98 issue.

[Bug libstdc++/104395] alignof is a C++11 feature. src/c++98/bitmap_allocator.cc???

[unlvsur at live dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104395

--- Comment #4 from cqwrteur <unlvsur at live dot com> ---
also in all xxx_allocator.h including mt_allocator.h pool_allocator.h

[Bug libstdc++/104395] alignof is a C++11 feature. src/c++98/bitmap_allocator.cc???

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104395

--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
GCC's option is -faligned-new -fsized-deallocation -std=c++98

[Bug libstdc++/104395] ext/bitmap_allocator.h is not C++98 friendly when using with -faligned-new

[unlvsur at live dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104395

--- Comment #6 from cqwrteur <unlvsur at live dot com> ---
(In reply to Andrew Pinski from comment #5)
> GCC's option is -faligned-new -fsized-deallocation -std=c++98

yeah gcc does not work either.

[Bug libstdc++/104395] ext/bitmap_allocator.h is not C++98 friendly when using with -faligned-new

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104395

--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> ---
It doesn't seem very helpful for GCC and Clang to accept enum class align_val_t
in C++98 mode, but not accept alignof in system headers.

We could change all these uses to __alignof instead of alignof, which would
work with C++98. But the semantics of alignof and __alignof are slightly
different. Maybe the difference only matters for long long, and not for any
overaligned types, but I'm not sure.

I think the simple answer is that you should not use -faligned-new in C++98
mode.

[Bug libstdc++/104395] ext/bitmap_allocator.h is not C++98 friendly when using with -faligned-new

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104395

Jonathan Wakely <redi at gcc dot gnu.org> changed:

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

--- Comment #8 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Jonathan Wakely from comment #7)
> It doesn't seem very helpful for GCC and Clang to accept enum class
> align_val_t in C++98 mode, but not accept alignof in system headers.

It would only need to be accepted when -faligned-new / -faligned-allocation is
active, which is already requesting a non-standard extension to C++98.

[Bug libstdc++/104395] ext/bitmap_allocator.h is not C++98 friendly when using with -faligned-new

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104395

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                URL|                            |https://gcc.gnu.org/piperma
                   |                            |il/gcc-patches/2024-June/65
                   |                            |5842.html
   Last reconfirmed|                            |2024-06-27
           Keywords|                            |patch
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |redi at gcc dot gnu.org

--- Comment #9 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Patch posted: https://gcc.gnu.org/pipermail/gcc-patches/2024-June/655842.html

[Bug libstdc++/104395] ext/bitmap_allocator.h is not C++98 friendly when using with -faligned-new

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104395

--- Comment #10 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jonathan Wakely <redi@gcc.gnu.org>:

https://gcc.gnu.org/g:03d3aeb0e0fa7dec9bd702cabf57ef73cdc32704

commit r15-1714-g03d3aeb0e0fa7dec9bd702cabf57ef73cdc32704
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Wed Jun 26 14:09:07 2024 +0100

    libstdc++: Do not use C++11 alignof in C++98 mode [PR104395]

    When -faligned-new (or Clang's -faligned-allocation) is used our
    allocators try to support extended alignments, gated on the
    __cpp_aligned_new macro. However, because they use alignof(_Tp) which is
    not a keyword in C++98 mode, using -std=c++98 -faligned-new results in
    errors from <memory> and other headers.

    We could change them to use __alignof__ instead of alignof, but that
    would potentially alter the result of the conditions, because e.g.
    alignof(long long) != __alignof__(long long) on some targets. That's
    probably not an issue for any types with extended alignment, so maybe it
    would be a safe change.

    For now, it seems acceptable to just disable the extended alignment
    support in C++98 mode, so that -faligned-new enables std::align_val_t
    and the corresponding operator new overloads, but doesn't affect
    std::allocator, __gnu_cxx::__bitmap_allocator etc.

    libstdc++-v3/ChangeLog:

            PR libstdc++/104395
            * include/bits/new_allocator.h: Disable extended alignment
            support in C++98 mode.
            * include/bits/stl_tempbuf.h: Likewise.
            * include/ext/bitmap_allocator.h: Likewise.
            * include/ext/malloc_allocator.h: Likewise.
            * include/ext/mt_allocator.h: Likewise.
            * include/ext/pool_allocator.h: Likewise.
            * testsuite/ext/104395.cc: New test.