[Bug libstdc++/99306] New: bootstrap failure on msdosdjgpp: error: alignment of 'm' is greater than maximum object file alignment 16

[Bug libstdc++/99306] New: bootstrap failure on msdosdjgpp: error: alignment of 'm' is greater than maximum object file alignment 16

[unlvsur at live dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99306

            Bug ID: 99306
           Summary: bootstrap failure on msdosdjgpp: error: alignment of
                    'm' is greater than maximum object file alignment 16
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: unlvsur at live dot com
  Target Milestone: ---

../../../../../gcc/libstdc++-v3/src/c++11/shared_ptr.cc:39:14: error: alignment
of 'm' is greater than maximum object file alignment 16
   39 |     static M m[mask + 1];
      |              ^
make[5]: *** [Makefile:648: shared_ptr.lo] Error 1
make[5]: *** Waiting for unfinished jobs....
../../../../../gcc/libstdc++-v3/src/c++11/cow-locale_init.cc: In member
function 'void std::locale::_Impl::_M_init_extra(void*, void*, const char*,
const char*)':
../../../../../gcc/libstdc++-v3/src/c++11/cow-locale_init.cc:140:50: warning:
unused parameter 'clocm' [-Wunused-parameter]
  140 |   locale::_Impl::_M_init_extra(void* cloc, void* clocm,
      |                                            ~~~~~~^~~~~
../../../../../gcc/libstdc++-v3/src/c++11/cow-locale_init.cc:141:61: warning:
unused parameter '__smon' [-Wunused-parameter]
  141 |                                const char* __s, const char* __smon)
      |                                                 ~~~~~~~~~~~~^~~~~~
make[4]: *** [Makefile:764: all-recursive] Error 1
make[3]: *** [Makefile:568: all-recursive] Error 1
make[2]: *** [Makefile:493: all] Error 2
make[1]: *** [Makefile:11838: all-target-libstdc++-v3] Error 2
make: *** [Makefile:970: all] Error 2

[Bug libstdc++/99306] cross compiler bootstrap failure on msdosdjgpp: error: alignment of 'm' is greater than maximum object file alignment 16

[unlvsur at live dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99306

--- Comment #1 from cqwrteur <unlvsur at live dot com> ---
Created attachment 50268
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=50268&action=edit
shared_ptr optional no alignment patch

[Bug libstdc++/99306] cross compiler bootstrap failure on msdosdjgpp: error: alignment of 'm' is greater than maximum object file alignment 16

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99306

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2021-03-01
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
  __gnu_cxx::__mutex&
  get_mutex(unsigned char i)
  {
    // increase alignment to put each lock on a separate cache line
    struct alignas(64) M : __gnu_cxx::__mutex { };
    static M m[mask + 1];
    return m[i];

there's __BIGGEST_ALIGNMENT__ one could use as bound but that will usually
be lower than the max ofile alignment and on most targets likely less
than 64.  That value (64) looks like it should be target dependent anyway
(configury?)

[Bug libstdc++/99306] cross compiler bootstrap failure on msdosdjgpp: error: alignment of 'm' is greater than maximum object file alignment 16

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99306

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
It's intended to be the cacheline size, so would use
std::hardware_destructive_interference_size, but that's not implemented yet for
the reasons given in PR 88466. And also because it's just a very verbose way to
say 64 :-P