https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102772
--- Comment #41 from Jakub Jelinek <jakub at gcc dot gnu.org> --- (In reply to Jonathan Wakely from comment #39) > (In reply to r...@cebitec.uni-bielefeld.de from comment #37) > > AFAICS, alignof is C++ >= 11 only. I've used the attached patch to > > use __alignof__ instead, although I don't know if that's the best fix. > > Yes, alignof is C++11 only, but the reason it's OK to use there is that > __STDCPP_DEFAULT_NEW_ALIGNMENT__ is C++17 only, and alignof is guarded by: > > #if __cpp_aligned_new > if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__) > > Strictly speaking, this code is enabled when -faligned-new is active, which > is true for C++17 by default. > > It appears that Jakub's patch makes -faligned-new always active for Solaris > x86, which we don't want. Ah, indeed, I thought the threshold is separate from it being enabled, but it is not. So, we want to change it in the option override handling only if cxx_dialect >= cxx17, but that is something only defined in c-family, while the backend option overriding is in code linked with all FEs. Thus, we'd need to override it instead somewhere in i386-c.cc. But nothing in that file is called early enough, from what I can see, the sequence of initialization is: cxx_dialect set to the default (cxx17 now) possibly cxx_dialect changed if -std= used on command line SUBTARGET_OVERRIDE_OPTIONS invoked cxx_init_decl_processing 4645 if (aligned_new_threshold == -1) 4646 aligned_new_threshold = (cxx_dialect >= cxx17) ? 1 : 0; 4647 if (aligned_new_threshold == 1) 4648 aligned_new_threshold = malloc_alignment () / BITS_PER_UNIT; code invoked ix86_register_pragmas from i386-c.cc called ix86_target_macros from i386-c.cc called Also, the -Waligned-new= warning uses malloc_alignment () rather than aligned_new_threshold, so if we want to override something for 32-bit x86 solaris, mingw and vxworks, we probably need something to hook into malloc_alignment rather than to tweak aligned_new_threshold. I think we need a target macro for it though rather than target hook, because it needs to be invoked from the C++ FE and implemented in config/*-c.cc
