On Wed, 30 Jul 2025, Corinna Vinschen wrote: > On Jul 25 16:10, Jeremy Drake via Cygwin-patches wrote: > > A sized delete (with a std::size_t parameter) was added in C++14 (but > > doesn't combine with nothrow_t) > > > > An aligned new/delete (with a std::align_val_t parameter) was added in > > C++17, and combinations with the sized delete and nothrow_t variants. > > > > Signed-off-by: Jeremy Drake <cyg...@jdrake.com> > > --- > > I added #pragma GCC diagnostic ignored "-Wc++17-compat" preemptively to > > cxx.cc to match what was done with c++14-compat with the one sized delete > > that was already present (presumably because it broke things when GCC > > started to emit that instead of the non-sized delete). > > > > The default new implementation uses calloc, so I'm not sure if it's > > expected that the aligned new call memset to zero the returned memory. > > It'd be easy enough to add if necessary. > > > > GCC will need to be updated circa > > https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=gcc/config/i386/cygwin-w64.h;h=160a290a03d00f6408252f5d8751fea7cd44e1be;hb=HEAD#l27 > > but only after this change is stable because it will cause linker errors > > if the new __wrap symbols are not exported. > > > > Does there need to be a version bump somewhere to make sure a module > > linked against a new libcygwin.a doesn't run against an old cygwin1.dll, > > resulting in _cygwin_crt0_common.cc writing too much data to > > default_cygwin_cxx_malloc? > > > > winsup/cygwin/cxx.cc | 120 +++++++++++++++++++++- > > winsup/cygwin/cygwin.din | 12 +++ > > winsup/cygwin/lib/_cygwin_crt0_common.cc | 59 +++++++++++ > > winsup/cygwin/libstdcxx_wrapper.cc | 99 ++++++++++++++++++ > > winsup/cygwin/local_includes/cygwin-cxx.h | 14 +++ > > 5 files changed, 299 insertions(+), 5 deletions(-) > > LGTM. Please push (to main only, at least for now)
Done. I was figuring this was a 3.7-only change. I was thinking, in _cygwin_crt0_common.cc where the __cygwin_cxx_malloc struct is handled, perhaps it could "CONDITIONALLY_OVERRIDE" into the newu->cxx_malloc struct (from the dll) directly instead of merging into the local __cygwin_cxx_malloc struct and copying the entire struct over the dll struct. This might allow a binary built against a newer libcygwin.a to not crash (or corrupt memory) if run against an older dll, as long as the newer C++ new/delete operators were not defined. The sticking point would be libstdc++-6.dll once it is rebuilt with the additional --wrap arguments in GCC, because it would define all the operators and thus be incompatbile with older dll versions.
