Agreed, I'll revise the patch to do so. On Thu, Sep 23, 2021 at 12:07 PM Jakub Jelinek <ja...@redhat.com> wrote:
> On Thu, Sep 23, 2021 at 11:08:37AM -0700, Thomas Rodgers wrote: > > From: Thomas Rodgers <rodg...@twrodgers.com> > > > > This change implements P0528 which requires that padding bits not > > participate in atomic compare exchange operations. All arguments to the > > Thanks for working on this. > > > generic template are 'sanitized' by the __builtin_clear_padding intrinsic > > before they are used in atomic compare_exchange. This alrequires that any > > stores also sanitize the incoming value. > > Not a review, just random nit. > Shouldn't the __builtin_clear_padding calls be guarded with > #if __has_builtin(__builtin_clear_padding) > or #ifdef _GLIBCXX_HAVE_BUILTIN_CLEAR_PADDING defined based on that? > I think clang doesn't support it (yet?), and it doesn't support the MSVC > __builtin_zero_non_value_bits (with very similar, but slightly different, > behavior). > > > Signed-off-by: Thomas Rodgers <trodg...@redhat.com> > > > > libstdc++=v3/ChangeLog: > > > > * include/std/atomic (atomic<T>::atomic(_Tp) clear padding for > > __cplusplus > 201703L. > > (atomic<T>::store()) Clear padding. > > (atomic<T>::exchange()) Likewise. > > (atomic<T>::compare_exchange_weak()) Likewise. > > (atomic<T>::compare_exchange_strong()) Likewise. > > * testsuite/29_atomics/atomic/compare_exchange_padding.cc: New > > test. > > Jakub > >
