diff options
| -rw-r--r-- | libstdc++-v3/ChangeLog | 4 | ||||
| -rw-r--r-- | libstdc++-v3/include/bits/cpp_type_traits.h | 11 |
2 files changed, 11 insertions, 4 deletions
diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog index ff8ae64..df3b040 100644 --- a/libstdc++-v3/ChangeLog +++ b/libstdc++-v3/ChangeLog @@ -1,3 +1,7 @@ +2020-03-04 Jonathan Wakely <jwakely@redhat.com> + + * include/bits/cpp_type_traits.h (__memcpyable): Fix comment. + 2020-03-04 Patrick Palka <ppalka@redhat.com> PR libstdc++/94017 diff --git a/libstdc++-v3/include/bits/cpp_type_traits.h b/libstdc++-v3/include/bits/cpp_type_traits.h index fac6e4b..979ad9c 100644 --- a/libstdc++-v3/include/bits/cpp_type_traits.h +++ b/libstdc++-v3/include/bits/cpp_type_traits.h @@ -429,10 +429,9 @@ __INT_N(__GLIBCXX_TYPE_INT_N_3) enum { __value = __is_trivially_copyable(_Tp) }; }; - // Cannot use memcpy/memmove/memcmp on volatile types, but before C++20 - // iterator_traits<volatile T*>::value_type is volatile T and so the - // partial specializations below match for volatile-qualified pointers - // e.g. __memcpyable<volatile int*, volatile int*, volatile int>. + // Cannot use memcpy/memmove/memcmp on volatile types even if they are + // trivially copyable, so ensure __memcpyable<volatile int*, volatile int*> + // and similar will be false. template<typename _Tp> struct __is_nonvolatile_trivially_copyable<volatile _Tp> { @@ -457,6 +456,10 @@ __INT_N(__GLIBCXX_TYPE_INT_N_3) { }; // Whether two iterator types can be used with memcmp. + // This trait only says it's well-formed to use memcmp, not that it + // gives the right answer for a given algorithm. So for example, std::equal + // needs to add additional checks that the types are integers or pointers, + // because other trivially copyable types can overload operator==. template<typename _Iter1, typename _Iter2> struct __memcmpable { |