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author | Jonathan Wakely <jwakely@redhat.com> | 2020-03-04 15:34:05 +0000 |
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committer | Jonathan Wakely <jwakely@redhat.com> | 2020-03-04 15:35:20 +0000 |
commit | 94f7d7ec6ebef49a50da777fd71db3d03ee03aa0 (patch) | |
tree | cb0a7e0ca537fb2e3c583f996f74e9a25b815571 /libstdc++-v3/include | |
parent | 0b0908c1f27d12a3cbbd3c9fd55aec1fe87586a6 (diff) | |
download | gcc-94f7d7ec6ebef49a50da777fd71db3d03ee03aa0.zip gcc-94f7d7ec6ebef49a50da777fd71db3d03ee03aa0.tar.gz gcc-94f7d7ec6ebef49a50da777fd71db3d03ee03aa0.tar.bz2 |
libstdc++: Fix comment on __memcpyable
The discussion of iterator_traits<volatile T*>::value_type and the
example with three tempalte arguments related to an earlier version of
the patch, not the one committed.
Also improve the comment on __memcmpable.
* include/bits/cpp_type_traits.h (__memcpyable): Fix comment.
Diffstat (limited to 'libstdc++-v3/include')
-rw-r--r-- | libstdc++-v3/include/bits/cpp_type_traits.h | 11 |
1 files changed, 7 insertions, 4 deletions
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 { |