| Message ID | ae9efa7d-d3fa-4bc5-aefb-90add29a14da@kdab.com |
|---|---|
| State | New |
| Headers | show |
| Series | [1/6] libstdc++: port away from is_trivial in string classes | expand |
On 09/12/24 13:06 +0100, Giuseppe D'Angelo wrote: >Hello, > >This is a series of commits that will end up with the deprecation of >the is_trivial type trait in C++26 (P3247R2). > >Existing usages in libstdc+++ need to be ported away, either to the >direct replacement (is_trivially_copyable && >is_trivially_default_constructible) or, when possible, to more >specific checks (as "is_trivially_copyable" is a check which suffers >from the same flaws of "is_trivial"). > >I've split the work in multiple smaller commits for ease of review >(and amendment in case I get something wrong). Thanks, I'll amend the ChangeLog entry as noted below and then test+push this. I'll review the rest of the patch series too. When submitting patches please state how/where it was tested, just so the mailing list archives have a record that it was tested, and on which target. I typically just say "Tested x86_64-linux" as a shorthand for x86_64-pc-linux-gnu because I'm too lazy to type it all, and everybody knows what I mean. >Thanks, >-- >Giuseppe D'Angelo >From 1dcceca767df8e403bffd82a0d5e08d343bf33c5 Mon Sep 17 00:00:00 2001 >From: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com> >Date: Mon, 9 Dec 2024 01:43:27 +0100 >Subject: [PATCH 1/6] libstdc++: port away from is_trivial in string classes > >In preparation for the deprecation of is_trivial (P3247R2), stop using >it from std::string_view. Also, add the same detection to std::string >(described in [strings.general]/2). > >libstdc++-v3/ChangeLog: > > * include/bits/basic_string.h: add a static_assert on the Capital letter for "Add". > char-like type. N.B. this should be aligned to the '*' not the 'include'. > * include/std/string_view: port away from is_trivial. Capital letter for "Port". > >Signed-off-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com> >--- > libstdc++-v3/include/bits/basic_string.h | 3 +++ > libstdc++-v3/include/std/string_view | 4 +++- > 2 files changed, 6 insertions(+), 1 deletion(-) > >diff --git a/libstdc++-v3/include/bits/basic_string.h b/libstdc++-v3/include/bits/basic_string.h >index 17b973c8b45..8369c24d3ae 100644 >--- a/libstdc++-v3/include/bits/basic_string.h >+++ b/libstdc++-v3/include/bits/basic_string.h >@@ -88,6 +88,9 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11 > class basic_string > { > #if __cplusplus >= 202002L >+ static_assert(is_trivially_copyable_v<_CharT> >+ && is_trivially_default_constructible_v<_CharT> >+ && is_standard_layout_v<_CharT>); This only enables the assertion for C++20 and later, but I think that's fine. > static_assert(is_same_v<_CharT, typename _Traits::char_type>); > static_assert(is_same_v<_CharT, typename _Alloc::value_type>); > using _Char_alloc_type = _Alloc; >diff --git a/libstdc++-v3/include/std/string_view b/libstdc++-v3/include/std/string_view >index 96350f96b3c..493edec26dc 100644 >--- a/libstdc++-v3/include/std/string_view >+++ b/libstdc++-v3/include/std/string_view >@@ -108,7 +108,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION > class basic_string_view > { > static_assert(!is_array_v<_CharT>); >- static_assert(is_trivial_v<_CharT> && is_standard_layout_v<_CharT>); >+ static_assert(is_trivially_copyable_v<_CharT> >+ && is_trivially_default_constructible_v<_CharT> >+ && is_standard_layout_v<_CharT>); > static_assert(is_same_v<_CharT, typename _Traits::char_type>); > > public: >-- >2.34.1 >
From 1dcceca767df8e403bffd82a0d5e08d343bf33c5 Mon Sep 17 00:00:00 2001 From: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com> Date: Mon, 9 Dec 2024 01:43:27 +0100 Subject: [PATCH 1/6] libstdc++: port away from is_trivial in string classes In preparation for the deprecation of is_trivial (P3247R2), stop using it from std::string_view. Also, add the same detection to std::string (described in [strings.general]/2). libstdc++-v3/ChangeLog: * include/bits/basic_string.h: add a static_assert on the char-like type. * include/std/string_view: port away from is_trivial. Signed-off-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com> --- libstdc++-v3/include/bits/basic_string.h | 3 +++ libstdc++-v3/include/std/string_view | 4 +++- 2 files changed, 6 insertions(+), 1 deletion(-) diff --git a/libstdc++-v3/include/bits/basic_string.h b/libstdc++-v3/include/bits/basic_string.h index 17b973c8b45..8369c24d3ae 100644 --- a/libstdc++-v3/include/bits/basic_string.h +++ b/libstdc++-v3/include/bits/basic_string.h @@ -88,6 +88,9 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11 class basic_string { #if __cplusplus >= 202002L + static_assert(is_trivially_copyable_v<_CharT> + && is_trivially_default_constructible_v<_CharT> + && is_standard_layout_v<_CharT>); static_assert(is_same_v<_CharT, typename _Traits::char_type>); static_assert(is_same_v<_CharT, typename _Alloc::value_type>); using _Char_alloc_type = _Alloc; diff --git a/libstdc++-v3/include/std/string_view b/libstdc++-v3/include/std/string_view index 96350f96b3c..493edec26dc 100644 --- a/libstdc++-v3/include/std/string_view +++ b/libstdc++-v3/include/std/string_view @@ -108,7 +108,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION class basic_string_view { static_assert(!is_array_v<_CharT>); - static_assert(is_trivial_v<_CharT> && is_standard_layout_v<_CharT>); + static_assert(is_trivially_copyable_v<_CharT> + && is_trivially_default_constructible_v<_CharT> + && is_standard_layout_v<_CharT>); static_assert(is_same_v<_CharT, typename _Traits::char_type>); public: -- 2.34.1