[libc++][strings] P2591R5: Concatenation of strings and string views #88389
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@llvm/pr-subscribers-libcxx Author: Hristo Hristov (H-G-Hristov) ChangesImplemented: https://wg21.link/P2591R5 Full diff: https://github.com/llvm/llvm-project/pull/88389.diff 10 Files Affected:
diff --git a/libcxx/docs/FeatureTestMacroTable.rst b/libcxx/docs/FeatureTestMacroTable.rst
index 3197d2cd1b271c..0b8abe38e8bd77 100644
--- a/libcxx/docs/FeatureTestMacroTable.rst
+++ b/libcxx/docs/FeatureTestMacroTable.rst
@@ -456,6 +456,8 @@ Status
---------------------------------------------------------- -----------------
``__cpp_lib_sstream_from_string_view`` ``202306L``
---------------------------------------------------------- -----------------
+ ``__cpp_lib_string_view`` ``202403L``
+ ---------------------------------------------------------- -----------------
``__cpp_lib_submdspan`` *unimplemented*
---------------------------------------------------------- -----------------
``__cpp_lib_text_encoding`` *unimplemented*
diff --git a/libcxx/docs/ReleaseNotes/19.rst b/libcxx/docs/ReleaseNotes/19.rst
index 81c05b9112bd26..6fbac70593cc0b 100644
--- a/libcxx/docs/ReleaseNotes/19.rst
+++ b/libcxx/docs/ReleaseNotes/19.rst
@@ -45,6 +45,7 @@ Implemented Papers
- P2867R2 - Remove Deprecated ``strstream``\s From C++26
- P2872R3 - Remove ``wstring_convert`` From C++26
- P3142R0 - Printing Blank Lines with ``println`` (as DR against C++23)
+- P2591R5 - Concatenation of strings and string views
- P2302R4 - ``std::ranges::contains``
- P1659R3 - ``std::ranges::starts_with`` and ``std::ranges::ends_with``
diff --git a/libcxx/docs/Status/Cxx2cPapers.csv b/libcxx/docs/Status/Cxx2cPapers.csv
index fa11da62bc080e..8793d9385b79ae 100644
--- a/libcxx/docs/Status/Cxx2cPapers.csv
+++ b/libcxx/docs/Status/Cxx2cPapers.csv
@@ -55,7 +55,7 @@
"`P2845R8 <https://wg21.link/P2845R8>`__","LWG","Formatting of ``std::filesystem::path``","Tokyo March 2024","","","|format|"
"`P0493R5 <https://wg21.link/P0493R5>`__","LWG","Atomic minimum/maximum","Tokyo March 2024","","",""
"`P2542R8 <https://wg21.link/P2542R8>`__","LWG","``views::concat``","Tokyo March 2024","","","|ranges|"
-"`P2591R5 <https://wg21.link/P2591R5>`__","LWG","Concatenation of strings and string views","Tokyo March 2024","","",""
+"`P2591R5 <https://wg21.link/P2591R5>`__","LWG","Concatenation of strings and string views","Tokyo March 2024","|Complete|","19.0",""
"`P2248R8 <https://wg21.link/P2248R8>`__","LWG","Enabling list-initialization for algorithms","Tokyo March 2024","","",""
"`P2810R4 <https://wg21.link/P2810R4>`__","LWG","``is_debugger_present`` ``is_replaceable``","Tokyo March 2024","","",""
"`P1068R11 <https://wg21.link/P1068R11>`__","LWG","Vector API for random number generation","Tokyo March 2024","","",""
diff --git a/libcxx/include/string b/libcxx/include/string
index a456f8cb80ee35..7758a4ae42e046 100644
--- a/libcxx/include/string
+++ b/libcxx/include/string
@@ -407,6 +407,24 @@ template<class charT, class traits, class Allocator>
basic_string<charT, traits, Allocator>
operator+(const basic_string<charT, traits, Allocator>& lhs, charT rhs); // constexpr since C++20
+template<class charT, class traits, class Allocator>
+ constexpr basic_string<charT, traits, Allocator>
+ operator+(const basic_string<charT, traits, Allocator>& lhs,
+ type_identity_t<basic_string_view<charT, traits>> rhs); // Since C++26
+template<class charT, class traits, class Allocator>
+ constexpr basic_string<charT, traits, Allocator>
+ operator+(basic_string<charT, traits, Allocator>&& lhs,
+ type_identity_t<basic_string_view<charT, traits>> rhs); // Since C++26
+template<class charT, class traits, class Allocator>
+ constexpr basic_string<charT, traits, Allocator>
+ operator+(type_identity_t<basic_string_view<charT, traits>> lhs,
+ const basic_string<charT, traits, Allocator>& rhs); // Since C++26
+template<class charT, class traits, class Allocator>
+ constexpr basic_string<charT, traits, Allocator>
+ operator+(type_identity_t<basic_string_view<charT, traits>> lhs,
+ basic_string<charT, traits, Allocator>&& rhs); // Since C++26
+
+
template<class charT, class traits, class Allocator>
bool operator==(const basic_string<charT, traits, Allocator>& lhs,
const basic_string<charT, traits, Allocator>& rhs) noexcept; // constexpr since C++20
@@ -1074,8 +1092,8 @@ public:
__enable_if_t<__can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value &&
!__is_same_uncvref<_Tp, basic_string>::value,
int> = 0>
- _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS _LIBCPP_CONSTEXPR_SINCE_CXX20 explicit basic_string(
- const _Tp& __t, const allocator_type& __a)
+ _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
+ _LIBCPP_CONSTEXPR_SINCE_CXX20 explicit basic_string(const _Tp& __t, const allocator_type& __a)
: __r_(__default_init_tag(), __a) {
__self_view __sv = __t;
__init(__sv.data(), __sv.size());
@@ -1307,8 +1325,8 @@ public:
int> = 0>
_LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS _LIBCPP_CONSTEXPR_SINCE_CXX20
- basic_string&
- append(const _Tp& __t, size_type __pos, size_type __n = npos);
+ basic_string&
+ append(const _Tp& __t, size_type __pos, size_type __n = npos);
_LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string& append(const value_type* __s, size_type __n);
_LIBCPP_CONSTEXPR_SINCE_CXX20 basic_string& append(const value_type* __s);
@@ -1997,15 +2015,15 @@ private:
_LIBCPP_CONSTEXPR_SINCE_CXX20
#if _LIBCPP_ABI_VERSION >= 2 // We want to use the function in the dylib in ABIv1
- _LIBCPP_HIDE_FROM_ABI
+ _LIBCPP_HIDE_FROM_ABI
#endif
- _LIBCPP_DEPRECATED_("use __grow_by_without_replace") void __grow_by(
- size_type __old_cap,
- size_type __delta_cap,
- size_type __old_sz,
- size_type __n_copy,
- size_type __n_del,
- size_type __n_add = 0);
+ _LIBCPP_DEPRECATED_("use __grow_by_without_replace") void __grow_by(
+ size_type __old_cap,
+ size_type __delta_cap,
+ size_type __old_sz,
+ size_type __n_copy,
+ size_type __n_del,
+ size_type __n_add = 0);
_LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI void __grow_by_without_replace(
size_type __old_cap,
size_type __delta_cap,
@@ -2171,8 +2189,8 @@ template <class _CharT,
class _Traits,
class _Allocator = allocator<_CharT>,
class = enable_if_t<__is_allocator<_Allocator>::value> >
-explicit basic_string(basic_string_view<_CharT, _Traits>, const _Allocator& = _Allocator())
- -> basic_string<_CharT, _Traits, _Allocator>;
+explicit basic_string(basic_string_view<_CharT, _Traits>,
+ const _Allocator& = _Allocator()) -> basic_string<_CharT, _Traits, _Allocator>;
template <class _CharT,
class _Traits,
@@ -2407,15 +2425,15 @@ _LIBCPP_CONSTEXPR_SINCE_CXX20 void basic_string<_CharT, _Traits, _Allocator>::__
template <class _CharT, class _Traits, class _Allocator>
void _LIBCPP_CONSTEXPR_SINCE_CXX20
#if _LIBCPP_ABI_VERSION >= 2 // We want to use the function in the dylib in ABIv1
- _LIBCPP_HIDE_FROM_ABI
+_LIBCPP_HIDE_FROM_ABI
#endif
- _LIBCPP_DEPRECATED_("use __grow_by_without_replace") basic_string<_CharT, _Traits, _Allocator>::__grow_by(
- size_type __old_cap,
- size_type __delta_cap,
- size_type __old_sz,
- size_type __n_copy,
- size_type __n_del,
- size_type __n_add) {
+_LIBCPP_DEPRECATED_("use __grow_by_without_replace") basic_string<_CharT, _Traits, _Allocator>::__grow_by(
+ size_type __old_cap,
+ size_type __delta_cap,
+ size_type __old_sz,
+ size_type __n_copy,
+ size_type __n_del,
+ size_type __n_add) {
size_type __ms = max_size();
if (__delta_cap > __ms - __old_cap)
__throw_length_error();
@@ -4005,6 +4023,48 @@ operator+(basic_string<_CharT, _Traits, _Allocator>&& __lhs, _CharT __rhs) {
#endif // _LIBCPP_CXX03_LANG
+#if _LIBCPP_STD_VER >= 26
+
+template <class _CharT, class _Traits, class _Allocator>
+_LIBCPP_HIDE_FROM_ABI constexpr basic_string<_CharT, _Traits, _Allocator>
+operator+(const basic_string<_CharT, _Traits, _Allocator>& __lhs,
+ type_identity_t<basic_string_view<_CharT, _Traits>> __rhs) {
+ using _String = basic_string<_CharT, _Traits, _Allocator>;
+
+ _String __r = __lhs;
+ __r.append(__rhs);
+ return __r;
+}
+
+template <class _CharT, class _Traits, class _Allocator>
+_LIBCPP_HIDE_FROM_ABI constexpr basic_string<_CharT, _Traits, _Allocator>
+operator+(basic_string<_CharT, _Traits, _Allocator>&& __lhs,
+ type_identity_t<basic_string_view<_CharT, _Traits>> __rhs) {
+ __lhs.append(__rhs);
+ return std::move(__lhs);
+}
+
+template <class _CharT, class _Traits, class _Allocator>
+_LIBCPP_HIDE_FROM_ABI constexpr basic_string<_CharT, _Traits, _Allocator>
+operator+(type_identity_t<basic_string_view<_CharT, _Traits>> __lhs,
+ const basic_string<_CharT, _Traits, _Allocator>& __rhs) {
+ using _String = basic_string<_CharT, _Traits, _Allocator>;
+
+ _String __r = __rhs;
+ __r.insert(0, __lhs);
+ return __r;
+}
+
+template <class _CharT, class _Traits, class _Allocator>
+_LIBCPP_HIDE_FROM_ABI constexpr basic_string<_CharT, _Traits, _Allocator>
+operator+(type_identity_t<basic_string_view<_CharT, _Traits>> __lhs,
+ basic_string<_CharT, _Traits, _Allocator>&& __rhs) {
+ __rhs.insert(0, __lhs);
+ return std::move(__rhs);
+}
+
+#endif // _LIBCPP_STD_VER >= 26
+
// swap
template <class _CharT, class _Traits, class _Allocator>
diff --git a/libcxx/include/version b/libcxx/include/version
index 0ed77345baa71d..d7e98fdb47208d 100644
--- a/libcxx/include/version
+++ b/libcxx/include/version
@@ -222,7 +222,8 @@ __cpp_lib_stdatomic_h 202011L <stdatomic.h>
__cpp_lib_string_contains 202011L <string> <string_view>
__cpp_lib_string_resize_and_overwrite 202110L <string>
__cpp_lib_string_udls 201304L <string>
-__cpp_lib_string_view 201803L <string> <string_view>
+__cpp_lib_string_view 202403L <string> <string_view>
+ 201803L // C++20
201606L // C++17
__cpp_lib_submdspan 202306L <mdspan>
__cpp_lib_syncbuf 201803L <syncstream>
@@ -530,6 +531,8 @@ __cpp_lib_within_lifetime 202306L <type_traits>
# define __cpp_lib_span_at 202311L
# define __cpp_lib_span_initializer_list 202311L
# define __cpp_lib_sstream_from_string_view 202306L
+# undef __cpp_lib_string_view
+# define __cpp_lib_string_view 202403L
// # define __cpp_lib_submdspan 202306L
// # define __cpp_lib_text_encoding 202306L
# undef __cpp_lib_to_chars
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/string.version.compile.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/string.version.compile.pass.cpp
index 8d944a194faf42..4fb733716b99e2 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/string.version.compile.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/string.version.compile.pass.cpp
@@ -29,6 +29,7 @@
__cpp_lib_string_udls 201304L [C++14]
__cpp_lib_string_view 201606L [C++17]
201803L [C++20]
+ 202403L [C++26]
__cpp_lib_to_string 202306L [C++23]
*/
@@ -492,8 +493,8 @@
# ifndef __cpp_lib_string_view
# error "__cpp_lib_string_view should be defined in c++26"
# endif
-# if __cpp_lib_string_view != 201803L
-# error "__cpp_lib_string_view should have the value 201803L in c++26"
+# if __cpp_lib_string_view != 202403L
+# error "__cpp_lib_string_view should have the value 202403L in c++26"
# endif
# if !defined(_LIBCPP_VERSION)
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/string_view.version.compile.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/string_view.version.compile.pass.cpp
index a86ab2adff6a93..f3c70cf9779737 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/string_view.version.compile.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/string_view.version.compile.pass.cpp
@@ -23,6 +23,7 @@
__cpp_lib_string_contains 202011L [C++23]
__cpp_lib_string_view 201606L [C++17]
201803L [C++20]
+ 202403L [C++26]
*/
#include <string_view>
@@ -252,8 +253,8 @@
# ifndef __cpp_lib_string_view
# error "__cpp_lib_string_view should be defined in c++26"
# endif
-# if __cpp_lib_string_view != 201803L
-# error "__cpp_lib_string_view should have the value 201803L in c++26"
+# if __cpp_lib_string_view != 202403L
+# error "__cpp_lib_string_view should have the value 202403L in c++26"
# endif
#endif // TEST_STD_VER > 23
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp
index 3ec548f56cea1d..35bbfd916ac80a 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp
@@ -206,6 +206,7 @@
__cpp_lib_string_udls 201304L [C++14]
__cpp_lib_string_view 201606L [C++17]
201803L [C++20]
+ 202403L [C++26]
__cpp_lib_submdspan 202306L [C++26]
__cpp_lib_syncbuf 201803L [C++20]
__cpp_lib_text_encoding 202306L [C++26]
@@ -7686,8 +7687,8 @@
# ifndef __cpp_lib_string_view
# error "__cpp_lib_string_view should be defined in c++26"
# endif
-# if __cpp_lib_string_view != 201803L
-# error "__cpp_lib_string_view should have the value 201803L in c++26"
+# if __cpp_lib_string_view != 202403L
+# error "__cpp_lib_string_view should have the value 202403L in c++26"
# endif
# if !defined(_LIBCPP_VERSION)
diff --git a/libcxx/test/std/strings/basic.string/string.nonmembers/string_op+/string.string_view.pass.cpp b/libcxx/test/std/strings/basic.string/string.nonmembers/string_op+/string.string_view.pass.cpp
new file mode 100644
index 00000000000000..efa57442997e7f
--- /dev/null
+++ b/libcxx/test/std/strings/basic.string/string.nonmembers/string_op+/string.string_view.pass.cpp
@@ -0,0 +1,76 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20, c++23
+
+// <string>
+
+// [string.op.plus]
+//
+// template<class charT, class traits, class Allocator>
+// constexpr basic_string<charT, traits, Allocator>
+// operator+(const basic_string<charT, traits, Allocator>& lhs,
+// type_identity_t<basic_string_view<charT, traits>> rhs); // Since C++26
+// template<class charT, class traits, class Allocator>
+// constexpr basic_string<charT, traits, Allocator>
+// operator+(basic_string<charT, traits, Allocator>&& lhs,
+// type_identity_t<basic_string_view<charT, traits>> rhs); // Since C++26
+// template<class charT, class traits, class Allocator>
+// constexpr basic_string<charT, traits, Allocator>
+// operator+(type_identity_t<basic_string_view<charT, traits>> lhs,
+// const basic_string<charT, traits, Allocator>& rhs); // Since C++26
+// template<class charT, class traits, class Allocator>
+// constexpr basic_string<charT, traits, Allocator>
+// operator+(type_identity_t<basic_string_view<charT, traits>> lhs,
+// basic_string<charT, traits, Allocator>&& rhs); // Since C++26
+
+#include <cassert>
+#include <string>
+#include <utility>
+
+#include "asan_testing.h"
+#include "constexpr_char_traits.h"
+#include "make_string.h"
+#include "min_allocator.h"
+#include "test_macros.h"
+
+#define CS(S) MAKE_CSTRING(CharT, S)
+#define ST(S, a) std::basic_string<CharT, TraitsT, AllocT>(MAKE_CSTRING(CharT, S), MKSTR_LEN(CharT, S), a)
+#define SV(S) std::basic_string_view<CharT, TraitsT>(MAKE_CSTRING(CharT, S), MKSTR_LEN(CharT, S))
+
+template <typename CharT, typename TraitsT, typename AllocT>
+constexpr void test() {
+ AllocT allocator;
+ std::basic_string<CharT, TraitsT, AllocT> st{ST("Hello", allocator)};
+ std::basic_string_view<CharT, TraitsT> sv{SV("World")};
+
+ assert(st + sv == ST("HelloWorld", allocator));
+ assert(st + sv != ST("Hello World", allocator));
+}
+
+constexpr bool test() {
+ test<char, std::char_traits<char>, min_allocator<char>>();
+ test<char, constexpr_char_traits<char>, min_allocator<char>>();
+ test<char, std::char_traits<char>, safe_allocator<char>>();
+ test<char, constexpr_char_traits<char>, safe_allocator<char>>();
+#ifndef TEST_HAS_NO_WIDE_CHARACTERS
+ test<wchar_t, std::char_traits<wchar_t>, min_allocator<wchar_t>>();
+ test<wchar_t, constexpr_char_traits<wchar_t>, min_allocator<wchar_t>>();
+ test<wchar_t, std::char_traits<wchar_t>, safe_allocator<wchar_t>>();
+ test<wchar_t, constexpr_char_traits<wchar_t>, safe_allocator<wchar_t>>();
+#endif
+
+ return true;
+}
+
+int main(int, char**) {
+ test();
+ static_assert(test());
+
+ return 0;
+}
diff --git a/libcxx/utils/generate_feature_test_macro_components.py b/libcxx/utils/generate_feature_test_macro_components.py
index f2b8d55c0e11b0..1afdb6475b1877 100755
--- a/libcxx/utils/generate_feature_test_macro_components.py
+++ b/libcxx/utils/generate_feature_test_macro_components.py
@@ -1202,7 +1202,7 @@ def add_version_header(tc):
"values": {
"c++17": 201606,
"c++20": 201803,
- # "c++26": 202403, # P2591R5: Concatenation of strings and string views
+ "c++26": 202403, # P2591R5: Concatenation of strings and string views
},
"headers": ["string", "string_view"],
},
|
|
✅ With the latest revision this PR passed the Python code formatter. |
| operator+(basic_string<_CharT, _Traits, _Allocator>&& __lhs, | ||
| type_identity_t<basic_string_view<_CharT, _Traits>> __rhs) { | ||
| __lhs.append(__rhs); | ||
| return std::move(__lhs); |
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Not sure whether it would be better to drop std::move() here as __lhs is move-eligible here (ditto below).
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Thank you for the review. I reverted my interpretations to the original wording in the paper, so I'll keep this as is for now as I understand it this is our practice and also the older implementations uses the same style.
Zingam
changed the title
mordante
reviewed
Apr 13, 2024
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Thanks for working on this. In general it looks correct, but I wonder whether you considered the performance of the wording in the paper.
The paper explicitly states it does not consider this at all for the wording, see https://isocpp.org/files/papers/P2591R5.html#minimizingallocations. There is a link to https://github.com/llvm/llvm-project/blob/llvmorg-14.0.0/libcxx/include/string#L4218.
The paper also mentions an implementation by @hawkinsw (main...hawkinsw:llvm-project:P2591_string_view_concatenation) which at first glance did performance optimizations.
@hawkinsw did you benchmark your implementation?
(Note I read about the performance part in the paper after I already left some performance comments.)
libcxx/include/string
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| basic_string<_CharT, _Traits, _Allocator> __r = __lhs; | ||
| __r.append(__rhs); | ||
| return __r; |
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This is correct, however I wonder whether this is the optimal solution. Did you consider/benchmark different approaches like
basic_string<_CharT, _Traits, _Allocator> __r;
__r.reserve(__lhs.size() + __rhs.size());
__r.append(__lhs);
__r.append(__rhs);
or using resize_and_overwrite?
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I think select_on_container_copy_construction is needed to obtain the allocator of the result.
libcxx/include/string
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| basic_string<_CharT, _Traits, _Allocator> __r = __rhs; | ||
| __r.insert(0, __lhs); | ||
| return __r; |
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This also feels odd, here we copy rhs and directly afterwards move it. Did you consider alternative approaches avoiding doing extra work?
libcxx/test/std/strings/basic.string/string.nonmembers/string_op+/string.string_view.pass.cpp
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libcxx/test/std/strings/basic.string/string.nonmembers/string_op+/string.string_view.pass.cpp
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libcxx/test/std/strings/basic.string/string.nonmembers/string_op+/string.string_view.pass.cpp
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I did not, only because we were just doing it for "fun" at that point. Now that there is wider interest, I would be more than happy to do those benchmarks. I will respond as soon as I can!
|
|
@mordante @frederick-vs-ja Thank you for the feedback.
(this feels like a bug) which is even odder I am not able to reproduce the same behavior on compiler explorer |
Can you create a new branch in your repository with these issues and post the branch name here? Then I want to take a look at both issues. There is a work-around for the step limit; but based on how simple the tests are I wonder whether it's not infinite recursion. |
This is so cool. Thank you @H-G-Hristov! I am more than happy to help with benchmarking. I will be able to start work on it tonight -- sorry for the delay! Will
|
@mordante Thank you for helping! I use the pre-compiled LLVM-19 packages on Ubuntu. I have created two branches one for each issue: More details: This branch should demonstrate the This branch should demonstrate: constexpr evaluation hit maximum step limit; possible infinite loop? |
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This issue looks similar to #74221. I have an untested patch for that, but then other things came in between. I'll work on finishing that patch. |
mordante
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This was discovered by @StephanTLavavej who provided the solution they use in MSVC STL. This solution is based on that example. The same issue affects the constexpr_char_traits which was discovered in llvm#88389. This uses the same fix. Fixes: llvm#74221
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This was discovered by @StephanTLavavej who provided the solution they use in MSVC STL. This solution is based on that example. The same issue affects the constexpr_char_traits which was discovered in llvm#88389. This uses the same fix. Fixes: llvm#74221
mordante
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May 9, 2024
The issue in nasty_char_traits was discovered by @StephanTLavavej who provided the solution they use in MSVC STL. This solution is based on that example. The same issue affects the constexpr_char_traits which was discovered in #88389. This uses the same fix. Fixes: #74221
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✅ With the latest revision this PR passed the C/C++ code formatter. |
…iews' of https://github.com/H-G-Hristov/llvm-project into hgh/libcxx/P2591R5-Concatenation-of-string-and-string-views
H-G-Hristov
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May 10, 2024
libcxx/test/std/strings/basic.string/string.nonmembers/string_op+/string.string_view.pass.cpp
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H-G-Hristov
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May 10, 2024
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| // template<class charT, class traits, class Allocator> | ||
| // constexpr basic_string<charT, traits, Allocator> | ||
| // operator+(const basic_string<charT, traits, Allocator>& lhs, | ||
| // type_identity_t<basic_string_view<charT, traits>> rhs); // Since C++26 | ||
| // template<class charT, class traits, class Allocator> | ||
| // constexpr basic_string<charT, traits, Allocator> | ||
| // operator+(basic_string<charT, traits, Allocator>&& lhs, | ||
| // type_identity_t<basic_string_view<charT, traits>> rhs); // Since C++26 | ||
| // template<class charT, class traits, class Allocator> | ||
| // constexpr basic_string<charT, traits, Allocator> | ||
| // operator+(type_identity_t<basic_string_view<charT, traits>> lhs, | ||
| // const basic_string<charT, traits, Allocator>& rhs); // Since C++26 | ||
| // template<class charT, class traits, class Allocator> | ||
| // constexpr basic_string<charT, traits, Allocator> | ||
| // operator+(type_identity_t<basic_string_view<charT, traits>> lhs, | ||
| // basic_string<charT, traits, Allocator>&& rhs); // Since C++26 |
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Splitting the test for each overload will result in too much boilerplate. Should I do it?
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Quite often we do it separately. I see the other operator+ overloads of string also test more than one overload. So let's keep it.
Zingam
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May 20, 2024
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| // Create a `basic_string` to workaround clang bug: | ||
| // https://github.com/llvm/llvm-project/issues/92382 | ||
| // Comparison between pointers to a string literal and some other object results in constant evaluation failure. | ||
| std::basic_string<CharT, TraitsT, AllocT> st_{x, allocator}; | ||
| std::basic_string_view<CharT, TraitsT> sv{st_}; |
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For the record this is a workaround for: #92382
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@Zingam The LLVM-19 branching is in two weeks. It would be great if you have time to get this review done before that time. Is there a way for me to help you getting this done? |
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Sorry that I haven't been able to help as much on this as I would have liked. I will echo what @mordante said, "Is there anything that I can do to help?" |
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@mordante @hawkinsw Thank you for asking to help! I've been rather busy and unable to do much libc++ related work. It would be great to complete this PR in time for 19.0.
@mordante Is there anything else besides the benchmarks that you'd like to be addressed? |
dangelog
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Jul 12, 2024
| assert(result == expected); | ||
| assert(result.get_allocator() == allocator); | ||
| LIBCPP_ASSERT(is_string_asan_correct(sv + std::move(st))); | ||
| } |
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Would it also make sense to test string + convertible_to_string_view ?
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Sure it would! Thank you for suggesting!
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Implemented: https://wg21.link/P2591R5