[libc++] Add missed constexpr to erase(_if) in <string>
#129666
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@llvm/pr-subscribers-libcxx Author: A. Jiang (frederick-vs-ja) Changes
This patch implements the missed changes that were not tracked in a specific paper. Full diff: https://github.com/llvm/llvm-project/pull/129666.diff 4 Files Affected:
diff --git a/libcxx/docs/ReleaseNotes/21.rst b/libcxx/docs/ReleaseNotes/21.rst
index e7cfa625a132c..663514ce36681 100644
--- a/libcxx/docs/ReleaseNotes/21.rst
+++ b/libcxx/docs/ReleaseNotes/21.rst
@@ -52,6 +52,8 @@ Improvements and New Features
- Updated formatting library to Unicode 16.0.0.
+- ``std::erase`` and ``std::erase_if`` overloads for ``std::basic_string`` are made ``constexpr`` in C++20 and later.
+
Deprecations and Removals
-------------------------
diff --git a/libcxx/include/string b/libcxx/include/string
index 419e3eee6746e..8cbd859e70e73 100644
--- a/libcxx/include/string
+++ b/libcxx/include/string
@@ -516,10 +516,10 @@ basic_istream<charT, traits>&
getline(basic_istream<charT, traits>& is, basic_string<charT, traits, Allocator>& str);
template<class charT, class traits, class Allocator, class U>
-typename basic_string<charT, traits, Allocator>::size_type
+constexpr typename basic_string<charT, traits, Allocator>::size_type
erase(basic_string<charT, traits, Allocator>& c, const U& value); // C++20
template<class charT, class traits, class Allocator, class Predicate>
-typename basic_string<charT, traits, Allocator>::size_type
+constexpr typename basic_string<charT, traits, Allocator>::size_type
erase_if(basic_string<charT, traits, Allocator>& c, Predicate pred); // C++20
typedef basic_string<char> string;
@@ -4022,7 +4022,7 @@ getline(basic_istream<_CharT, _Traits>&& __is, basic_string<_CharT, _Traits, _Al
# if _LIBCPP_STD_VER >= 20
template <class _CharT, class _Traits, class _Allocator, class _Up>
-inline _LIBCPP_HIDE_FROM_ABI typename basic_string<_CharT, _Traits, _Allocator>::size_type
+_LIBCPP_HIDE_FROM_ABI inline constexpr typename basic_string<_CharT, _Traits, _Allocator>::size_type
erase(basic_string<_CharT, _Traits, _Allocator>& __str, const _Up& __v) {
auto __old_size = __str.size();
__str.erase(std::remove(__str.begin(), __str.end(), __v), __str.end());
@@ -4030,7 +4030,7 @@ erase(basic_string<_CharT, _Traits, _Allocator>& __str, const _Up& __v) {
}
template <class _CharT, class _Traits, class _Allocator, class _Predicate>
-inline _LIBCPP_HIDE_FROM_ABI typename basic_string<_CharT, _Traits, _Allocator>::size_type
+_LIBCPP_HIDE_FROM_ABI inline constexpr typename basic_string<_CharT, _Traits, _Allocator>::size_type
erase_if(basic_string<_CharT, _Traits, _Allocator>& __str, _Predicate __pred) {
auto __old_size = __str.size();
__str.erase(std::remove_if(__str.begin(), __str.end(), __pred), __str.end());
diff --git a/libcxx/test/std/strings/strings.erasure/erase.pass.cpp b/libcxx/test/std/strings/strings.erasure/erase.pass.cpp
index 35139dd6ad407..a5a542b40c52a 100644
--- a/libcxx/test/std/strings/strings.erasure/erase.pass.cpp
+++ b/libcxx/test/std/strings/strings.erasure/erase.pass.cpp
@@ -11,7 +11,7 @@
// <string>
// template <class charT, class traits, class Allocator, class U>
-// typename basic_string<charT, traits, Allocator>::size_type
+// constexpr typename basic_string<charT, traits, Allocator>::size_type
// erase(basic_string<charT, traits, Allocator>& c, const U& value);
#include <string>
@@ -22,7 +22,7 @@
#include "min_allocator.h"
template <class S, class U>
-void test0(S s, U val, S expected, std::size_t expected_erased_count) {
+constexpr void test0(S s, U val, S expected, std::size_t expected_erased_count) {
ASSERT_SAME_TYPE(typename S::size_type, decltype(std::erase(s, val)));
assert(expected_erased_count == std::erase(s, val));
LIBCPP_ASSERT(s.__invariants());
@@ -30,7 +30,7 @@ void test0(S s, U val, S expected, std::size_t expected_erased_count) {
}
template <class S>
-void test() {
+constexpr void test() {
test0(S(""), 'a', S(""), 0);
test0(S("a"), 'a', S(""), 1);
@@ -64,10 +64,17 @@ void test() {
test0(S("aba"), opt('c'), S("aba"), 0);
}
-int main(int, char**) {
+constexpr bool test() {
test<std::string>();
test<std::basic_string<char, std::char_traits<char>, min_allocator<char>>>();
test<std::basic_string<char, std::char_traits<char>, test_allocator<char>>>();
+ return true;
+}
+
+int main(int, char**) {
+ test();
+ static_assert(test());
+
return 0;
}
diff --git a/libcxx/test/std/strings/strings.erasure/erase_if.pass.cpp b/libcxx/test/std/strings/strings.erasure/erase_if.pass.cpp
index 5bedd394ee578..0f1c3fcf675eb 100644
--- a/libcxx/test/std/strings/strings.erasure/erase_if.pass.cpp
+++ b/libcxx/test/std/strings/strings.erasure/erase_if.pass.cpp
@@ -11,7 +11,7 @@
// <string>
// template <class charT, class traits, class Allocator, class Predicate>
-// typename basic_string<charT, traits, Allocator>::size_type
+// constexpr typename basic_string<charT, traits, Allocator>::size_type
// erase_if(basic_string<charT, traits, Allocator>& c, Predicate pred);
#include <string>
@@ -21,7 +21,7 @@
#include "min_allocator.h"
template <class S, class Pred>
-void test0(S s, Pred p, S expected, std::size_t expected_erased_count) {
+constexpr void test0(S s, Pred p, S expected, std::size_t expected_erased_count) {
ASSERT_SAME_TYPE(typename S::size_type, decltype(std::erase_if(s, p)));
assert(expected_erased_count == std::erase_if(s, p));
LIBCPP_ASSERT(s.__invariants());
@@ -29,7 +29,7 @@ void test0(S s, Pred p, S expected, std::size_t expected_erased_count) {
}
template <typename S>
-void test() {
+constexpr void test() {
auto isA = [](auto ch) { return ch == 'a'; };
auto isB = [](auto ch) { return ch == 'b'; };
auto isC = [](auto ch) { return ch == 'c'; };
@@ -66,10 +66,17 @@ void test() {
test0(S("aba"), True, S(""), 3);
}
-int main(int, char**) {
+constexpr bool test() {
test<std::string>();
test<std::basic_string<char, std::char_traits<char>, min_allocator<char>>>();
test<std::basic_string<char, std::char_traits<char>, test_allocator<char>>>();
+ return true;
+}
+
+int main(int, char**) {
+ test();
+ static_assert(test());
+
return 0;
}
|
`std::erase(_if)` for `basic_string` were made `constexpr` in C++20 by cplusplus/draft@2c1ab97 as follow-up changes of P0980R1. This patch implements the missed changes that were not tracked in a specific paper.
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philnik777
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Mar 4, 2025
philnik777
approved these changes
Mar 4, 2025
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/186/builds/7039 Here is the relevant piece of the build log for the reference |
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std::erase(_if)forbasic_stringwere madeconstexprin C++20 by cplusplus/draft@2c1ab97 as follow-up changes of P0980R1.This patch implements the missed changes that were not tracked in a specific paper.