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[libc++] Add missed constexpr to erase(_if) in <string> #129666

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Merged
merged 3 commits into from
Mar 5, 2025
Merged

[libc++] Add missed constexpr to erase(_if) in <string> #129666

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073d679
[libc++] Add missed `constexpr` to `erase(_if)` in `<string>`
frederick-vs-ja Mar 4, 2025
f5856f8
Merge branch 'main' into constexpr-string-erase
frederick-vs-ja Mar 4, 2025
0577ad7
Revert changes in release notes per @philnik777's comments
frederick-vs-ja Mar 4, 2025
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2 changes: 2 additions & 0 deletions libcxx/docs/ReleaseNotes/21.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -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
-------------------------

Expand Down
8 changes: 4 additions & 4 deletions libcxx/include/string
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Expand Up @@ -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;
Expand Down Expand Up @@ -4022,15 +4022,15 @@ 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
inline _LIBCPP_HIDE_FROM_ABI 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());
return __old_size - __str.size();
}

template <class _CharT, class _Traits, class _Allocator, class _Predicate>
inline _LIBCPP_HIDE_FROM_ABI typename basic_string<_CharT, _Traits, _Allocator>::size_type
inline _LIBCPP_HIDE_FROM_ABI 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());
Expand Down
15 changes: 11 additions & 4 deletions libcxx/test/std/strings/strings.erasure/erase.pass.cpp
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Expand Up @@ -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>
Expand All @@ -22,15 +22,15 @@
#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());
assert(s == expected);
}

template <class S>
void test() {
constexpr void test() {
test0(S(""), 'a', S(""), 0);

test0(S("a"), 'a', S(""), 1);
Expand Down Expand Up @@ -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;
}
15 changes: 11 additions & 4 deletions libcxx/test/std/strings/strings.erasure/erase_if.pass.cpp
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Expand Up @@ -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>
Expand All @@ -21,15 +21,15 @@
#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());
assert(s == expected);
}

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'; };
Expand Down Expand Up @@ -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;
}