···1+diff --git a/include/my_char_traits.h b/include/my_char_traits.h
2+new file mode 100644
3+index 00000000..6336bc03
4+--- /dev/null
5++++ b/include/my_char_traits.h
6+@@ -0,0 +1,65 @@
7++/* Copyright (c) 2024, Oracle and/or its affiliates.
8++
9++ This program is free software; you can redistribute it and/or modify
10++ it under the terms of the GNU General Public License, version 2.0,
11++ as published by the Free Software Foundation.
12++
13++ This program is designed to work with certain software (including
14++ but not limited to OpenSSL) that is licensed under separate terms,
15++ as designated in a particular file or component or in included license
16++ documentation. The authors of MySQL hereby grant you an additional
17++ permission to link the program and your derivative works with the
18++ separately licensed software that they have either included with
19++ the program or referenced in the documentation.
20++
21++ This program is distributed in the hope that it will be useful,
22++ but WITHOUT ANY WARRANTY; without even the implied warranty of
23++ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
24++ GNU General Public License, version 2.0, for more details.
25++
26++ You should have received a copy of the GNU General Public License
27++ along with this program; if not, write to the Free Software
28++ Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
29++
30++#ifndef MY_CHAR_TRAITS_INCLUDED
31++#define MY_CHAR_TRAITS_INCLUDED
32++
33++#include <cstring>
34++
35++template <class CharT>
36++struct my_char_traits;
37++
38++/*
39++ This is a standards-compliant, drop-in replacement for
40++ std::char_traits<unsigned char>
41++ We need this because clang libc++ is removing support for it in clang 19.
42++ It is not a complete implementation. Rather we implement just enough to
43++ compile any usage of char_traits<uchar> we have in our codebase.
44++ */
45++template <>
46++struct my_char_traits<unsigned char> {
47++ using char_type = unsigned char;
48++ using int_type = unsigned int;
49++
50++ static void assign(char_type &c1, const char_type &c2) { c1 = c2; }
51++
52++ static char_type *assign(char_type *s, std::size_t n, char_type a) {
53++ return static_cast<char_type *>(memset(s, a, n));
54++ }
55++
56++ static int compare(const char_type *s1, const char_type *s2, std::size_t n) {
57++ return memcmp(s1, s2, n);
58++ }
59++
60++ static char_type *move(char_type *s1, const char_type *s2, std::size_t n) {
61++ if (n == 0) return s1;
62++ return static_cast<char_type *>(memmove(s1, s2, n));
63++ }
64++
65++ static char_type *copy(char_type *s1, const char_type *s2, std::size_t n) {
66++ if (n == 0) return s1;
67++ return static_cast<char_type *>(memcpy(s1, s2, n));
68++ }
69++};
70++
71++#endif // MY_CHAR_TRAITS_INCLUDED
72+diff --git a/sql/mdl_context_backup.h b/sql/mdl_context_backup.h
73+index 89e7e23d..cf9c307e 100644
74+--- a/sql/mdl_context_backup.h
75++++ b/sql/mdl_context_backup.h
76+@@ -28,6 +28,7 @@
77+ #include <map>
78+ #include <memory>
79+80++#include "my_char_traits.h"
81+ #include "sql/malloc_allocator.h"
82+ #include "sql/mdl.h"
83+84+@@ -47,7 +48,8 @@ class MDL_context_backup_manager {
85+ /**
86+ Key for uniquely identifying MDL_context in the MDL_context_backup map.
87+ */
88+- typedef std::basic_string<uchar> MDL_context_backup_key;
89++ using MDL_context_backup_key =
90++ std::basic_string<uchar, my_char_traits<uchar>>;
91+92+ class MDL_context_backup;
93+94+diff --git a/sql/stream_cipher.h b/sql/stream_cipher.h
95+index 606d4064..358fbb41 100644
96+--- a/sql/stream_cipher.h
97++++ b/sql/stream_cipher.h
98+@@ -28,6 +28,8 @@
99+ #include <memory>
100+ #include <string>
101+102++#include "my_char_traits.h"
103++
104+ /**
105+ @file stream_cipher.h
106+107+@@ -35,7 +37,8 @@
108+ binary log files.
109+ */
110+111+-typedef std::basic_string<unsigned char> Key_string;
112++using Key_string =
113++ std::basic_string<unsigned char, my_char_traits<unsigned char>>;
114+115+ /**
116+ @class Stream_cipher
117+diff --git a/unittest/gunit/binlogevents/transaction_compression-t.cc b/unittest/gunit/binlogevents/transaction_compression-t.cc
118+index ba13f979..01af0e3a 100644
119+--- a/unittest/gunit/binlogevents/transaction_compression-t.cc
120++++ b/unittest/gunit/binlogevents/transaction_compression-t.cc
121+@@ -23,6 +23,7 @@
122+ */
123+124+ #include <array>
125++#include <string>
126+127+ #include <gtest/gtest.h>
128+ #include "libbinlogevents/include/binary_log.h"
129+@@ -51,14 +52,13 @@ class TransactionPayloadCompressionTest : public ::testing::Test {
130+ using Managed_buffer_t = Decompressor_t::Managed_buffer_t;
131+ using Size_t = Decompressor_t::Size_t;
132+ using Char_t = Decompressor_t::Char_t;
133+- using String_t = std::basic_string<Char_t>;
134+ using Decompress_status_t =
135+ binary_log::transaction::compression::Decompress_status;
136+ using Compress_status_t =
137+ binary_log::transaction::compression::Compress_status;
138+139+- static String_t constant_data(Size_t size) {
140+- return String_t(size, (Char_t)'a');
141++ static std::string constant_data(Size_t size) {
142++ return std::string(size, (Char_t)'a');
143+ }
144+145+ protected:
146+@@ -69,7 +69,7 @@ class TransactionPayloadCompressionTest : public ::testing::Test {
147+ void TearDown() override {}
148+149+ static void compression_idempotency_test(Compressor_t &c, Decompressor_t &d,
150+- String_t data) {
151++ const std::string &data) {
152+ auto debug_string = concat(
153+ binary_log::transaction::compression::type_to_string(c.get_type_code()),
154+ " ", data.size());
155+@@ -104,8 +104,8 @@ class TransactionPayloadCompressionTest : public ::testing::Test {
156+157+ // Check decompressed data
158+ ASSERT_EQ(managed_buffer.read_part().size(), data.size()) << debug_string;
159+- ASSERT_EQ(data, String_t(managed_buffer.read_part().begin(),
160+- managed_buffer.read_part().end()))
161++ ASSERT_EQ(data, std::string(managed_buffer.read_part().begin(),
162++ managed_buffer.read_part().end()))
163+ << debug_string;
164+165+ // Check that we reached EOF
166+@@ -118,7 +118,7 @@ TEST_F(TransactionPayloadCompressionTest, CompressDecompressZstdTest) {
167+ for (auto size : buffer_sizes) {
168+ binary_log::transaction::compression::Zstd_dec d;
169+ binary_log::transaction::compression::Zstd_comp c;
170+- String_t data{TransactionPayloadCompressionTest::constant_data(size)};
171++ std::string data{TransactionPayloadCompressionTest::constant_data(size)};
172+ TransactionPayloadCompressionTest::compression_idempotency_test(c, d, data);
173+ c.set_compression_level(22);
174+ TransactionPayloadCompressionTest::compression_idempotency_test(c, d, data);
175+@@ -129,7 +129,7 @@ TEST_F(TransactionPayloadCompressionTest, CompressDecompressNoneTest) {
176+ for (auto size : buffer_sizes) {
177+ binary_log::transaction::compression::None_dec d;
178+ binary_log::transaction::compression::None_comp c;
179+- String_t data{TransactionPayloadCompressionTest::constant_data(size)};
180++ std::string data{TransactionPayloadCompressionTest::constant_data(size)};
181+ TransactionPayloadCompressionTest::compression_idempotency_test(c, d, data);
182+ }
183+ }