tests fail to build with clang-19 and libc++ due to unsupported `std::char_traits`

[paparodeo]

Description

when using clang-19 with libc++ the build fails to build the tests

In file included from /build/source/tests/src/unit-bson.cpp:9:
In file included from /build/source/tests/thirdparty/doctest/doctest_compatibility.h:6:
In file included from /build/source/tests/thirdparty/doctest/doctest.h:514:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ostream:177:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:24:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ios:561:20: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
  561 |   typedef typename traits_type::int_type int_type;
      |                    ^
...
fatal error: too many errors emitted, stopping now [-ferror-limit=]
20 errors generated.

https://releases.llvm.org/19.1.0/projects/libcxx/docs/ReleaseNotes.html

The base template for std::char_traits has been removed in LLVM 19. If you are using std::char_traits with types other than char, wchar_t, char8_t, char16_t, char32_t or a custom character type for which you specialized std::char_traits, your code will stop working. The Standard does not mandate that a base template is provided, and such a base template is bound to be incorrect for some types, which could currently cause unexpected behavior while going undetected.

Reproduction steps

nix-build -E 'with import <nixpkgs>{}; nlohmann_json.override { stdenv = llvmPackages_19.libcxxStdenv; }'

Expected vs. actual results

expect build to succeed like it does when using an earlier clang / libc++ combination.

Minimal code example

failing tests are:

• unit-bson.cpp
• unit-cbor.cpp
• unit-deserialization.cpp
• unit-msgpack.cpp
• unit-regression2.cpp

Error messages

Running phase: unpackPhase
@nix { "action": "setPhase", "phase": "unpackPhase" }
unpacking source archive /nix/store/balg02bsn0aazljy4yilygkm8piy26m6-source
source root is source
Running phase: patchPhase
@nix { "action": "setPhase", "phase": "patchPhase" }
Running phase: updateAutotoolsGnuConfigScriptsPhase
@nix { "action": "setPhase", "phase": "updateAutotoolsGnuConfigScriptsPhase" }
Running phase: configurePhase
@nix { "action": "setPhase", "phase": "configurePhase" }
fixing cmake files...
cmake flags: -DCMAKE_FIND_USE_SYSTEM_PACKAGE_REGISTRY=OFF -DCMAKE_FIND_USE_PACKAGE_REGISTRY=OFF -DCMAKE_EXPORT_NO_PACKAGE_REGISTRY=ON -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_LOCALEDIR=/nix/store/kaqk1fmxalr5l55ld6hgxq75b1s85qzf-nlohmann_json-3.11.3/share/locale -DCMAKE_INSTALL_LIBEXECDIR=/nix/store/kaqk1fmxalr5l55ld6hgxq75b1s85qzf-nlohmann_json-3.11.3/libexec -DCMAKE_INSTALL_LIBDIR=/nix/store/kaqk1fmxalr5l55ld6hgxq75b1s85qzf-nlohmann_json-3.11.3/lib -DCMAKE_INSTALL_DOCDIR=/nix/store/kaqk1fmxalr5l55ld6hgxq75b1s85qzf-nlohmann_json-3.11.3/share/doc/nlohmann_json -DCMAKE_INSTALL_INFODIR=/nix/store/kaqk1fmxalr5l55ld6hgxq75b1s85qzf-nlohmann_json-3.11.3/share/info -DCMAKE_INSTALL_MANDIR=/nix/store/kaqk1fmxalr5l55ld6hgxq75b1s85qzf-nlohmann_json-3.11.3/share/man -DCMAKE_INSTALL_OLDINCLUDEDIR=/nix/store/kaqk1fmxalr5l55ld6hgxq75b1s85qzf-nlohmann_json-3.11.3/include -DCMAKE_INSTALL_INCLUDEDIR=/nix/store/kaqk1fmxalr5l55ld6hgxq75b1s85qzf-nlohmann_json-3.11.3/include -DCMAKE_INSTALL_SBINDIR=/nix/store/kaqk1fmxalr5l55ld6hgxq75b1s85qzf-nlohmann_json-3.11.3/sbin -DCMAKE_INSTALL_BINDIR=/nix/store/kaqk1fmxalr5l55ld6hgxq75b1s85qzf-nlohmann_json-3.11.3/bin -DCMAKE_INSTALL_NAME_DIR=/nix/store/kaqk1fmxalr5l55ld6hgxq75b1s85qzf-nlohmann_json-3.11.3/lib -DCMAKE_POLICY_DEFAULT_CMP0025=NEW -DCMAKE_FIND_FRAMEWORK=LAST -DCMAKE_STRIP=/nix/store/rr0b7ssq38nvjqm1ski5s840ipv37xvv-clang-wrapper-19.1.1/bin/strip -DCMAKE_RANLIB=/nix/store/rr0b7ssq38nvjqm1ski5s840ipv37xvv-clang-wrapper-19.1.1/bin/ranlib -DCMAKE_AR=/nix/store/rr0b7ssq38nvjqm1ski5s840ipv37xvv-clang-wrapper-19.1.1/bin/ar -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ -DCMAKE_INSTALL_PREFIX=/nix/store/kaqk1fmxalr5l55ld6hgxq75b1s85qzf-nlohmann_json-3.11.3 -DJSON_BuildTests=ON -DJSON_FastTests=ON -DJSON_MultipleHeaders=ON -DJSON_TestDataDirectory=/nix/store/xq70ff8j7f89k1hc0yxz57q9h7qxcvk4-source
-- The CXX compiler identification is Clang 19.1.1
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /nix/store/rr0b7ssq38nvjqm1ski5s840ipv37xvv-clang-wrapper-19.1.1/bin/clang++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Using the multi-header code from /build/source/include/
-- Using test data in /nix/store/xq70ff8j7f89k1hc0yxz57q9h7qxcvk4-source.
-- Operating system: Linux-6.8.0-45-generic; Linux localhost 6.8.0-45-generic #45~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Wed Sep 11 15:25:05 UTC 2 x86_64 GNU/Linux
-- Compiler: clang version 19.1.1; Target: x86_64-unknown-linux-gnu; Thread model: posix; InstalledDir: /nix/store/v4nvxy5xh97n7ds79ig6l9z4pkk1fpv9-clang-19.1.1/bin
-- Testing standards: 11 14 17 20 23
-- Looking for C++ include sys/types.h
-- Looking for C++ include sys/types.h - found
-- Looking for C++ include stdint.h
-- Looking for C++ include stdint.h - found
-- Looking for C++ include stddef.h
-- Looking for C++ include stddef.h - found
-- Check size of size_t
-- Check size of size_t - done
-- Configuring done (0.9s)
-- Generating done (0.1s)
CMake Warning:
  Manually-specified variables were not used by the project:

    CMAKE_C_COMPILER
    CMAKE_EXPORT_NO_PACKAGE_REGISTRY
    CMAKE_FIND_USE_PACKAGE_REGISTRY
    CMAKE_FIND_USE_SYSTEM_PACKAGE_REGISTRY
    CMAKE_POLICY_DEFAULT_CMP0025


-- Build files have been written to: /build/source/build
cmake: enabled parallel building
cmake: enabled parallel installing
Running phase: buildPhase
@nix { "action": "setPhase", "phase": "buildPhase" }
build flags: -j16 SHELL=/nix/store/mm0pa3z7kk6jh1i9rkxqxjqmd8h1qpxf-bash-5.2p37/bin/bash
[  0%] Building CXX object tests/abi/diag/CMakeFiles/abi_compat_diag_off.dir/diag_off.cpp.o
[  1%] Building CXX object tests/CMakeFiles/test_main.dir/src/unit.cpp.o
[  1%] Building CXX object tests/abi/CMakeFiles/abi_compat_main.dir/main.cpp.o
[  1%] Building CXX object tests/abi/diag/CMakeFiles/abi_compat_diag_on.dir/diag_on.cpp.o
[  2%] Linking CXX static library libabi_compat_diag_off.a
[  2%] Built target abi_compat_diag_off
[  3%] Linking CXX static library libabi_compat_diag_on.a
[  3%] Built target abi_compat_diag_on
[  4%] Linking CXX static library libabi_compat_main.a
[  4%] Built target abi_compat_main
[  6%] Building CXX object tests/abi/config/CMakeFiles/abi_config_custom.dir/custom.cpp.o
[  6%] Building CXX object tests/abi/config/CMakeFiles/abi_config_default.dir/default.cpp.o
[  7%] Building CXX object tests/abi/diag/CMakeFiles/abi_compat_diag.dir/diag.cpp.o
[  7%] Built target test_main
[  7%] Building CXX object tests/abi/config/CMakeFiles/abi_config_noversion.dir/noversion.cpp.o
[  8%] Building CXX object tests/abi/inline_ns/CMakeFiles/abi_compat_inline_ns.dir/use_v3_10_5.cpp.o
[  8%] Building CXX object tests/abi/inline_ns/CMakeFiles/abi_compat_inline_ns.dir/use_current.cpp.o
[  9%] Building CXX object tests/CMakeFiles/test-algorithms_cpp11.dir/src/unit-algorithms.cpp.o
[  8%] Building CXX object tests/CMakeFiles/test-allocator_cpp11.dir/src/unit-allocator.cpp.o
[  9%] Building CXX object tests/CMakeFiles/test-assert_macro_cpp11.dir/src/unit-assert_macro.cpp.o
[ 11%] Building CXX object tests/CMakeFiles/test-alt-string_cpp11.dir/src/unit-alt-string.cpp.o
[ 11%] Building CXX object tests/CMakeFiles/test-binary_formats_cpp11.dir/src/unit-binary_formats.cpp.o
[ 11%] Building CXX object tests/CMakeFiles/test-bjdata_cpp11.dir/src/unit-bjdata.cpp.o
[ 11%] Building CXX object tests/CMakeFiles/test-bson_cpp11.dir/src/unit-bson.cpp.o
[ 12%] Building CXX object tests/CMakeFiles/test-byte_container_with_subtype_cpp11.dir/src/unit-byte_container_with_subtype.cpp.o
[ 13%] Building CXX object tests/CMakeFiles/test-capacity_cpp11.dir/src/unit-capacity.cpp.o
[ 14%] Building CXX object tests/CMakeFiles/test-cbor_cpp11.dir/src/unit-cbor.cpp.o
[ 15%] Linking CXX executable abi_compat_diag
[ 15%] Built target abi_compat_diag
In file included from /build/source/tests/src/unit-bson.cpp:9:
In file included from /build/source/tests/thirdparty/doctest/doctest_compatibility.h:6:
In file included from /build/source/tests/thirdparty/doctest/doctest.h:514:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ostream:177:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:24:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ios:561:20: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
  561 |   typedef typename traits_type::int_type int_type;
      |                    ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:40:59: note: in instantiation of template class 'std::basic_ios<unsigned char>' requested here
   40 | class _LIBCPP_TEMPLATE_VIS basic_ostream : virtual public basic_ios<_CharT, _Traits> {
      |                                                           ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/sstream:986:57: note: in instantiation of template class 'std::basic_ostream<unsigned char>' requested here
  986 | class _LIBCPP_TEMPLATE_VIS basic_ostringstream : public basic_ostream<_CharT, _Traits> {
      |                                                         ^
/build/source/tests/src/unit-bson.cpp:624:52: note: in instantiation of template class 'std::basic_ostringstream<unsigned char>' requested here
  624 |             std::basic_ostringstream<std::uint8_t> ss;
      |                                                    ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-bson.cpp:9:
In file included from /build/source/tests/thirdparty/doctest/doctest_compatibility.h:6:
In file included from /build/source/tests/thirdparty/doctest/doctest.h:514:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ostream:177:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:24:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ios:562:20: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
  562 |   typedef typename traits_type::pos_type pos_type;
      |                    ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-bson.cpp:9:
In file included from /build/source/tests/thirdparty/doctest/doctest_compatibility.h:6:
In file included from /build/source/tests/thirdparty/doctest/doctest.h:514:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ostream:177:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:24:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ios:563:20: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
  563 |   typedef typename traits_type::off_type off_type;
      |                    ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-bson.cpp:9:
In file included from /build/source/tests/thirdparty/doctest/doctest_compatibility.h:6:
In file included from /build/source/tests/thirdparty/doctest/doctest.h:514:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ostream:177:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:24:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ios:565:42: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
  565 |   static_assert(is_same<_CharT, typename traits_type::char_type>::value,
      |                                          ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-bson.cpp:9:
In file included from /build/source/tests/thirdparty/doctest/doctest_compatibility.h:6:
In file included from /build/source/tests/thirdparty/doctest/doctest.h:514:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ostream:177:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:24:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ios:543:64: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
  543 |   _LIBCPP_HIDE_FROM_ABI _SentinelValueFill& operator=(typename _Traits::int_type __x) {
      |                                                                ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ios:629:21: note: in instantiation of template class 'std::_SentinelValueFill<std::char_traits<unsigned char>>' requested here
  629 |   mutable _FillType __fill_;
      |                     ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:40:59: note: in instantiation of template class 'std::basic_ios<unsigned char>' requested here
   40 | class _LIBCPP_TEMPLATE_VIS basic_ostream : virtual public basic_ios<_CharT, _Traits> {
      |                                                           ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/sstream:986:57: note: in instantiation of template class 'std::basic_ostream<unsigned char>' requested here
  986 | class _LIBCPP_TEMPLATE_VIS basic_ostringstream : public basic_ostream<_CharT, _Traits> {
      |                                                         ^
/build/source/tests/src/unit-bson.cpp:624:52: note: in instantiation of template class 'std::basic_ostringstream<unsigned char>' requested here
  624 |             std::basic_ostringstream<std::uint8_t> ss;
      |                                                    ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-bson.cpp:9:
In file included from /build/source/tests/thirdparty/doctest/doctest_compatibility.h:6:
In file included from /build/source/tests/thirdparty/doctest/doctest.h:514:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ostream:177:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:24:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ios:548:34: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
  548 |   _LIBCPP_HIDE_FROM_ABI typename _Traits::int_type __get() const { return __fill_val_; }
      |                                  ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-bson.cpp:9:
In file included from /build/source/tests/thirdparty/doctest/doctest_compatibility.h:6:
In file included from /build/source/tests/thirdparty/doctest/doctest.h:514:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ostream:177:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:24:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ios:551:12: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
  551 |   typename _Traits::int_type __fill_val_;
      |            ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-bson.cpp:9:
In file included from /build/source/tests/thirdparty/doctest/doctest_compatibility.h:6:
In file included from /build/source/tests/thirdparty/doctest/doctest.h:514:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ostream:177:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:45:20: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
   45 |   typedef typename traits_type::int_type int_type;
      |                    ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/sstream:986:57: note: in instantiation of template class 'std::basic_ostream<unsigned char>' requested here
  986 | class _LIBCPP_TEMPLATE_VIS basic_ostringstream : public basic_ostream<_CharT, _Traits> {
      |                                                         ^
/build/source/tests/src/unit-bson.cpp:624:52: note: in instantiation of template class 'std::basic_ostringstream<unsigned char>' requested here
  624 |             std::basic_ostringstream<std::uint8_t> ss;
      |                                                    ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-bson.cpp:9:
In file included from /build/source/tests/thirdparty/doctest/doctest_compatibility.h:6:
In file included from /build/source/tests/thirdparty/doctest/doctest.h:514:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ostream:177:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:46:20: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
   46 |   typedef typename traits_type::pos_type pos_type;
      |                    ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-bson.cpp:9:
In file included from /build/source/tests/thirdparty/doctest/doctest_compatibility.h:6:
In file included from /build/source/tests/thirdparty/doctest/doctest.h:514:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ostream:177:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:47:20: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
   47 |   typedef typename traits_type::off_type off_type;
      |                    ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-bson.cpp:9:
In file included from /build/source/tests/thirdparty/doctest/doctest_compatibility.h:6:
In file included from /build/source/tests/thirdparty/doctest/doctest.h:514:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ostream:177:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:53:20: error: only virtual member functions can be marked 'override'
   53 |   ~basic_ostream() override;
      |                    ^
In file included from /build/source/tests/src/unit-bson.cpp:16:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/sstream:990:20: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
  990 |   typedef typename traits_type::int_type int_type;
      |                    ^
/build/source/tests/src/unit-bson.cpp:624:52: note: in instantiation of template class 'std::basic_ostringstream<unsigned char>' requested here
  624 |             std::basic_ostringstream<std::uint8_t> ss;
      |                                                    ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-bson.cpp:16:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/sstream:991:20: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
  991 |   typedef typename traits_type::pos_type pos_type;
      |                    ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-bson.cpp:16:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/sstream:992:20: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
  992 |   typedef typename traits_type::off_type off_type;
      |                    ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-bson.cpp:9:
In file included from /build/source/tests/thirdparty/doctest/doctest_compatibility.h:6:
In file included from /build/source/tests/thirdparty/doctest/doctest.h:514:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ostream:177:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:25:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/locale:215:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/streambuf:136:20: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
  136 |   typedef typename traits_type::int_type int_type;
      |                    ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/sstream:337:53: note: in instantiation of template class 'std::basic_streambuf<unsigned char>' requested here
  337 | class _LIBCPP_TEMPLATE_VIS basic_stringbuf : public basic_streambuf<_CharT, _Traits> {
      |                                                     ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/sstream:998:59: note: in instantiation of template class 'std::basic_stringbuf<unsigned char>' requested here
  998 |   basic_stringbuf<char_type, traits_type, allocator_type> __sb_;
      |                                                           ^
/build/source/tests/src/unit-bson.cpp:624:52: note: in instantiation of template class 'std::basic_ostringstream<unsigned char>' requested here
  624 |             std::basic_ostringstream<std::uint8_t> ss;
      |                                                    ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-bson.cpp:9:
In file included from /build/source/tests/thirdparty/doctest/doctest_compatibility.h:6:
In file included from /build/source/tests/thirdparty/doctest/doctest.h:514:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ostream:177:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:25:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/locale:215:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/streambuf:137:20: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
  137 |   typedef typename traits_type::pos_type pos_type;
      |                    ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | [ 15%] Building CXX object tests/CMakeFiles/test-class_const_iterator_cpp11.dir/src/unit-class_const_iterator.cpp.o
struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-bson.cpp:9:
In file included from /build/source/tests/thirdparty/doctest/doctest_compatibility.h:6:
In file included from /build/source/tests/thirdparty/doctest/doctest.h:514:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ostream:177:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:25:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/locale:215:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/streambuf:138:20: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
  138 |   typedef typename traits_type::off_type off_type;
      |                    ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-bson.cpp:9:
In file included from /build/source/tests/thirdparty/doctest/doctest_compatibility.h:6:
In file included from /build/source/tests/thirdparty/doctest/doctest.h:514:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ostream:177:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:25:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/locale:215:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/streambuf:140:42: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
  140 |   static_assert(is_same<_CharT, typename traits_type::char_type>::value,
      |                                          ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-bson.cpp:16:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/sstream:341:20: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
  341 |   typedef typename traits_type::int_type int_type;
      |                    ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/sstream:998:59: note: in instantiation of template class 'std::basic_stringbuf<unsigned char>' requested here
  998 |   basic_stringbuf<char_type, traits_type, allocator_type> __sb_;
      |                                                           ^
/build/source/tests/src/unit-bson.cpp:624:52: note: in instantiation of template class 'std::basic_ostringstream<unsigned char>' requested here
  624 |             std::basic_ostringstream<std::uint8_t> ss;
      |                                                    ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
20 errors generated.
make[2]: *** [tests/CMakeFiles/test-bson_cpp11.dir/build.make:76: tests/CMakeFiles/test-bson_cpp11.dir/src/unit-bson.cpp.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:1399: tests/CMakeFiles/test-bson_cpp11.dir/all] Error 2
make[1]: *** Waiting for unfinished jobs....
[ 15%] Linking CXX executable abi_config_custom
[ 15%] Built target abi_config_custom
[ 15%] Linking CXX executable test-assert_macro_cpp11
[ 15%] Built target test-assert_macro_cpp11
In file included from /build/source/tests/src/unit-cbor.cpp:9:
In file included from /build/source/tests/thirdparty/doctest/doctest_compatibility.h:6:
In file included from /build/source/tests/thirdparty/doctest/doctest.h:514:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ostream:177:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:24:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ios:561:20: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
  561 |   typedef typename traits_type::int_type int_type;
      |                    ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:40:59: note: in instantiation of template class 'std::basic_ios<unsigned char>' requested here
   40 | class _LIBCPP_TEMPLATE_VIS basic_ostream : virtual public basic_ios<_CharT, _Traits> {
      |                                                           ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/sstream:986:57: note: in instantiation of template class 'std::basic_ostream<unsigned char>' requested here
  986 | class _LIBCPP_TEMPLATE_VIS basic_ostringstream : public basic_ostream<_CharT, _Traits> {
      |                                                         ^
/build/source/tests/src/unit-cbor.cpp:1884:56: note: in instantiation of template class 'std::basic_ostringstream<unsigned char>' requested here
 1884 |                 std::basic_ostringstream<std::uint8_t> ss;
      |                                                        ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-cbor.cpp:9:
In file included from /build/source/tests/thirdparty/doctest/doctest_compatibility.h:6:
In file included from /build/source/tests/thirdparty/doctest/doctest.h:514:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ostream:177:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:24:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ios:562:20: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
  562 |   typedef typename traits_type::pos_type pos_type;
      |                    ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-cbor.cpp:9:
In file included from /build/source/tests/thirdparty/doctest/doctest_compatibility.h:6:
In file included from /build/source/tests/thirdparty/doctest/doctest.h:514:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ostream:177:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:24:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ios:563:20: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
  563 |   typedef typename traits_type::off_type off_type;
      |                    ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-cbor.cpp:9:
In file included from /build/source/tests/thirdparty/doctest/doctest_compatibility.h:6:
In file included from /build/source/tests/thirdparty/doctest/doctest.h:514:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ostream:177:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:24:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ios:565:42: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
  565 |   static_assert(is_same<_CharT, typename traits_type::char_type>::value,
      |                                          ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-cbor.cpp:9:
In file included from /build/source/tests/thirdparty/doctest/doctest_compatibility.h:6:
In file included from /build/source/tests/thirdparty/doctest/doctest.h:514:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ostream:177:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:24:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ios:543:64: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
  543 |   _LIBCPP_HIDE_FROM_ABI _SentinelValueFill& operator=(typename _Traits::int_type __x) {
      |                                                                ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ios:629:21: note: in instantiation of template class 'std::_SentinelValueFill<std::char_traits<unsigned char>>' requested here
  629 |   mutable _FillType __fill_;
      |                     ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:40:59: note: in instantiation of template class 'std::basic_ios<unsigned char>' requested here
   40 | class _LIBCPP_TEMPLATE_VIS basic_ostream : virtual public basic_ios<_CharT, _Traits> {
      |                                                           ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/sstream:986:57: note: in instantiation of template class 'std::basic_ostream<unsigned char>' requested here
  986 | class _LIBCPP_TEMPLATE_VIS basic_ostringstream : public basic_ostream<_CharT, _Traits> {
      |                                                         ^
/build/source/tests/src/unit-cbor.cpp:1884:56: note: in instantiation of template class 'std::basic_ostringstream<unsigned char>' requested here
 1884 |                 std::basic_ostringstream<std::uint8_t> ss;
      |                                                        ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-cbor.cpp:9:
In file included from /build/source/tests/thirdparty/doctest/doctest_compatibility.h:6:
In file included from /build/source/tests/thirdparty/doctest/doctest.h:514:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ostream:177:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:24:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ios:548:34: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
  548 |   _LIBCPP_HIDE_FROM_ABI typename _Traits::int_type __get() const { return __fill_val_; }
      |                                  ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-cbor.cpp:9:
In file included from /build/source/tests/thirdparty/doctest/doctest_compatibility.h:6:
In file included from /build/source/tests/thirdparty/doctest/doctest.h:514:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ostream:177:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:24:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ios:551:12: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
  551 |   typename _Traits::int_type __fill_val_;
      |            ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-cbor.cpp:9:
In file included from /build/source/tests/thirdparty/doctest/doctest_compatibility.h:6:
In file included from /build/source/tests/thirdparty/doctest/doctest.h:514:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ostream:177:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:45:20: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
   45 |   typedef typename traits_type::int_type int_type;
      |                    ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/sstream:986:57: note: in instantiation of template class 'std::basic_ostream<unsigned char>' requested here
  986 | class _LIBCPP_TEMPLATE_VIS basic_ostringstream : public basic_ostream<_CharT, _Traits> {
      |                                                         ^
/build/source/tests/src/unit-cbor.cpp:1884:56: note: in instantiation of template class 'std::basic_ostringstream<unsigned char>' requested here
 1884 |                 std::basic_ostringstream<std::uint8_t> ss;
      |                                                        ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-cbor.cpp:9:
In file included from /build/source/tests/thirdparty/doctest/doctest_compatibility.h:6:
In file included from /build/source/tests/thirdparty/doctest/doctest.h:514:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ostream:177:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:46:20: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
   46 |   typedef typename traits_type::pos_type pos_type;
      |                    ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-cbor.cpp:9:
In file included from /build/source/tests/thirdparty/doctest/doctest_compatibility.h:6:
In file included from /build/source/tests/thirdparty/doctest/doctest.h:514:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ostream:177:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:47:20: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
   47 |   typedef typename traits_type::off_type off_type;
      |                    ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-cbor.cpp:9:
In file included from /build/source/tests/thirdparty/doctest/doctest_compatibility.h:6:
In file included from /build/source/tests/thirdparty/doctest/doctest.h:514:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ostream:177:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:53:20: error: only virtual member functions can be marked 'override'
   53 |   ~basic_ostream() override;
      |                    ^
In file included from /build/source/tests/src/unit-cbor.cpp:15:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/sstream:990:20: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
  990 |   typedef typename traits_type::int_type int_type;
      |                    ^
/build/source/tests/src/unit-cbor.cpp:1884:56: note: in instantiation of template class 'std::basic_ostringstream<unsigned char>' requested here
 1884 |                 std::basic_ostringstream<std::uint8_t> ss;
      |                                                        ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-cbor.cpp:15:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/sstream:991:20: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
  991 |   typedef typename traits_type::pos_type pos_type;
      |                    ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-cbor.cpp:15:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/sstream:992:20: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
  992 |   typedef typename traits_type::off_type off_type;
      |                    ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-cbor.cpp:9:
In file included from /build/source/tests/thirdparty/doctest/doctest_compatibility.h:6:
In file included from /build/source/tests/thirdparty/doctest/doctest.h:514:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ostream:177:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:25:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/locale:215:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/streambuf:136:20: error: [ 15%] Linking CXX executable test-byte_container_with_subtype_cpp11
implicit instantiation of undefined template 'std::char_traits<unsigned char>'
  136 |   typedef typename traits_type::int_type int_type;
      |                    ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/sstream:337:53: note: in instantiation of template class 'std::basic_streambuf<unsigned char>' requested here
  337 | class _LIBCPP_TEMPLATE_VIS basic_stringbuf : public basic_streambuf<_CharT, _Traits> {
      |                                                     ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/sstream:998:59: note: in instantiation of template class 'std::basic_stringbuf<unsigned char>' requested here
  998 |   basic_stringbuf<char_type, traits_type, allocator_type> __sb_;
      |                                                           ^
/build/source/tests/src/unit-cbor.cpp:1884:56: note: in instantiation of template class 'std::basic_ostringstream<unsigned char>' requested here
 1884 |                 std::basic_ostringstream<std::uint8_t> ss;
      |                                                        ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-cbor.cpp:9:
In file included from /build/source/tests/thirdparty/doctest/doctest_compatibility.h:6:
In file included from /build/source/tests/thirdparty/doctest/doctest.h:514:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ostream:177:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:25:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/locale:215:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/streambuf:137:20: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
  137 |   typedef typename traits_type::pos_type pos_type;
      |                    ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-cbor.cpp:9:
In file included from /build/source/tests/thirdparty/doctest/doctest_compatibility.h:6:
In file included from /build/source/tests/thirdparty/doctest/doctest.h:514:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ostream:177:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:25:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/locale:215:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/streambuf:138:20: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
  138 |   typedef typename traits_type::off_type off_type;
      |                    ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-cbor.cpp:9:
In file included from /build/source/tests/thirdparty/doctest/doctest_compatibility.h:6:
In file included from /build/source/tests/thirdparty/doctest/doctest.h:514:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/ostream:177:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__ostream/basic_ostream.h:25:
In file included from /nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/locale:215:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/streambuf:140:42: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
  140 |   static_assert(is_same<_CharT, typename traits_type::char_type>::value,
      |                                          ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
In file included from /build/source/tests/src/unit-cbor.cpp:15:
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/sstream:341:20: error: implicit instantiation of undefined template 'std::char_traits<unsigned char>'
  341 |   typedef typename traits_type::int_type int_type;
      |                    ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/sstream:998:59: note: in instantiation of template class 'std::basic_stringbuf<unsigned char>' requested here
  998 |   basic_stringbuf<char_type, traits_type, allocator_type> __sb_;
      |                                                           ^
/build/source/tests/src/unit-cbor.cpp:1884:56: note: in instantiation of template class 'std::basic_ostringstream<unsigned char>' requested here
 1884 |                 std::basic_ostringstream<std::uint8_t> ss;
      |                                                        ^
/nix/store/rfmv7mz9bn2l6r7gy4cvpqawjws1d6jl-libcxx-19.1.1-dev/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
   23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
      |                             ^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
20 errors generated.
make[2]: *** [tests/CMakeFiles/test-cbor_cpp11.dir/build.make:76: tests/CMakeFiles/test-cbor_cpp11.dir/src/unit-cbor.cpp.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:1477: tests/CMakeFiles/test-cbor_cpp11.dir/all] Error 2
[ 15%] Built target test-byte_container_with_subtype_cpp11
[ 15%] Linking CXX executable abi_config_default
[ 15%] Built target abi_config_default
[ 16%] Linking CXX executable abi_config_noversion
[ 16%] Built target abi_config_noversion
[ 17%] Linking CXX executable abi_compat_inline_ns
[ 17%] Built target abi_compat_inline_ns
[ 17%] Linking CXX executable test-capacity_cpp11
[ 17%] Built target test-capacity_cpp11
[ 18%] Linking CXX executable test-allocator_cpp11
[ 18%] Built target test-allocator_cpp11
[ 19%] Linking CXX executable test-class_const_iterator_cpp11
[ 19%] Built target test-class_const_iterator_cpp11
[ 20%] Linking CXX executable test-binary_formats_cpp11
[ 20%] Built target test-binary_formats_cpp11
[ 20%] Linking CXX executable test-alt-string_cpp11
[ 20%] Built target test-alt-string_cpp11
[ 21%] Linking CXX executable test-algorithms_cpp11
[ 21%] Built target test-algorithms_cpp11
[ 22%] Linking CXX executable test-bjdata_cpp11
[ 22%] Built target test-bjdata_cpp11
make: *** [Makefile:146: all] Error 2

Compiler and operating system

clang-19 w/ libc++ on ubuntu using nix-shell

Library version

3.1.0 and the HEAD of develop

Validation

• The bug also occurs if the latest version from the develop branch is used.
• I can successfully compile and run the unit tests.

[paparodeo]

this diff will make the tests compile for clang-19 by removing unsupported types.

diff --git a/tests/src/unit-bson.cpp b/tests/src/unit-bson.cpp
index 13216f2..fdfc350 100644
--- a/tests/src/unit-bson.cpp
+++ b/tests/src/unit-bson.cpp
@@ -621,7 +621,7 @@ TEST_CASE("BSON input/output_adapters")
     {
         SECTION("std::ostringstream")
         {
-            std::basic_ostringstream<std::uint8_t> ss;
+            std::basic_ostringstream<char> ss;
             json::to_bson(json_representation, ss);
             json j3 = json::from_bson(ss.str());
             CHECK(json_representation == j3);
diff --git a/tests/src/unit-cbor.cpp b/tests/src/unit-cbor.cpp
index be94d2f..2b396b7 100644
--- a/tests/src/unit-cbor.cpp
+++ b/tests/src/unit-cbor.cpp
@@ -1881,7 +1881,7 @@ TEST_CASE("single CBOR roundtrip")
         {
             SECTION("std::ostringstream")
             {
-                std::basic_ostringstream<std::uint8_t> ss;
+                std::basic_ostringstream<char> ss;
                 json::to_cbor(j1, ss);
                 json j3 = json::from_cbor(ss.str());
                 CHECK(j1 == j3);
diff --git a/tests/src/unit-deserialization.cpp b/tests/src/unit-deserialization.cpp
index 3bc161f..e4918b0 100644
--- a/tests/src/unit-deserialization.cpp
+++ b/tests/src/unit-deserialization.cpp
@@ -1131,13 +1131,11 @@ TEST_CASE("deserialization")
     }
 }
 
+
 TEST_CASE_TEMPLATE("deserialization of different character types (ASCII)", T,
-                   char, unsigned char, signed char,
+                   char,
                    wchar_t,
-                   char16_t, char32_t,
-                   std::uint8_t, std::int8_t,
-                   std::int16_t, std::uint16_t,
-                   std::int32_t, std::uint32_t)
+                   char16_t, char32_t)
 {
     std::vector<T> const v = {'t', 'r', 'u', 'e'};
     CHECK(json::parse(v) == json(true));
@@ -1163,7 +1161,7 @@ TEST_CASE_TEMPLATE("deserialization of different character types (UTF-8)", T,
 }
 
 TEST_CASE_TEMPLATE("deserialization of different character types (UTF-16)", T,
-                   char16_t, std::uint16_t)
+                   char16_t)
 {
     // a star emoji
     std::vector<T> const v = {static_cast<T>('"'), static_cast<T>(0x2b50), static_cast<T>(0xfe0f), static_cast<T>('"')};
@@ -1176,7 +1174,7 @@ TEST_CASE_TEMPLATE("deserialization of different character types (UTF-16)", T,
 }
 
 TEST_CASE_TEMPLATE("deserialization of different character types (UTF-32)", T,
-                   char32_t, std::uint32_t)
+                   char32_t)
 {
     // a star emoji
     std::vector<T> const v = {static_cast<T>('"'), static_cast<T>(0x2b50), static_cast<T>(0xfe0f), static_cast<T>('"')};
diff --git a/tests/src/unit-msgpack.cpp b/tests/src/unit-msgpack.cpp
index 61162af..cfbb1fa 100644
--- a/tests/src/unit-msgpack.cpp
+++ b/tests/src/unit-msgpack.cpp
@@ -1604,7 +1604,7 @@ TEST_CASE("single MessagePack roundtrip")
         {
             SECTION("std::ostringstream")
             {
-                std::basic_ostringstream<std::uint8_t> ss;
+                std::basic_ostringstream<char> ss;
                 json::to_msgpack(j1, ss);
                 json j3 = json::from_msgpack(ss.str());
                 CHECK(j1 == j3);
diff --git a/tests/src/unit-regression2.cpp b/tests/src/unit-regression2.cpp
index fab9aae..98947c5 100644
--- a/tests/src/unit-regression2.cpp
+++ b/tests/src/unit-regression2.cpp
@@ -674,6 +674,7 @@ TEST_CASE("regression tests 2")
         CHECK(j.dump() == "{}");
     }
 
+#if 0
 #ifdef JSON_HAS_CPP_20
 #if __has_include(<span>)
     SECTION("issue #2546 - parsing containers of std::byte")
@@ -684,6 +685,7 @@ TEST_CASE("regression tests 2")
         CHECK(j.dump() == "\"Hello, world!\"");
     }
 #endif
+#endif
 #endif
 
     SECTION("issue #2574 - Deserialization to std::array, std::pair, and std::tuple with non-default constructable types fails")

[nlohmann]

Thanks for reporting. We really need a CI runner for clang+libc++ to detect this ourselves...

[nlohmann]

With #4495, I can reproduce the issue.

[jeffmelville]

FWIW the example in the readme still uses std::vector<uint8_t> which I think would be impacted by this bug. Right?