From dc9e22940a0febaa989c4a4a57cd3f41be8d12c9 Mon Sep 17 00:00:00 2001
From: Enrico Seiler <enrico.seiler@hotmail.de>
Date: Mon, 13 Nov 2023 11:59:40 +0100
Subject: [PATCH 1/2] [FIX] libc++: header tests

---
 include/seqan3/core/debug_stream/debug_stream_type.hpp | 2 +-
 include/seqan3/utility/simd/detail/builtin_simd.hpp    | 2 +-
 test/header/CMakeLists.txt                             | 7 +++++--
 test/include/seqan3/test/pretty_printing.hpp           | 1 +
 test/seqan3-test.cmake                                 | 2 ++
 5 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/include/seqan3/core/debug_stream/debug_stream_type.hpp b/include/seqan3/core/debug_stream/debug_stream_type.hpp
index 9dae4e382f..2671f49df8 100644
--- a/include/seqan3/core/debug_stream/debug_stream_type.hpp
+++ b/include/seqan3/core/debug_stream/debug_stream_type.hpp
@@ -155,7 +155,7 @@ class debug_stream_type
     //!\}
 
     //!\brief This type is std::ios_base::fmtflags
-    using fmtflags = decltype(std::declval<std::basic_ostream<char_t>>().flags());
+    using fmtflags = typename std::basic_ostream<char_t>::fmtflags;
 
     /*!\name Format flags (std::ios_base::fmtflags)
      * \brief std::ios_base::fmtflags that modify the stream's behaviour.
diff --git a/include/seqan3/utility/simd/detail/builtin_simd.hpp b/include/seqan3/utility/simd/detail/builtin_simd.hpp
index bd1f8bbf33..dc92928b81 100644
--- a/include/seqan3/utility/simd/detail/builtin_simd.hpp
+++ b/include/seqan3/utility/simd/detail/builtin_simd.hpp
@@ -134,7 +134,7 @@ constexpr bool is_builtin_simd_v = is_builtin_simd<builtin_simd_t>::value;
  * seqan3::detail::builtin_simd types.
  */
 template <>
-constexpr auto default_simd_max_length<builtin_simd> = []()
+inline constexpr auto default_simd_max_length<builtin_simd> = []()
 {
 #if defined(__AVX512F__)
     return min_viable_uint_v<64u>;
diff --git a/test/header/CMakeLists.txt b/test/header/CMakeLists.txt
index d28ade8a93..5bfab0be52 100644
--- a/test/header/CMakeLists.txt
+++ b/test/header/CMakeLists.txt
@@ -84,7 +84,7 @@ macro (seqan3_header_test component header_base_path exclude_regex)
 
     file (WRITE "${PROJECT_BINARY_DIR}/${target}.cpp" "")
     add_executable (${target} ${PROJECT_BINARY_DIR}/${target}.cpp)
-    target_link_libraries (${target} seqan3::test::header)
+    target_link_libraries (${target} seqan3::test seqan3::test::header)
     add_test (NAME "header/${target}" COMMAND ${target})
 
     foreach (header ${header_files})
@@ -112,7 +112,10 @@ macro (seqan3_header_test component header_base_path exclude_regex)
                                         "${CMAKE_CURRENT_SOURCE_DIR}/generate_header_source.cmake")
 
             add_library (${header_target} OBJECT "${header_target_source}")
-            target_link_libraries (${header_target} seqan3::test::header)
+            # Link seqan3::test first, even though it is also linked by seqan3::test:header.
+            # Without this, the compile options of seqan3::test are appended, e.g.,
+            # `-Wno-error=... -Werror -Wall`, instead of `-Werror -Wall -Wno-error=...`
+            target_link_libraries (${header_target} seqan3::test seqan3::test::header)
             target_sources (${target} PRIVATE $<TARGET_OBJECTS:${header_target}>)
         endforeach ()
     endforeach ()
diff --git a/test/include/seqan3/test/pretty_printing.hpp b/test/include/seqan3/test/pretty_printing.hpp
index e929106309..bb95f2e311 100644
--- a/test/include/seqan3/test/pretty_printing.hpp
+++ b/test/include/seqan3/test/pretty_printing.hpp
@@ -14,6 +14,7 @@
 
 #include <ios>
 #include <iterator>
+#include <ostream>
 
 #include <seqan3/core/debug_stream/debug_stream_type.hpp>
 
diff --git a/test/seqan3-test.cmake b/test/seqan3-test.cmake
index 7f35f13ff2..f19dc33f4a 100644
--- a/test/seqan3-test.cmake
+++ b/test/seqan3-test.cmake
@@ -120,6 +120,8 @@ if (NOT TARGET seqan3::test::header)
     add_library (seqan3_test_header INTERFACE)
     target_link_libraries (seqan3_test_header INTERFACE "seqan3::test::unit")
     target_link_libraries (seqan3_test_header INTERFACE "seqan3::test::performance")
+    target_compile_options (seqan3_test_header INTERFACE "-Wno-unused-const-variable" "-Wno-unused-variable"
+                                                         "-Wno-unused-function")
     target_compile_definitions (seqan3_test_header INTERFACE -DSEQAN3_DISABLE_DEPRECATED_WARNINGS)
     target_compile_definitions (seqan3_test_header INTERFACE -DSEQAN3_HEADER_TEST)
     add_library (seqan3::test::header ALIAS seqan3_test_header)

From b447e2f67b2cda785e3955ecd5e40179f0d0632c Mon Sep 17 00:00:00 2001
From: Enrico Seiler <enrico.seiler@hotmail.de>
Date: Mon, 13 Nov 2023 12:01:26 +0100
Subject: [PATCH 2/2] [INFRA] Add libc++ header test CI

---
 .github/workflows/ci_misc.yml | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/.github/workflows/ci_misc.yml b/.github/workflows/ci_misc.yml
index df98a2459a..0cd25de316 100644
--- a/.github/workflows/ci_misc.yml
+++ b/.github/workflows/ci_misc.yml
@@ -43,6 +43,13 @@ jobs:
             build_type: Release
             test_threads: 2
 
+          - name: "Header clang17 libc++"
+            compiler: "clang-17"
+            build: header
+            build_type: Release
+            test_threads: 2
+            cxx_flags: "-stdlib=libc++"
+
           - name: "Header gcc13"
             compiler: "gcc-13"
             build: header