warning: circular header file dependency detected while including 'base.h'

[ClausKlein]

I use

#==================================================
project(
    fmt
    VERSION 12.1.0.1
    DESCRIPTION "A modern formatting library"
    HOMEPAGE_URL https://fmt.dev/12.0/
    LANGUAGES CXX
)
#==================================================

Which this example:

// Header-only configuration test

#ifdef FMT_MODULE

#  ifdef FMT_IMPORT_STD
import std;
import std.compat;
#  else
#    include <string_view>
#  endif

import fmt;

#else

#  include "fmt/base.h"
#  include "fmt/ostream.h"

#endif

// NOLINTNEXTLINE(bugprone-exception-escape)
auto main() -> int
{
  constexpr std::string_view text {"constexpr"};
  fmt::print(text);
}

I got this clang-tidy errors:

Running clang-tidy for 1 files out of 31 in compilation database ...
[1/1][14.9s] /usr/local/Cellar/llvm/21.1.6/bin/clang-tidy -p=/Users/clausklein/Workspace/cpp/cxx20/fmt-module /Users/clausklein/Workspace/cpp/cxx20/fmt-module/tests/header-only-test.cc
error: missing '(' after '__has_feature' [clang-diagnostic-error]
/Users/clausklein/.cache/CPM/fmt/6226dc0d560c5dca8bcd81db09f7e2752ccb8cef/include/fmt/format.h:41:10: warning: circular header file dependency detected while including 'base.h', please check the include path [misc-header-include-cycle]
   41 | #include "base.h"
      |          ^
/Users/clausklein/.cache/CPM/fmt/6226dc0d560c5dca8bcd81db09f7e2752ccb8cef/include/fmt/base.h:3008:12: note: 'format.h' included from here
 3008 | #  include "format.h"
      |            ^
/Users/clausklein/Workspace/cpp/cxx20/fmt-module/tests/header-only-test.cc:16:12: note: 'base.h' included from here
   16 | #  include "fmt/base.h"
      |            ^
122455 warnings and 10 errors generated.
Error while processing /Users/clausklein/Workspace/cpp/cxx20/fmt-module/tests/header-only-test.cc.
Suppressed 122458 warnings (122454 in non-user code, 4 NOLINT).
Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
Found compiler error(s).

bash-5.3$ 

[ClausKlein]

How it is build:

bash-5.3$ ninja -C build
ninja: Entering directory `build'
[0/2] Re-checking globbed directories...
[1/2] Re-running CMake...
-- use ccache
-- CPM: Adding package fmt@12.1.0 (12.1.0 at /Users/clausklein/.cache/CPM/fmt/6226dc0d560c5dca8bcd81db09f7e2752ccb8cef)
CMake Warning at CMakeLists.txt:223 (message):
  Missing or disabled support for CXX_MODULES!


-- Configuring done (1.0s)
-- Generating done (0.2s)
-- Build files have been written to: /Users/clausklein/Workspace/cpp/cxx20/fmt-module/build
[0/4] Re-checking globbed directories...
[5/8] Linking CXX executable tests/header-only-test
bash-5.3$ ninja -C build clean
ninja: Entering directory `build'
[0/2] Re-checking globbed directories...
[1/2] Cleaning all built files...
Cleaning... 5 files.
bash-5.3$ ninja -C build -v
ninja: Entering directory `build'
[0/2] /usr/local/bin/cmake -P /Users/clausklein/Workspace/cpp/cxx20/fmt-module/build/CMakeFiles/VerifyGlobs.cmake
[1/6] /usr/local/bin/ccache /usr/local/Cellar/llvm/21.1.6/bin/clang++ -DFMT_USE_FCNTL=0 -Dfmt_EXPORTS -I/Users/clausklein/.cache/CPM/fmt/6226dc0d560c5dca8bcd81db09f7e2752ccb8cef/include -O3 -DNDEBUG -std=gnu++23 -fPIC -MD -MT CMakeFiles/fmt.dir/module/format.cc.o -MF CMakeFiles/fmt.dir/module/format.cc.o.d -o CMakeFiles/fmt.dir/module/format.cc.o -c /Users/clausklein/Workspace/cpp/cxx20/fmt-module/module/format.cc
[2/6] /usr/local/bin/ccache /usr/local/Cellar/llvm/21.1.6/bin/clang++ -DFMT_USE_FCNTL=0 -Dfmt_EXPORTS -I/Users/clausklein/.cache/CPM/fmt/6226dc0d560c5dca8bcd81db09f7e2752ccb8cef/include -O3 -DNDEBUG -std=gnu++23 -fPIC -MD -MT CMakeFiles/fmt.dir/module/os.cc.o -MF CMakeFiles/fmt.dir/module/os.cc.o.d -o CMakeFiles/fmt.dir/module/os.cc.o -c /Users/clausklein/Workspace/cpp/cxx20/fmt-module/module/os.cc
[3/6] /usr/local/bin/ccache /usr/local/Cellar/llvm/21.1.6/bin/clang++ -DFMT_HEADER_ONLY -I/Users/clausklein/.cache/CPM/fmt/6226dc0d560c5dca8bcd81db09f7e2752ccb8cef/include -O3 -DNDEBUG -std=gnu++23 -MD -MT tests/CMakeFiles/header-only-test.dir/header-only-test.cc.o -MF tests/CMakeFiles/header-only-test.dir/header-only-test.cc.o.d -o tests/CMakeFiles/header-only-test.dir/header-only-test.cc.o -c /Users/clausklein/Workspace/cpp/cxx20/fmt-module/tests/header-only-test.cc
[4/6] : && /usr/local/Cellar/llvm/21.1.6/bin/clang++ -O3 -DNDEBUG  -dynamiclib -Wl,-headerpad_max_install_names -o libfmt.dylib -install_name @rpath/libfmt.dylib CMakeFiles/fmt.dir/module/format.cc.o CMakeFiles/fmt.dir/module/os.cc.o   && :
[5/6] : && /usr/local/Cellar/llvm/21.1.6/bin/clang++ -O3 -DNDEBUG -Wl,-search_paths_first -Wl,-headerpad_max_install_names tests/CMakeFiles/header-only-test.dir/header-only-test.cc.o -o tests/header-only-test   && :
bash-5.3$ 

bash-5.3$ ninja -C build test
ninja: Entering directory `build'
[0/2] Re-checking globbed directories...
[0/2] Running tests...
Test project /Users/clausklein/Workspace/cpp/cxx20/fmt-module/build
    Start 1: find-package-test
1/2 Test #1: find-package-test ................   Passed    3.29 sec
    Start 2: header-only-test
2/2 Test #2: header-only-test .................   Passed    0.29 sec

100% tests passed, 0 tests failed out of 2

Total Test time (real) =   3.58 sec
bash-5.3$