I was trying to "modernise" my CMake files, but it didn't go very well!

I have the following `CMake` file:

Code:

---

cmake_minimum_required(VERSION 3.19...3.25 FATAL_ERROR)

project(
        Turingforge
        VERSION 0.1.0
        DESCRIPTION "Hardware powered Symbolic Regression library."
        HOMEPAGE_URL "https://"
        LANGUAGES CXX C
)

#add_compile_options(-Wundef -Wcast-align -Wchar-subscripts -Wnon-virtual-dtor -Wunused-local-typedefs -Wpointer-arith
#        -Wwrite-strings -Wformat-security -Wlogical-op -Wenum-conversion -Wdouble-promotion -Wconversion -Wshadow
#        -Wno-psabi -Wno-variadic-macros -Wno-long-long -fno-check-new -fno-common -fstrict-aliasing)

#Make sure that custom modules are found
list(INSERT CMAKE_MODULE_PATH 0 ${CMAKE_SOURCE_DIR}/cmake)

# Only do these if this is the main project, and not if it is included through add_subdirectory
if(PROJECT_IS_TOP_LEVEL)
  set(CMAKE_CXX_STANDARD 17)
  set(CMAKE_CXX_STANDARD_REQUIRED TRUE)

  # Ensure -std=c++xx instead of -std=g++xx
  set(CMAKE_CXX_EXTENSIONS OFF)

  set_property(GLOBAL PROPERTY USE_FOLDERS ON)

  # Testing only available if this is the main app
  # Note this needs to be done in the main CMakeLists
  # since it calls enable_testing, which must be in the
  # main CMakeLists.
  include(CTest)

  # Docs only available if this is the main app
  find_package(Doxygen)
  if(Doxygen_FOUND)
    add_subdirectory(docs)
  else()
    message(STATUS "Doxygen not found, not building docs")
  endif()
endif()

##############################################
# Add subdirectories
add_subdirectory(src)

# The executable code is here
#add_subdirectory(apps)

# Testing only available if this is the main app
# Emergency override TURINGFORGE_CMAKE_BUILD_TESTING provided as well
if ((PROJECT_IS_TOP_LEVEL OR TURINGFORGE_CMAKE_BUILD_TESTING) AND BUILD_TESTING)
  enable_testing()
  add_subdirectory(tests)
endif()

---

And additionally the `CMake` file responsible for building the library inside `src/`:

Code:

---

##############################################
# Find/Install system dependencies
include(FetchContent)
include(ExternalProject)

# Formatting library
FetchContent_Declare(
        fmtlib
        GIT_REPOSITORY https://github.com/fmtlib/fmt.git
        GIT_TAG 10.1.1)
set(FMT_INSTALL ON)
# Adds fmt::fmt
FetchContent_MakeAvailable(fmtlib)

# Eigen
FetchContent_Declare(
        Eigen
        GIT_REPOSITORY https://gitlab.com/libeigen/eigen.git
        GIT_TAG 3.4.0
        GIT_SHALLOW TRUE
        GIT_PROGRESS TRUE)
set(EIGEN_BUILD_DOC OFF)
set(BUILD_TESTING OFF)
set(EIGEN_BUILD_PKGCONFIG OFF)
set(CMAKE_POLICY_DEFAULT_CMP0077 NEW)
FetchContent_MakeAvailable(Eigen)

find_package (Eigen3 3.4 REQUIRED NO_MODULE)

# Fast float
FetchContent_Declare(
        fast_float
        GIT_REPOSITORY https://github.com/fastfloat/fast_float.git
        GIT_TAG tags/v6.0.0
        GIT_SHALLOW TRUE)
set(FASTFLOAT_INSTALL OFF)
# Adds fast_float
FetchContent_MakeAvailable(fast_float)

# Fast unordered map and set
FetchContent_Declare(
        unordered_dense
        GIT_REPOSITORY https://github.com/martinus/unordered_dense.git
        GIT_TAG tags/v4.3.1
        GIT_SHALLOW TRUE)
# Adds unordered_dense::unordered_dense
FetchContent_MakeAvailable(unordered_dense)

# SIMD vector operations
# TODO: Figure out how to install vectorclass using `FetchContent`
FetchContent_Declare(
        vectorclass
        GIT_REPOSITORY https://github.com/vectorclass/version2.git
        GIT_TAG tags/v2.02.01
        GIT_SHALLOW TRUE)
FetchContent_MakeAvailable(vectorclass)

# Fast hash functions
FetchContent_Declare(
        xxhash
        GIT_REPOSITORY https://github.com/Cyan4973/xxHash.git
        GIT_TAG tags/v0.8.2
        GIT_SHALLOW TRUE)
set(XXHASH_BUNDLED_MODE ON)
set(XXH_INLINE_ALL ON)
# Adds xxhash
FetchContent_MakeAvailable(xxHash)
file(GLOB XXHASH_SOURCES ${xxhash_SOURCE_DIR}/*.c)
list(REMOVE_ITEM XXHASH_SOURCES ${xxhash_SOURCE_DIR}/xxhsum.c)
list(REMOVE_ITEM XXHASH_SOURCES ${xxhash_SOURCE_DIR}/xxh_x86dispatch.c)
add_library(xxhash STATIC ${XXHASH_SOURCES})
target_include_directories(xxhash PUBLIC ${xxhash_SOURCE_DIR})

##############################################
# Create target and set properties

file(GLOB_RECURSE HEADER_LIST CONFIGURE_DEPENDS
        "${PROJECT_SOURCE_DIR}/include/turing_forge/*/*.hpp"
        "${PROJECT_SOURCE_DIR}/include/vstat/*.hpp"
        "${PROJECT_SOURCE_DIR}/include/csv/*.hpp"
)

file(GLOB SRC_LIST CONFIGURE_DEPENDS
        "${PROJECT_SOURCE_DIR}/src/*/*.cpp"
)

add_library(turingforge
        ${SRC_LIST}
        ${HEADER_LIST}
)

#Add an alias so that library can be used inside the build tree, e.g. when testing
add_library(Turingforge::turingforge ALIAS turingforge)

#Set target properties
target_include_directories(turingforge
        PUBLIC
            $<INSTALL_INTERFACE:include>
            $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
        PRIVATE
            ${CMAKE_CURRENT_SOURCE_DIR}/include/csv
            ${CMAKE_CURRENT_SOURCE_DIR}/include/vstat
)

target_compile_features(turingforge PRIVATE cxx_auto_type)
target_compile_options(turingforge PRIVATE
        $<$<OR:$<CXX_COMPILER_ID:Clang>,$<CXX_COMPILER_ID:AppleClang>,$<CXX_COMPILER_ID:GNU>>:-Wall -Wextra -pedantic -Werror>)

target_link_libraries(turingforge
        PUBLIC
            fmt::fmt Eigen3::Eigen unordered_dense::unordered_dense
        PRIVATE
            xxhash vectorclass fast_float
)

##############################################
# Installation instructions

option(TURINGFORGE_INSTALL "Enable install" ON)

if (TURINGFORGE_INSTALL)
    include(GNUInstallDirs)
    set(INSTALL_CONFIGDIR ${CMAKE_INSTALL_LIBDIR}/cmake/Turingforge)

    install(TARGETS turingforge
            EXPORT turingforge-targets
            LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
            ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
    )

    # This is required so that the exported target has the name Turingforge and not turingforge
    set_target_properties(turingforge PROPERTIES EXPORT_NAME Turingforge)

    install(DIRECTORY include/ DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})

    # Export the targets to a script
    install(EXPORT turingforge-targets
            FILE
                TuringforgeTargets.cmake
            NAMESPACE
                Turingforge::
            DESTINATION
                ${INSTALL_CONFIGDIR}
    )

    # Create a ConfigVersion.cmake file
    include(CMakePackageConfigHelpers)
    write_basic_package_version_file(
            ${CMAKE_CURRENT_BINARY_DIR}/TuringforgeConfigVersion.cmake
            VERSION ${PROJECT_VERSION}
            COMPATIBILITY AnyNewerVersion
    )

    configure_package_config_file(${CMAKE_CURRENT_LIST_DIR}/../cmake/TuringforgeConfig.cmake.in
            ${CMAKE_CURRENT_BINARY_DIR}/TuringforgeConfig.cmake
            INSTALL_DESTINATION ${INSTALL_CONFIGDIR}
    )

    # Install the config, configversion and custom find modules if any
    install(FILES
            ${CMAKE_CURRENT_BINARY_DIR}/TuringforgeConfig.cmake
            ${CMAKE_CURRENT_BINARY_DIR}/TuringforgeConfigVersion.cmake
            DESTINATION ${INSTALL_CONFIGDIR}
    )

    ##############################################
    ## Exporting from the build tree
    #configure_file(${CMAKE_CURRENT_LIST_DIR}/cmake/SOMECUSTOM.cmake
    #        ${CMAKE_CURRENT_BINARY_DIR}/SOMECUSTOM.cmake
    #        COPYONLY)

    export(EXPORT turingforge-targets
            FILE ${CMAKE_CURRENT_BINARY_DIR}/TuringforgeTargets.cmake
            NAMESPACE Turingforge::)

    # Register package in the User Package Registry
    export(PACKAGE Turingforge)

    # Make sure IDEs put the headers in a nice place
    source_group(
            TREE "${PROJECT_SOURCE_DIR}/include"
            PREFIX "Header Files"
            FILES ${HEADER_LIST}
    )
endif()

---

But it's not working that well for me due to a number of reasons. First of all I get these errors from `cmake`:

Code:

---

CMake Error: install(EXPORT "turingforge-targets" ...) includes target "turingforge" which requires target "unordered_dense" that is not in any export set.
CMake Error: install(EXPORT "turingforge-targets" ...) includes target "turingforge" which requires target "xxhash" that is not in any export set.
CMake Error: install(EXPORT "turingforge-targets" ...) includes target "turingforge" which requires target "fast_float" that is not in any export set.
CMake Error in src/CMakeLists.txt:
  export called with target "turingforge" which requires target
  "unordered_dense" that is not in any export set.


CMake Error in src/CMakeLists.txt:
  export called with target "turingforge" which requires target "xxhash" that
  is not in any export set.


CMake Error in src/CMakeLists.txt:
  export called with target "turingforge" which requires target "fast_float"
  that is not in any export set.

---

I have no idea what to do about `unordered_dense` since its own `CMake` files have no option about EXPORTING/INSTALLING, but for `fast_float` and `xxhash` I did set the relevant variables as seen in the code above. They make zero difference though and the errors still persist.

Apart from that, I am not sure how to using something like `FetchContent` to pull a codebase that has no `CMake` support like `vectorclass`.

Lastly, after getting away with my old simpler `CMake` file in favour of this one, I can't include anything in my source files. Even things like

Code:

---

#include <cstddef>

---

complain that the "file was not found", but also including things from my own header files with `myproject/core/somefile.hpp` that used to work, not does not any longer.

That's a lot of errors in one single file, but any hints are appreciated.