OSDev.org

cmake_minimum_required(VERSION 3.16.3)

# Set the active output directories:
set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY build/x86_64/lib)
set(CMAKE_LIBRARY_OUTPUT_DIRECTORY build/x86_64/lib)
set(CMAKE_RUNTIME_OUTPUT_DIRECTORY build/x86_64/bin)

project(kernel)

set(PROJECT_VERSION_MAJOR 0)
set(PROJECT_VERSION_MINOR 1)

set(CMAKE_CXX_STANDAED 17)

set(KERNEL_BIN "x86_64-kernel.bin")

set(LINKER_SCRIPT targets/x86_64/linker.ld)
set(GRUB_CFG targets/x86_64/iso/boot/grub/grub.cfg)

set(CMAKE_ASM_NASM_OBJECT_FORMAT "elf64")

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -mno-red-zone -mcmodel=large -mno-sse -ffreestanding -nostdlib -fno-pie -fno-pic -no-pie")
set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -mno-red-zone -mcmodel=large -mno-sse -ffreestanding -nostdlib -fno-pie -fno-pic -no-pie")
set(CMAKE_ASM_FLAGS "{CMAKE_ASM_FLAGS} -felf64")

set(CMAKE_CXX_COMPILER "/usr/bin/gcc")
set(CMAKE_C_COMPILER "/usr/bin/g++")
set(CMAKE_LINKER "/usr/bin/ld")

enable_language(ASM_NASM)

file(GLOB KERNEL_C_MODULES src/impl/kernel/*.c)
file(GLOB X86_64_C_MODULES src/impl/x86_64/*.c)
file(GLOB BOOT_ASM_MODULES src/impl/x86_64/boot/*.asm)

add_executable(
    ${KERNEL_BIN}
    
    ${KERNEL_C_MODULES}
    ${X86_64_C_MODULES}
    ${BOOT_ASM_MODULES}
    )

set(CMAKE_LINKER "/usr/bin/ld")
set(CMAKE_LINKER_FLAGS "-n -o -T ${LINKER_SCRIPT}")
set(CMAKE_CXX_LINK_EXECUTABLE "<CMAKE_LINKER> ${CMAKE_LINKER_FLAGS} <OBJECTS> -o <TARGET> <LINK_LIBRARIES>")

include_directories(src/intf)
target_include_directories(${KERNEL_BIN} PUBLIC src/intf)

set_target_properties(${KERNEL_BIN} PROPERTIES LINK_FLAGS "-n -T ${LINKER_SCRIPT}")

add_custom_command(TARGET ${KERNEL_BIN} POST_BUILD
    COMMAND mkdir -p build/x86_64/boot/grub
    COMMAND cp ${KERNEL_BIN} build/x86_64/boot/${KERNEL_BIN}
    COMMAND cp ${GRUB_CFG} build/x86_64/boot/grub
    COMMAND grub-mkrescue -o kernel.iso build/x86_64/
    COMMAND rm -r build/
    )

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nullplan wrote:You are compiling with G++. That is because you are assigning CMAKE_C_COMPILER and CMAKE_CXX_COMPILER the wrong way round. g++ will compile all your files in C++ mode. However, C++ functions get name mangled. You could add 'extern "C"' to the declaration, but that would really only be treating the symptom. Get CMake to compile your C files with GCC. And get yourself a cross compiler! Using the host compiler is discouraged for a variety of reasons, not least of which being that libgcc depends on your host OS.

Solar wrote:

Code: Select all

cmake_minimum_required(VERSION 3.16.3)

My answer to Which CMake version as the minimum? would be relevant here. Pick your minimum_required for a good reason...

Code: Select all

set(CMAKE_CXX_STANDAED 17)

The typo aside, I don't see your setup actually using any C++, so why are you bothering with these settings in the first place? For a kernel, pick one language and stick to it. Mixing C and C++ in kernel space seems quite ill-advised. Despite their common heritage and quite large intersection of features, these to languages don't mix too well when you get to the fine print (as you are bound to do in kernel space).

Solar wrote:The typo aside, I don't see your setup actually using any C++, so why are you bothering with these settings in the first place? For a kernel, pick one language and stick to it. Mixing C and C++ in kernel space seems quite ill-advised. Despite their common heritage and quite large intersection of features, these to languages don't mix too well when you get to the fine print (as you are bound to do in kernel space).