zephyr/cmake/compiler/gcc/target.cmake
Torsten Rasmussen 2e3873adde cmake: improve Zephyr link phase
Zephyr is a bare metal build where standard libs are disabled.

This means that c and runtime libraries must manually be linked in.

This has generally been handled by using CMake's link libraries handling
but the issue with that is both de-duplication but also library link
order.

Standard libraries must be linked at last location to ensure symbols
are always available, however this is not optimal with
target_link_libraries() because this would ultimately require every
library to know the c library to link with, which is not desired.

Therefore, setup standard C and runtime library linking in linker
CMake files for toolchains where this is required.

This commit expands the principle introduced with toolchain abstraction,
see PR#24851.

This means that a toolchain implementation may specify standard C,
runtime, C++, etc libraries, as well as their link order.
Because a property approach is used, then Zephyr modules, such as the
Picolibc module can adjust such properties.

An optional `zephyr_linker_finalize()` macro is called at the end of
Zephyr's CMakeList process and can be used by the toolchain
implementation to define the final linker invocation.

This aligns the linker handling flow to the principle introduced in
PR#24851 and improves the flexibility and robustness of Zephyr build
system.

Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>
2024-10-04 16:34:35 +01:00

139 lines
4.6 KiB
CMake

# SPDX-License-Identifier: Apache-2.0
set_ifndef(C++ g++)
# Configures CMake for using GCC, this script is re-used by several
# GCC-based toolchains
find_package(Deprecated COMPONENTS SPARSE)
find_program(CMAKE_C_COMPILER ${CROSS_COMPILE}${CC} PATHS ${TOOLCHAIN_HOME} NO_DEFAULT_PATH)
if(${CMAKE_C_COMPILER} STREQUAL CMAKE_C_COMPILER-NOTFOUND)
message(FATAL_ERROR "C compiler ${CROSS_COMPILE}${CC} not found - Please check your toolchain installation")
endif()
if(CONFIG_CPP)
set(cplusplus_compiler ${CROSS_COMPILE}${C++})
else()
if(EXISTS ${CROSS_COMPILE}${C++})
set(cplusplus_compiler ${CROSS_COMPILE}${C++})
else()
# When the toolchain doesn't support C++, and we aren't building
# with C++ support just set it to something so CMake doesn't
# crash, it won't actually be called
set(cplusplus_compiler ${CMAKE_C_COMPILER})
endif()
endif()
find_program(CMAKE_CXX_COMPILER ${cplusplus_compiler} PATHS ${TOOLCHAIN_HOME} NO_DEFAULT_PATH)
set(NOSTDINC "")
# Note that NOSYSDEF_CFLAG may be an empty string, and
# set_ifndef() does not work with empty string.
if(NOT DEFINED NOSYSDEF_CFLAG)
set(NOSYSDEF_CFLAG -undef)
endif()
# GCC-13, does not install limits.h on include-fixed anymore
# https://gcc.gnu.org/git/gitweb.cgi?p=gcc.git;h=be9dd80f933480
# Add check for GCC version >= 13.1
execute_process(
COMMAND ${CMAKE_C_COMPILER} -dumpfullversion
OUTPUT_VARIABLE temp_compiler_version
)
if("${temp_compiler_version}" VERSION_GREATER_EQUAL 13.1.0)
set(fix_header_file include/limits.h)
else()
set(fix_header_file include-fixed/limits.h)
endif()
foreach(file_name include/stddef.h "${fix_header_file}")
execute_process(
COMMAND ${CMAKE_C_COMPILER} --print-file-name=${file_name}
OUTPUT_VARIABLE _OUTPUT
)
get_filename_component(_OUTPUT "${_OUTPUT}" DIRECTORY)
string(REGEX REPLACE "\n" "" _OUTPUT "${_OUTPUT}")
list(APPEND NOSTDINC ${_OUTPUT})
endforeach()
include(${ZEPHYR_BASE}/cmake/gcc-m-cpu.cmake)
include(${ZEPHYR_BASE}/cmake/gcc-m-fpu.cmake)
if("${ARCH}" STREQUAL "arm")
include(${ZEPHYR_BASE}/cmake/compiler/gcc/target_arm.cmake)
elseif("${ARCH}" STREQUAL "arm64")
include(${ZEPHYR_BASE}/cmake/compiler/gcc/target_arm64.cmake)
elseif("${ARCH}" STREQUAL "arc")
include(${ZEPHYR_BASE}/cmake/compiler/gcc/target_arc.cmake)
elseif("${ARCH}" STREQUAL "riscv")
include(${CMAKE_CURRENT_LIST_DIR}/target_riscv.cmake)
elseif("${ARCH}" STREQUAL "x86")
include(${CMAKE_CURRENT_LIST_DIR}/target_x86.cmake)
elseif("${ARCH}" STREQUAL "sparc")
include(${CMAKE_CURRENT_LIST_DIR}/target_sparc.cmake)
elseif("${ARCH}" STREQUAL "mips")
include(${CMAKE_CURRENT_LIST_DIR}/target_mips.cmake)
elseif("${ARCH}" STREQUAL "xtensa")
include(${CMAKE_CURRENT_LIST_DIR}/target_xtensa.cmake)
endif()
if(SYSROOT_DIR)
# The toolchain has specified a sysroot dir, pass it to the compiler
list(APPEND TOOLCHAIN_C_FLAGS
--sysroot=${SYSROOT_DIR}
)
# Use sysroot dir to set the libc path's
execute_process(
COMMAND ${CMAKE_C_COMPILER} ${TOOLCHAIN_C_FLAGS} --print-multi-directory
OUTPUT_VARIABLE NEWLIB_DIR
OUTPUT_STRIP_TRAILING_WHITESPACE
)
set(LIBC_LIBRARY_DIR "\"${SYSROOT_DIR}\"/lib/${NEWLIB_DIR}")
endif()
# This libgcc code is partially duplicated in compiler/*/target.cmake
execute_process(
COMMAND ${CMAKE_C_COMPILER} ${TOOLCHAIN_C_FLAGS} --print-libgcc-file-name
OUTPUT_VARIABLE LIBGCC_FILE_NAME
OUTPUT_STRIP_TRAILING_WHITESPACE
)
assert_exists(LIBGCC_FILE_NAME)
get_filename_component(LIBGCC_DIR ${LIBGCC_FILE_NAME} DIRECTORY)
assert_exists(LIBGCC_DIR)
set_linker_property(PROPERTY lib_include_dir "-L\"${LIBGCC_DIR}\"")
# For CMake to be able to test if a compiler flag is supported by the
# toolchain we need to give CMake the necessary flags to compile and
# link a dummy C file.
#
# CMake checks compiler flags with check_c_compiler_flag() (Which we
# wrap with target_cc_option() in extensions.cmake)
foreach(isystem_include_dir ${NOSTDINC})
list(APPEND isystem_include_flags -isystem "\"${isystem_include_dir}\"")
endforeach()
# The CMAKE_REQUIRED_FLAGS variable is used by check_c_compiler_flag()
# (and other commands which end up calling check_c_source_compiles())
# to add additional compiler flags used during checking. These flags
# are unused during "real" builds of Zephyr source files linked into
# the final executable.
#
# Appending onto any existing values lets users specify
# toolchain-specific flags at generation time.
list(APPEND CMAKE_REQUIRED_FLAGS
-nostartfiles
-nostdlib
${isystem_include_flags}
-Wl,--unresolved-symbols=ignore-in-object-files
-Wl,--entry=0 # Set an entry point to avoid a warning
)
string(REPLACE ";" " " CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS}")