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In36568732e4, we expanded toolchain.cmake to also define the value for CMAKE_SYSTEM_VERSION, as the cmake documentation states that it must be manually defined when doing cross-compilation [0]: When the CMAKE_SYSTEM_NAME variable is set explicitly to enable cross compiling then the value of CMAKE_SYSTEM_VERSION must also be set explicitly to specify the target system version. However, the fix in36568732e4uses the version of the kernel headers, assuming that would be the oldest kernel we could run on. Yet, this is not the case, because glibc (for example) has fallbacks to support running on kernels older than the headers it was built against. The cmake official wiki [1] additionally states: * CMAKE_SYSTEM_VERSION : optional, version of your target system, not used very much. Folllowed a little bit below, by: * CMAKE_TOOLCHAIN_FILE : absolute or relative path to a cmake script which sets up all the toolchain related variables mentioned above For instance for crosscompiling from Linux to Embedded Linux on PowerPC this file could look like this: # this one is important SET(CMAKE_SYSTEM_NAME Linux) #this one not so much SET(CMAKE_SYSTEM_VERSION 1) [...] Furthermore, using the kernel headers version can be a bit misleading (as it really looks like is is the correct version to use when it is not), while it is obvious that 1 is not really the output of `uname -r` and thus is definitely not misleading. Finally, random searches [2] about CMAKE_SYSTEM_VERSION, mostly only turns up issues related with Windows, Mac-OS, and to a lesser extent, Android (where it is forcibly set to 1), with issues realted to running under just Linux (as opposed to Adnroid) mostly non-existent. Consequently, we revert to using the value that is suggested in the cmake WiKi, i.e. 1, and which is basically what we also used as a workaround in the azure-iot-sdk-c paclkage up untild300b1d3b1. A case were we will need to have a real kernel version, is if we one day have a cmake-based pacakge that builds and installs a kernel module [3], because it will need the _running_ kernel version to install it in /lib/modules/VERSION/, but in that case it will anyway most probably not be the headers version. [0] https://cmake.org/cmake/help/v3.8/variable/CMAKE_SYSTEM_VERSION.html [1] https://gitlab.kitware.com/cmake/community/wikis/doc/cmake/CrossCompiling [2] https://duckduckgo.com/?q=CMAKE_SYSTEM_VERSION [3] https://stackoverflow.com/questions/38205745/cmake-system-version-not-updated-for-new-kernel Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr> Cc: Arnout Vandecappelle <arnout@mind.be> Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com> Cc: Samuel Martin <s.martin49@gmail.com> Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be> Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
72 lines
3.4 KiB
CMake
72 lines
3.4 KiB
CMake
#
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# Automatically generated file; DO NOT EDIT.
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# CMake toolchain file for Buildroot
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#
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# In order to allow the toolchain to be relocated, we calculate the
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# HOST_DIR based on this file's location: $(HOST_DIR)/share/buildroot
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# and store it in RELOCATED_HOST_DIR.
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# All the other variables that need to refer to HOST_DIR will use the
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# RELOCATED_HOST_DIR variable.
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string(REPLACE "/share/buildroot" "" RELOCATED_HOST_DIR ${CMAKE_CURRENT_LIST_DIR})
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# Point cmake to the location where we have our custom modules,
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# so that it can find our custom platform description.
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list(APPEND CMAKE_MODULE_PATH ${CMAKE_CURRENT_LIST_DIR})
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set(CMAKE_SYSTEM_NAME Buildroot)
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set(CMAKE_SYSTEM_VERSION 1)
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set(CMAKE_SYSTEM_PROCESSOR @@CMAKE_SYSTEM_PROCESSOR@@)
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# Set the {C,CXX}FLAGS appended by CMake depending on the build type
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# defined by Buildroot. CMake defaults these variables with -g and/or
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# -O options, and they are appended at the end of the argument list,
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# so the Buildroot options are overridden. Therefore these variables
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# have to be cleared, so that the options passed in CMAKE_C_FLAGS do
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# apply.
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#
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# Note:
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# if the project forces some of these flag variables, Buildroot is
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# screwed up and there is nothing Buildroot can do about that :(
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set(CMAKE_C_FLAGS_DEBUG "" CACHE STRING "Debug CFLAGS")
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set(CMAKE_CXX_FLAGS_DEBUG "" CACHE STRING "Debug CXXFLAGS")
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set(CMAKE_C_FLAGS_RELEASE " -DNDEBUG" CACHE STRING "Release CFLAGS")
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set(CMAKE_CXX_FLAGS_RELEASE " -DNDEBUG" CACHE STRING "Release CXXFLAGS")
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# Build type from the Buildroot configuration
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set(CMAKE_BUILD_TYPE @@CMAKE_BUILD_TYPE@@ CACHE STRING "Buildroot build configuration")
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# Buildroot defaults flags.
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# If you are using this toolchainfile.cmake file outside of Buildroot and
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# want to customize the compiler/linker flags, then:
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# * set them all on the cmake command line, e.g.:
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# cmake -DCMAKE_C_FLAGS="@@TARGET_CFLAGS@@ -Dsome_custom_flag" ...
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# * and make sure the project's CMake code extends them like this if needed:
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# set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Dsome_definitions")
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set(CMAKE_C_FLAGS "@@TARGET_CFLAGS@@" CACHE STRING "Buildroot CFLAGS")
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set(CMAKE_CXX_FLAGS "@@TARGET_CXXFLAGS@@" CACHE STRING "Buildroot CXXFLAGS")
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set(CMAKE_EXE_LINKER_FLAGS "@@TARGET_LDFLAGS@@" CACHE STRING "Buildroot LDFLAGS for executables")
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set(CMAKE_SHARED_LINKER_FLAGS "@@TARGET_LDFLAGS@@" CACHE STRING "Buildroot LDFLAGS for shared libraries")
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set(CMAKE_MODULE_LINKER_FLAGS "@@TARGET_LDFLAGS@@" CACHE STRING "Buildroot LDFLAGS for module libraries")
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set(CMAKE_INSTALL_SO_NO_EXE 0)
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set(CMAKE_PROGRAM_PATH "${RELOCATED_HOST_DIR}/bin")
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set(CMAKE_SYSROOT "${RELOCATED_HOST_DIR}/@@STAGING_SUBDIR@@")
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set(CMAKE_FIND_ROOT_PATH "${RELOCATED_HOST_DIR}/@@STAGING_SUBDIR@@")
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set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
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set(CMAKE_FIND_ROOT_PATH_MODE_PACKAGE ONLY)
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set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
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set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
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set(ENV{PKG_CONFIG_SYSROOT_DIR} "${RELOCATED_HOST_DIR}/@@STAGING_SUBDIR@@")
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# This toolchain file can be used both inside and outside Buildroot.
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set(CMAKE_C_COMPILER "${RELOCATED_HOST_DIR}/@@TARGET_CC@@")
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set(CMAKE_CXX_COMPILER "${RELOCATED_HOST_DIR}/@@TARGET_CXX@@")
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if(@@TOOLCHAIN_HAS_FORTRAN@@)
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set(CMAKE_Fortran_FLAGS_DEBUG "" CACHE STRING "Debug Fortran FLAGS")
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set(CMAKE_Fortran_FLAGS_RELEASE " -DNDEBUG" CACHE STRING "Release Fortran FLAGS")
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set(CMAKE_Fortran_FLAGS "@@TARGET_FCFLAGS@@" CACHE STRING "Buildroot FCFLAGS")
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set(CMAKE_Fortran_COMPILER "${RELOCATED_HOST_DIR}/@@TARGET_FC@@")
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endif()
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