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Since commit [1] (core/pkg-cmake: provide our own platform
description), Buildroot is setting its own CMake platform
description. This description applies minor changes on top of
the CMake Linux platform, see [2] and [3]. The CMake system specific
script tries to include an initialization script, if present.
See [4].
Since in commit [1] we set the CMAKE_SYSTEM_NAME to "Buildroot"
(rather than "Linux"), CMake will search for a
"Platform/Buildroot-Initialize.cmake" which does not exist, and
continue normally, since the include is optional.
The "Platform/Linux-Initialize.cmake" file is the one setting the
LINUX [6] and UNIX [7] variables, which are expected to be true on
a linux compatible system. In Buildroot, it is currently not
included, so those variables are unset.
If a CMake package in Buildroot has a construct such as:
if(LINUX)
# ...do things...
else()
message(FATAL_ERROR "System not supported")
endif()
It will fail at configuration time.
This situation happened when trying to add the btop++ package
in Buildroot. See [8].
Since the initial intent of commit [1] was to make the Buildroot
CMake system inherit from Linux plus some fixups, this commit simply
adds a Buildroot-Initialize.cmake file that includes the
Linux-Initialize.cmake one from CMake. This will have the effect
to properly define the LINUX and UNIX variables.
[1] c69b14fe2f
[2] https://gitlab.com/buildroot.org/buildroot/-/blob/2025.11/support/misc/Buildroot.cmake#L1-4
[3] https://cmake.org/cmake/help/v4.2/variable/CMAKE_SYSTEM_NAME.html
[4] https://gitlab.kitware.com/cmake/cmake/-/blob/v4.2.1/Modules/CMakeSystemSpecificInitialize.cmake#L35
[5] https://gitlab.kitware.com/cmake/cmake/-/blob/v4.2.1/Modules/Platform/Linux-Initialize.cmake
[6] https://cmake.org/cmake/help/v4.2/variable/LINUX.html
[7] https://cmake.org/cmake/help/v4.2/variable/UNIX.html
[8] https://github.com/aristocratos/btop/blob/v1.4.6/CMakeLists.txt#L76
Reported-by: Gilles Talis <gilles.talis@gmail.com>
Signed-off-by: Julien Olivain <ju.o@free.fr>
Tested-by: Gilles Talis <gilles.talis@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Buildroot is a simple, efficient and easy-to-use tool to generate embedded Linux systems through cross-compilation. The documentation can be found in docs/manual. You can generate a text document with 'make manual-text' and read output/docs/manual/manual.text. Online documentation can be found at https://buildroot.org/docs.html To build and use the buildroot stuff, do the following: 1) run 'make menuconfig' 2) select the target architecture and the packages you wish to compile 3) run 'make' 4) wait while it compiles 5) find the kernel, bootloader, root filesystem, etc. in output/images You do not need to be root to build or run buildroot. Have fun! Buildroot comes with a basic configuration for a number of boards. Run 'make list-defconfigs' to view the list of provided configurations. Please feed suggestions, bug reports, insults, and bribes back to the buildroot mailing list: buildroot@buildroot.org You can also find us on #buildroot on OFTC IRC. If you would like to contribute patches, please read https://buildroot.org/manual.html#submitting-patches