[Buildroot] [PATCH 1/1] package/pkg-cmake.mk: add Platform/Buildroot-Initialize.cmake

[Buildroot] [PATCH 1/1] package/pkg-cmake.mk: add Platform/Buildroot-Initialize.cmake

[Julien Olivain via buildroot]

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] https://gitlab.com/buildroot.org/buildroot/-/commit/c69b14fe2f72d8134057b115884c04a2bf27d410
[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>
---
 package/pkg-cmake.mk                    | 2 ++
 support/misc/Buildroot-Initialize.cmake | 1 +
 2 files changed, 3 insertions(+)
 create mode 100644 support/misc/Buildroot-Initialize.cmake

diff --git a/package/pkg-cmake.mk b/package/pkg-cmake.mk
index ba287d244a..f572bdebb3 100644
--- a/package/pkg-cmake.mk
+++ b/package/pkg-cmake.mk
@@ -287,6 +287,8 @@ define TOOLCHAIN_CMAKE_INSTALL_FILES
 		> $(HOST_DIR)/share/buildroot/toolchainfile.cmake
 	$(Q)$(INSTALL) -D -m 0644 support/misc/Buildroot.cmake \
 		$(HOST_DIR)/share/buildroot/Platform/Buildroot.cmake
+	$(Q)$(INSTALL) -D -m 0644 support/misc/Buildroot-Initialize.cmake \
+		$(HOST_DIR)/share/buildroot/Platform/Buildroot-Initialize.cmake
 endef
 
 TOOLCHAIN_POST_INSTALL_STAGING_HOOKS += TOOLCHAIN_CMAKE_INSTALL_FILES
diff --git a/support/misc/Buildroot-Initialize.cmake b/support/misc/Buildroot-Initialize.cmake
new file mode 100644
index 0000000000..3451562f08
--- /dev/null
+++ b/support/misc/Buildroot-Initialize.cmake
@@ -0,0 +1 @@
+include(Platform/Linux-Initialize)
-- 
2.52.0

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Re: [Buildroot] [PATCH 1/1] package/pkg-cmake.mk: add Platform/Buildroot-Initialize.cmake

[Gilles Talis]

Hi Julien, all,

Le sam. 17 janv. 2026 à 06:32, Julien Olivain <ju.o@free.fr> a écrit :
>
> 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] https://gitlab.com/buildroot.org/buildroot/-/commit/c69b14fe2f72d8134057b115884c04a2bf27d410
> [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>
> ---
>  package/pkg-cmake.mk                    | 2 ++
>  support/misc/Buildroot-Initialize.cmake | 1 +
>  2 files changed, 3 insertions(+)
>  create mode 100644 support/misc/Buildroot-Initialize.cmake
>
> diff --git a/package/pkg-cmake.mk b/package/pkg-cmake.mk
> index ba287d244a..f572bdebb3 100644
> --- a/package/pkg-cmake.mk
> +++ b/package/pkg-cmake.mk
> @@ -287,6 +287,8 @@ define TOOLCHAIN_CMAKE_INSTALL_FILES
>                 > $(HOST_DIR)/share/buildroot/toolchainfile.cmake
>         $(Q)$(INSTALL) -D -m 0644 support/misc/Buildroot.cmake \
>                 $(HOST_DIR)/share/buildroot/Platform/Buildroot.cmake
> +       $(Q)$(INSTALL) -D -m 0644 support/misc/Buildroot-Initialize.cmake \
> +               $(HOST_DIR)/share/buildroot/Platform/Buildroot-Initialize.cmake
>  endef
>
>  TOOLCHAIN_POST_INSTALL_STAGING_HOOKS += TOOLCHAIN_CMAKE_INSTALL_FILES
> diff --git a/support/misc/Buildroot-Initialize.cmake b/support/misc/Buildroot-Initialize.cmake
> new file mode 100644
> index 0000000000..3451562f08
> --- /dev/null
> +++ b/support/misc/Buildroot-Initialize.cmake
> @@ -0,0 +1 @@
> +include(Platform/Linux-Initialize)
> --
> 2.52.0
>
Thanks for the patch.
I could successfully build btop++ after I applied it. So:

Tested-by: Gilles Talis <gilles.talis@gmail.com>
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Re: [Buildroot] [PATCH 1/1] package/pkg-cmake.mk: add Platform/Buildroot-Initialize.cmake

[Thomas Petazzoni via buildroot]

On Sat, Jan 17, 2026 at 11:31:09AM +0100, Julien Olivain via buildroot wrote:
> 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] https://gitlab.com/buildroot.org/buildroot/-/commit/c69b14fe2f72d8134057b115884c04a2bf27d410
> [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>

Applied, thanks!

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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