[Buildroot] [PATCH] core/pkg-cmake: better way to ass our CMAKE_MODULE_PATH

[Yann E. MORIN <yann.morin.1998@free.fr>]

All,

Woops, really bad typo in title... Will fix...

Regards,
Yann E. MORIN.

On 2017-03-04 18:24 +0100, Yann E. MORIN spake thusly:
> Currently, we tell cmake where to look for our own custom platform
> description by passing the path to the moduls directory on the command
> line.
> 
> However, this causes two different problems.
> 
> First, some packages simply set CMAKE_MODULE_PATH in their
> CMakeList.txt, thus overriding our own path, and then our platform
> description is not found.
> 
> Second, cmake may internally call sub-cmake (e.g. in the try_compile
> macro), but the CMAKE_MODULE_PATH is not automatically passed down in
> this case.
> 
> For the first problem, we could hunt down and fix all offenders, but
> this is an endless endeavour, especially since packagers are told to do
> so on the cmake wiki [0]:
> 
>     CMAKE_MODULE_PATH
>         tell CMake to search first in directories listed in
>         CMAKE_MODULE_PATH when you use FIND_PACKAGE() or INCLUDE()
>         SET(CMAKE_MODULE_PATH ${PROJECT_SOURCE_DIR}/MyCMakeScripts)
>         FIND_PACKAGE(HelloWorld)
> 
> The second problem could be solved by passing yet another variable on
> the command line, that tells cmake to explicitly pass arbitrary
> variables down to sub-cmake calls:
> 
>     -DCMAKE_TRY_COMPILE_PLATFORM_VARIABLES=CMAKE_MODULE_PATH
> 
> However, this only covers the case of try_compile. Even though no other
> case is known yet, we'd still risk missing locations where we would need
> to propagate CMAKE_MODULE_PATH, even some where we'd have no solution
> like for try_compile.
> 
> Instead, ngladitz on IRC suggested that CMAKE_MODULE_PATH be set
> directly from the toolchain file.
> 
> And indeed this fixes both problems explained above.
> 
> So be it.
> 
> [0] https://cmake.org/Wiki/CMake_Useful_Variables
> 
> Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
> Cc: Samuel Martin <s.martin49@gmail.com>
> Cc: J?rg Krause <joerg.krause@embedded.rocks>
> Cc: Ben Boeckel <mathstuf@gmail.com>
> Cc: Baruch Siach <baruch@tkos.co.il>
> Cc: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
> Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
> Cc: Arnout Vandecappelle <arnout@mind.be>
> Cc: Peter Korsgaard <peter@korsgaard.com>
> ---
>  package/pkg-cmake.mk                | 1 -
>  support/misc/toolchainfile.cmake.in | 4 ++++
>  2 files changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/package/pkg-cmake.mk b/package/pkg-cmake.mk
> index 77fa1dc..5d0a455 100644
> --- a/package/pkg-cmake.mk
> +++ b/package/pkg-cmake.mk
> @@ -87,7 +87,6 @@ define $(2)_CONFIGURE_CMDS
>  	PATH=$$(BR_PATH) \
>  	$$($$(PKG)_CONF_ENV) $$(BR2_CMAKE) $$($$(PKG)_SRCDIR) \
>  		-DCMAKE_TOOLCHAIN_FILE="$$(HOST_DIR)/usr/share/buildroot/toolchainfile.cmake" \
> -		-DCMAKE_MODULE_PATH="$$(HOST_DIR)/usr/share/buildroot" \
>  		-DCMAKE_INSTALL_PREFIX="/usr" \
>  		-DCMAKE_COLOR_MAKEFILE=OFF \
>  		-DBUILD_DOC=OFF \
> diff --git a/support/misc/toolchainfile.cmake.in b/support/misc/toolchainfile.cmake.in
> index 5a42644..c38800e 100644
> --- a/support/misc/toolchainfile.cmake.in
> +++ b/support/misc/toolchainfile.cmake.in
> @@ -10,6 +10,10 @@
>  # RELOCATED_HOST_DIR variable.
>  string(REPLACE "/usr/share/buildroot" "" RELOCATED_HOST_DIR ${CMAKE_CURRENT_LIST_DIR})
>  
> +# Point cmake to the location where we have our custom modules,
> +# so that it can find our custom platform description.
> +list(APPEND CMAKE_MODULE_PATH ${CMAKE_CURRENT_LIST_DIR})
> +
>  set(CMAKE_SYSTEM_NAME Buildroot)
>  set(CMAKE_SYSTEM_PROCESSOR @@CMAKE_SYSTEM_PROCESSOR@@)
>  
> -- 
> 2.7.4
> 

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