[v6,9/9] toochainfile.cmake: rework the way Buildroot sets flags

From the build configuration, Buildroot defines and set some compiler
and linker flags that should be passed to any packages build-system.

For package using the cmake-package infrastructure, this is achieved
via the toolchainfile.cmake.

This change simplifies the way the toolchainfile.cmake file handles
these flags: it now just sets them, without any attempt to extend them
with those Buildroot defined.

This change still allows overriding these flags from the configure
command line.

So, now, when a CMake-based package needs to extend them, they should
be fully set from the package *.mk file. This behavior is consistent
with what is done for others package infrastructures.

This change should not pull any regression WRT the bug #7280 [1].

However, now, when someone uses the toolchainfile.cmake file outside of
Buildroot, he/she must overload all compiler/linker flags (including the
ones Buildroot sets since they no longer get automatically added).

[1] https://bugs.busybox.net/show_bug.cgi?id=7280

Cc: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Samuel Martin <s.martin49@gmail.com>

---
changes v5->v6:
- none

changes v4->v5:
- fix cmake set call

changes v3->v4:
- add a note about what the CMake code should look like (Arnout)
- fix overriding support (add missing CACHE keyword)
- update CHANGES text
---
 CHANGES                             |  5 ++++-
 support/misc/toolchainfile.cmake.in | 17 +++++++++++++----
 2 files changed, 17 insertions(+), 5 deletions(-)

On 16-10-16 13:12, Samuel Martin wrote:
>>From the build configuration, Buildroot defines and set some compiler
                                                         ^s

> and linker flags that should be passed to any packages build-system.
> 
> For package using the cmake-package infrastructure, this is achieved
             ^s

> via the toolchainfile.cmake.
> 
> This change simplifies the way the toolchainfile.cmake file handles
> these flags: it now just sets them, without any attempt to extend them
> with those Buildroot defined.
> 
> This change still allows overriding these flags from the configure
> command line.
> 
> So, now, when a CMake-based package needs to extend them, they should
> be fully set from the package *.mk file. This behavior is consistent
> with what is done for others package infrastructures.
> 
> This change should not pull any regression WRT the bug #7280 [1].
> 
> However, now, when someone uses the toolchainfile.cmake file outside of
> Buildroot, he/she must overload all compiler/linker flags (including the
> ones Buildroot sets since they no longer get automatically added).
> 
> [1] https://bugs.busybox.net/show_bug.cgi?id=7280
> 
> Cc: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
> Cc: Max Filippov <jcmvbkbc@gmail.com>
> Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
> Signed-off-by: Samuel Martin <s.martin49@gmail.com>

Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

> 
> ---
> changes v5->v6:
> - none
> 
> changes v4->v5:
> - fix cmake set call
> 
> changes v3->v4:
> - add a note about what the CMake code should look like (Arnout)
> - fix overriding support (add missing CACHE keyword)
> - update CHANGES text
> ---
>  CHANGES                             |  5 ++++-
>  support/misc/toolchainfile.cmake.in | 17 +++++++++++++----
>  2 files changed, 17 insertions(+), 5 deletions(-)
> 
> diff --git a/CHANGES b/CHANGES
> index c0e3e79..3657710 100644
> --- a/CHANGES
> +++ b/CHANGES
> @@ -2,7 +2,10 @@
>  
>      toolchainfile.cmake:
>      * when used outside of Buildroot, if not specified on the command
> -      line, the CMAKE_BUILD_TYPE is by toolchainfile.cmake.
> +      line, the CMAKE_BUILD_TYPE is by toolchainfile.cmake;

 Don't forget to amend this with the missing "set"


 Regards,
 Arnout


> +    * when used outside of Buildroot with custom compiler/linker
> +      flags, the Buildroot flags should be set along side with the
> +      custom ones.
>  
>  2016.08, Released September 1st, 2016
>  
> diff --git a/support/misc/toolchainfile.cmake.in b/support/misc/toolchainfile.cmake.in
> index 2ace940..0283b62 100644
> --- a/support/misc/toolchainfile.cmake.in
> +++ b/support/misc/toolchainfile.cmake.in
> @@ -27,9 +27,17 @@ set(CMAKE_CXX_FLAGS_RELEASE " -DNEBUG" CACHE STRING "Release CXXFLAGS")
>  # Build type from the Buildroot configuration
>  set(CMAKE_BUILD_TYPE @@CMAKE_BUILD_TYPE@@ CACHE STRING "Buildroot build configuration")
>  
> -set(CMAKE_C_FLAGS "@@TARGET_CFLAGS@@ ${CMAKE_C_FLAGS}" CACHE STRING "Buildroot CFLAGS")
> -set(CMAKE_CXX_FLAGS "@@TARGET_CXXFLAGS@@ ${CMAKE_CXX_FLAGS}" CACHE STRING "Buildroot CXXFLAGS")
> -set(CMAKE_EXE_LINKER_FLAGS "@@TARGET_LDFLAGS@@ ${CMAKE_EXE_LINKER_FLAGS}" CACHE STRING "Buildroot LDFLAGS")
> +# Buildroot defaults flags.
> +# If you are using this toolchainfile.cmake file outside of Buildroot and
> +# want to customize the compiler/linker flags, then:
> +# * set them all on the cmake command line, e.g.:
> +#     cmake -DCMAKE_C_FLAGS="@@TARGET_CFLAGS@@ -Dsome_custom_flag" ...
> +# * and make sure the project's CMake code extendsthem like this if needed:
> +#     set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Dsome_definitions")
> +set(CMAKE_C_FLAGS "@@TARGET_CFLAGS@@" CACHE STRING "Buildroot CFLAGS")
> +set(CMAKE_CXX_FLAGS "@@TARGET_CXXFLAGS@@" CACHE STRING "Buildroot CXXFLAGS")
> +set(CMAKE_EXE_LINKER_FLAGS "@@TARGET_LDFLAGS@@" CACHE STRING "Buildroot LDFLAGS for executables")
> +
>  set(CMAKE_INSTALL_SO_NO_EXE 0)
>  
>  set(CMAKE_PROGRAM_PATH "${RELOCATED_HOST_DIR}/usr/bin")
> @@ -45,6 +53,7 @@ set(ENV{PKG_CONFIG_SYSROOT_DIR} "${RELOCATED_HOST_DIR}/@@STAGING_SUBDIR@@")
>  set(CMAKE_C_COMPILER "${RELOCATED_HOST_DIR}/@@TARGET_CC@@")
>  set(CMAKE_CXX_COMPILER "${RELOCATED_HOST_DIR}/@@TARGET_CXX@@")
>  if(@@TOOLCHAIN_HAS_FORTRAN@@)
> -  set(CMAKE_Fortran_FLAGS "@@TARGET_FCFLAGS@@ ${CMAKE_Fortran_FLAGS}" CACHE STRING "Buildroot FCFLAGS")
> +  # Buildroot defaults flags.
> +  set(CMAKE_Fortran_FLAGS "@@TARGET_FCFLAGS@@" CACHE STRING "Buildroot FCFLAGS")
>    set(CMAKE_Fortran_COMPILER "${RELOCATED_HOST_DIR}/@@TARGET_FC@@")
>  endif()
>