[Buildroot] [PATCH 05/14] pkg-cmake.mk: enable ccache for cmake packages

[Samuel Martin]

Arnout, all,

On Fri, Apr 25, 2014 at 12:39 AM, Arnout Vandecappelle <arnout at mind.be> wrote:
> On 24/04/14 00:48, Samuel Martin wrote:
>> This patch updates the generated toolchainfile.cmake to use ccache.
>>
>> When toolchainfile.cmake is used inside Buildroot, using ccache during
>> the build is driven by a CMake knob: USE_CCACHE, automatically set by
>> the cmake-package infrastructure and reflecting the BR2_CCACHE value.
>>
>> Since this toolchainefile.cmake file can be used outside Buildroot, and
>> this file also set a couple of things (among these: the sysroot cflag,
>> some pkg-config environment variables), it is important to set the
>> compiler variables as well to keep the consistency of the
>> cross-compilation configuration.
>> So, when it is used outside Buildroot, using ccache for the build is
>> driven by the ccache program availability.
>
>  I don't understand this. We can just use br-ccache when it's called from
> outside buildroot as well, no?

One may want to use ccache in Buildroot to build its rootfs, but not
when building its project.
Does this use-case make sense?

>
>
>>
>> Note that using ccache for the build is achieved by setting the *_ARG1/cc
>> CMake variables to let CMake use ccache without failing in detecting
>> the compiler.
>>
>> Signed-off-by: Samuel Martin <s.martin49 at gmail.com>
>> Signed-off-by: Luca Ceresoli <luca at lucaceresoli.net>
>> Cc: Luca Ceresoli <luca at lucaceresoli.net>
>>
>> ---
>> changes v2 -> v3 (Samuel):
>> - rebase
>> - inline the -DUSE_CCACHE=... in the configure commands.
>> - always set the compiler variables, even when called for outside
>>   Buildroot.
>> - update commit message
>>
>> changes v1 -> v2 (Luca):
>> - totally reimplemented based on Samuel's suggestion;
>> - added dependency on host-ccache for cmake packages if ccache is
>>   enabled.
>> ---
>>  package/pkg-cmake.mk | 35 +++++++++++++++++++++++++++++++++--
>>  1 file changed, 33 insertions(+), 2 deletions(-)
>>
>> diff --git a/package/pkg-cmake.mk b/package/pkg-cmake.mk
>> index b2ac2df..a032426 100644
>> --- a/package/pkg-cmake.mk
>> +++ b/package/pkg-cmake.mk
>> @@ -66,6 +66,7 @@ define $(2)_CONFIGURE_CMDS
>>               -DCMAKE_INSTALL_PREFIX="/usr" \
>>               -DCMAKE_COLOR_MAKEFILE=OFF \
>>               -DBUILD_SHARED_LIBS=$(if $(BR2_PREFER_STATIC_LIB),OFF,ON) \
>> +             -DUSE_CCACHE=$(if $(BR2_CCACHE),ON,OFF) \
>>               $$($$(PKG)_CONF_OPT) \
>>       )
>>  endef
>> @@ -83,6 +84,7 @@ define $(2)_CONFIGURE_CMDS
>>               -DCMAKE_FIND_ROOT_PATH_MODE_LIBRARY="BOTH" \
>>               -DCMAKE_FIND_ROOT_PATH_MODE_INCLUDE="BOTH" \
>>               -DCMAKE_INSTALL_PREFIX="$$(HOST_DIR)/usr" \
>> +             -DUSE_CCACHE=$(if $(BR2_CCACHE),ON,OFF) \
>>               $$($$(PKG)_CONF_OPT) \
>>       )
>>  endef
>> @@ -161,8 +163,6 @@ host-cmake-package = $(call inner-cmake-package,host-$(pkgname),$(call UPPERCASE
>>  define TOOLCHAINFILE_CMAKE
>>  string(REPLACE /usr/share/buildroot "" _HOST_DIR $${CMAKE_CURRENT_LIST_DIR})
>>  set(CMAKE_SYSTEM_NAME Linux)
>> -set(CMAKE_C_COMPILER $(subst $(HOST_DIR),$${_HOST_DIR},$(TARGET_CROSS))gcc)
>> -set(CMAKE_CXX_COMPILER $(subst $(HOST_DIR),$${_HOST_DIR},$(TARGET_CROSS))g++)
>>  set(CMAKE_C_FLAGS "$${CMAKE_C_FLAGS} $(TARGET_CFLAGS)" CACHE STRING "Buildroot CFLAGS" FORCE)
>>  set(CMAKE_CXX_FLAGS "$${CMAKE_CXX_FLAGS} $(TARGET_CXXFLAGS)" CACHE STRING "Buildroot CXXFLAGS" FORCE)
>>  set(CMAKE_INSTALL_SO_NO_EXE 0)
>> @@ -172,6 +172,37 @@ set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
>>  set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
>>  set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
>>  set(ENV{PKG_CONFIG_SYSROOT_DIR} $${_HOST_DIR}/$(STAGING_SUBDIR))
>> +# This toolchain file can be used both inside and outside Buildroot.
>> +# * When used inside Buildroot, ccache support is explicitly driven using the
>> +#   USE_CCACHE variable.
>> +# * When used outside Buildroot (i.e. when USE_CCACHE is not defined), ccache
>> +#   support is automatically enabled if the ccache program is available.
>> +if(DEFINED USE_CCACHE)
>> +     if(USE_CCACHE)
>> +             set(CMAKE_ASM_COMPILER $(subst $(HOST_DIR),$${_HOST_DIR},$(TARGET_CROSS))gcc)
>> +             set(CMAKE_C_COMPILER $${_HOST_DIR}/usr/bin/ccache)
>> +             set(CMAKE_CXX_COMPILER $${_HOST_DIR}/usr/bin/ccache)
>> +             set(CMAKE_C_COMPILER_ARG1 $(subst $(HOST_DIR),$${_HOST_DIR},$(TARGET_CROSS))gcc)
>> +             set(CMAKE_CXX_COMPILER_ARG1 $(subst $(HOST_DIR),$${_HOST_DIR},$(TARGET_CROSS))g++)
>> +     else()
>> +             set(CMAKE_C_COMPILER $(subst $(HOST_DIR),$${_HOST_DIR},$(TARGET_CROSS))gcc)
>> +             set(CMAKE_CXX_COMPILER $(subst $(HOST_DIR),$${_HOST_DIR},$(TARGET_CROSS))g++)
>> +     endif()
>
>  I don't see why this USE_CCACHE condition should be dynamic. If
> BR2_CCACHE is set, then we can _always_ use ccache, no? So:
>
> ifeq($(BR2_CCACHE),y)
> define TOOLCHAINFILE_CMAKE_CCACHE
> set(CMAKE_C_COMPILER $${_HOST_DIR}/usr/bin/ccache)
> set(CMAKE_CXX_COMPILER $${_HOST_DIR}/usr/bin/ccache)
> ...
> endef
> else # BR2_CCACHE
> define TOOLCHAINFILE_CMAKE_CCACHE
> ...
> endef
> endif
>

The idea behind this is to always get the same toolchainfile.cmake
generated (except for the target tuple).
In the end we could also use a toolchainfile.cmake.in file, then just
replace the '$(TARGET_CROSS)' using sed.

>
>> +else()
>> +     find_program(CCACHE ccache)
>
>  Note that if we don't set PATH explicitly to point to the host dir, this
> will point to the system's ccache instead of buildroot ccache.

Right, good catch!
I see 2 ways to solve this:
- extend PATH env. var., but this will be valib for all others programs;
- use the HINTS or PATHS option of find_program().
  Funnily, when ccache is available in the system:
  - using find_program(CCACHE ccache HINTS $${_HOST_DIR}/usr/bin) will
find set CCACHE to $${_HOST_DIR}/usr/bin/ccache;
  - whereas find_program(CCACHE ccache PATHS $${_HOST_DIR}/usr/bin)
will find set CCACHE to /usr/bin/ccache

I'll use find_program(... HINTS ...)


Regards,

-- 
Samuel