package/pkg-cmake: Use CMAKE_<LANG>_COMPILER_LAUNCHER for ccache

Since cmake version 3.4.3 CMAKE_<LANG>_COMPILER_LAUNCHER is used as the way to invoke things like ccache. We set this to ccache for the host and for cross compilers in toolchain.cmake.in. This leaves CMAKE_<C,CXX>_COMPILER pointing at the real compiler and still uses ccache.

ref: https://cmake.org/cmake/help/v3.4/variable/CMAKE_LANG_COMPILER_LAUNCHER.html

Since cmake version 3.4.0 CMAKE_<LANG>_COMPILER_LAUNCHER is used as the way to invoke things like ccache. We set this to ccache for the host and for cross compilers in toolchain.cmake.in. This leaves CMAKE_<C,CXX>_COMPILER pointing at the real compiler and still uses ccache.

Update minimium dependency version in check-host-cmake.mk accordingly.

ref: https://cmake.org/cmake/help/v3.4/variable/CMAKE_LANG_COMPILER_LAUNCHER.html

Signed-off-by Daniel Black <[email protected]>

---
 package/pkg-cmake.mk                     | 22 ++++++----------------
 support/dependencies/check-host-cmake.mk |  2 +-
 support/misc/toolchainfile.cmake.in      |  2 ++
 3 files changed, 9 insertions(+), 17 deletions(-)

package/pkg-cmake.mk +6 -16

index 5d0a455..e2590b7 100644
@@ -20,17 +20,6 @@
 #
 ################################################################################
 
-# Set compiler variables.
-ifeq ($(BR2_CCACHE),y)
-CMAKE_HOST_C_COMPILER = $(HOST_DIR)/usr/bin/ccache
-CMAKE_HOST_CXX_COMPILER = $(HOST_DIR)/usr/bin/ccache
-CMAKE_HOST_C_COMPILER_ARG1 = $(HOSTCC_NOCCACHE)
-CMAKE_HOST_CXX_COMPILER_ARG1 = $(HOSTCXX_NOCCACHE)
-else
-CMAKE_HOST_C_COMPILER = $(HOSTCC)
-CMAKE_HOST_CXX_COMPILER = $(HOSTCXX)
-endif
-
 ifneq ($(QUIET),)
 CMAKE_QUIET = -DCMAKE_RULE_MESSAGES=OFF -DCMAKE_INSTALL_MESSAGE=NEVER
 endif

@@ -120,11 +109,11 @@ define $(2)_CONFIGURE_CMDS
 		-DCMAKE_CXX_FLAGS="$$(HOST_CXXFLAGS)" \
 		-DCMAKE_EXE_LINKER_FLAGS="$$(HOST_LDFLAGS)" \
 		-DCMAKE_ASM_COMPILER="$$(HOSTAS)" \
-		-DCMAKE_C_COMPILER="$$(CMAKE_HOST_C_COMPILER)" \
-		-DCMAKE_CXX_COMPILER="$$(CMAKE_HOST_CXX_COMPILER)" \
-		$(if $$(CMAKE_HOST_C_COMPILER_ARG1),\
-			-DCMAKE_C_COMPILER_ARG1="$$(CMAKE_HOST_C_COMPILER_ARG1)" \
-			-DCMAKE_CXX_COMPILER_ARG1="$$(CMAKE_HOST_CXX_COMPILER_ARG1)" \
+		-DCMAKE_C_COMPILER="$$(HOSTCC_NOCCACHE)" \
+		-DCMAKE_CXX_COMPILER="$$(HOSTCXX_NOCCACHE)" \
+		$(if $(BR2_CCACHE),\
+			-DCMAKE_CXX_COMPILER_LAUNCHER="$$(HOST_DIR)/usr/bin/ccache" \
+			-DCMAKE_C_COMPILER_LAUNCHER="$$(HOST_DIR)/usr/bin/ccache" \
 		) \
 		-DCMAKE_COLOR_MAKEFILE=OFF \
 		-DBUILD_DOC=OFF \

@@ -247,6 +236,7 @@ $(HOST_DIR)/usr/share/buildroot/toolchainfile.cmake:
 		-e 's#@@CMAKE_SYSTEM_PROCESSOR@@#$(call qstrip,$(CMAKE_SYSTEM_PROCESSOR))#' \
 		-e 's#@@TOOLCHAIN_HAS_FORTRAN@@#$(if $(BR2_TOOLCHAIN_HAS_FORTRAN),1,0)#' \
 		-e 's#@@CMAKE_BUILD_TYPE@@#$(if $(BR2_ENABLE_DEBUG),Debug,Release)#' \
+		-e 's#\([^@]*\)@@CCACHE@@#$(if $(BR2_CCACHE),\1/usr/bin/ccache,\#\1)#g' \
 		$(TOPDIR)/support/misc/toolchainfile.cmake.in \
 		> $@
 

support/dependencies/check-host-cmake.mk +1 -1

index 8002278..21f5072 100644
@@ -8,7 +8,7 @@
 # package is bumped or a new one added, and it requires a higher
 # version, our cmake infra will catch it and whine.
 #
-BR2_CMAKE_VERSION_MIN = 3.1
+BR2_CMAKE_VERSION_MIN = 3.4
 
 BR2_CMAKE ?= cmake
 ifeq ($(call suitable-host-package,cmake,\

support/misc/toolchainfile.cmake.in +2 -0

index c38800e..c4086ab 100644
@@ -60,6 +60,8 @@ set(ENV{PKG_CONFIG_SYSROOT_DIR} "${RELOCATED_HOST_DIR}/@@STAGING_SUBDIR@@")
 # This toolchain file can be used both inside and outside Buildroot.
 set(CMAKE_C_COMPILER "${RELOCATED_HOST_DIR}/@@TARGET_CC@@")
 set(CMAKE_CXX_COMPILER "${RELOCATED_HOST_DIR}/@@TARGET_CXX@@")
+set(CMAKE_C_COMPILER_LAUNCHER "${RELOCATED_HOST_DIR}/@@CCACHE@@")
+set(CMAKE_CXX_COMPILER_LAUNCHER "${RELOCATED_HOST_DIR}/@@CCACHE@@")
 if(@@TOOLCHAIN_HAS_FORTRAN@@)
   set(CMAKE_Fortran_FLAGS_DEBUG "" CACHE STRING "Debug Fortran FLAGS")
   set(CMAKE_Fortran_FLAGS_RELEASE " -DNDEBUG" CACHE STRING "Release Fortran FLAGS")

Quoted 6 lines · Daniel Black

Since cmake version 3.4.0 CMAKE_<LANG>_COMPILER_LAUNCHER is used as the way to invoke things like ccache. We set this to ccache for the host and for cross compilers in toolchain.cmake.in. This leaves CMAKE_<C,CXX>_COMPILER pointing at the real compiler and still uses ccache.

Quoted 1 line

Update minimium dependency version in check-host-cmake.mk accordingly.

This is very unfortunate, it means a substantial slowdown in the build for
people who have an older system CMake.

Although it is indeed cleaner to handle ccache this way, I don't think it
really fixes anything, does it?

In that case, I think we should just stick with
the old way of doing things. We can revisit when we need to CMake 3.4 for some other package.

Quoted 11 lines · Daniel Black

Quoted 7 lines

Since cmake version 3.4.0 CMAKE_<LANG>_COMPILER_LAUNCHER is used as the way to invoke things like ccache. We set this to ccache for the host and for cross compilers in toolchain.cmake.in. This leaves CMAKE_<C,CXX>_COMPILER pointing at the real compiler and still uses ccache.

Update minimium dependency version in check-host-cmake.mk accordingly.

This is very unfortunate, it means a substantial slowdown in the build for
people who have an older system CMake.

I didn't think it was that substantial for a one-off host package upgrade. I do realize it is a non-zero imposition for that installed cmake before it was updated to 3.4.0 in 7453c4bf6010b3a8dd794c39e327641abea15503 (Nov 13 2015).

Quoted 2 lines

Although it is indeed cleaner to handle ccache this way, I don't think it
really fixes anything, does it?

Might fix some subtle build errors for packages that do odd things however no, there isn't an definite breakage I can point to.

Quoted 3 lines

In that case, I think we should just stick with
the old way of doing things. We can revisit when we need to CMake 3.4 for some other package.

Works for me.

Hi Daniel,

Quoted 6 lines · Daniel Black

Since cmake version 3.4.3 CMAKE_<LANG>_COMPILER_LAUNCHER is used as the way to invoke things like ccache. We set this to ccache for the host and for cross compilers in toolchain.cmake.in. This leaves CMAKE_<C,CXX>_COMPILER pointing at the real compiler and still uses ccache.

Quoted 1 line

ref: https://cmake.org/cmake/help/v3.4/variable/CMAKE_LANG_COMPILER_LAUNCHER.html

Currently the oldest version of host installed cmake version that Buildroot supports is 3.1. If the dependency checker finds cmake 3.1 and newer installed on the host, Buildroot will use it. For your patch to work, you need to bump the minimum to 3.4.3. See support/dependencies/check-host-cmake.mk.