On 01/07/2012 12:56 AM, Paweł Sikora wrote:
Hi,
i'm trying to setup a toolchain file for cross-compilation with target specfic
options and afaics cmake dosen't use flags from such file:
$ cat CMakeLists.txt
cmake_minimum_required( VERSION 2.8.7 )
project( test CXX )
add_executable( main main.cpp )
$ cat CMakeToolchain-x86_64-gnu-linux.txt
set( CMAKE_SYSTEM_NAME Linux )
set( CMAKE_SYSTEM_VERSION 1 )
set( CMAKE_CXX_COMPILER
/local/devel/toolchain46/x86_64-gnu-linux/bin/x86_64-gnu-linux-g++ )
set( CMAKE_CXX_FLAGS -Wall -O1 -gdwarf-4 -g2 -std=gnu++0x )
set( CMAKE_FIND_ROOT_PATH /usr )
$ LANG=C sh -x ./build.sh
+ rm -rf build
+ mkdir build
+ cd build
+ cmake ../ -DCMAKE_TOOLCHAIN_FILE=../CMakeToolchain-x86_64-gnu-linux.txt
-- The CXX compiler identification is GNU
-- Check for working CXX compiler:
/local/devel/toolchain46/x86_64-gnu-linux/bin/x86_64-gnu-linux-g++
-- Check for working CXX compiler:
/local/devel/toolchain46/x86_64-gnu-linux/bin/x86_64-gnu-linux-g++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Configuring done
-- Generating done
(...)
[100%] Building CXX object CMakeFiles/main.dir/main.cpp.o
/local/devel/toolchain46/x86_64-gnu-linux/bin/x86_64-gnu-linux-g++ -o
CMakeFiles/main.dir/main.cpp.o -c
/home/users/pluto/src/cmake-cross-build/main.cpp
^^^ no cxx
flags.
is it a bug or a feature?
BR,
Paweł.
Try SET(CMAKE_CXX_FLAGS ... CACHE STRING ...) in the toolchain
file, and cf. [1]. AFAIK, the toolchain file is processed first,
but later in CMakeCXXInformation.cmake:
# Load compiler-specific information.
IF(CMAKE_CXX_COMPILER_ID)
INCLUDE(Compiler/${CMAKE_CXX_COMPILER_ID}-CXX OPTIONAL)
ENDIF(CMAKE_CXX_COMPILER_ID)
This loads Compiler/GNU-CXX.cmake and subsequently Compiler/GNU.cmake
which empties CMAKE_CXX_FLAGS_INIT. Again later in the same file:
# add the flags to the cache based
# on the initial values computed in the platform/*.cmake files
# use _INIT variables so that this only happens the first time
# and you can set these flags in the cmake cache
SET(CMAKE_CXX_FLAGS_INIT $ENV{CXXFLAGS} ${CMAKE_CXX_FLAGS_INIT})
# avoid just having a space as the initial value for the cache
IF(CMAKE_CXX_FLAGS_INIT STREQUAL )
SET(CMAKE_CXX_FLAGS_INIT)
ENDIF(CMAKE_CXX_FLAGS_INIT STREQUAL )
SET (CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS_INIT} CACHE STRING
Flags used by the compiler during all build types.)
If CMAKE_CXX_FLAGS is not cached by that time, the SET() command sets
this variable to CMAKE_CXX_FLAGS_INIT, both in the cache *and* in the
current scope, thus overwriting the value from the toolchain file and
having CMAKE_CXX_FLAGS be empty. Already writing it to the cache in
the toolchain file makes the incriminated SET() command a no-op, so
the desired value will survive. However, I'm not completely sure if
this is the intended way to handle language flags when they are to
be preset in a toolchain file.
Regards,
Michael
[1] http://www.mail-archive.com/cmake@cmake.org/msg33240.html
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