CMake honors the environment variables CC
and CXX
upon detecting the C and C++ compiler to use:
$ export CC=/usr/bin/clang
$ export CXX=/usr/bin/clang++
$ cmake ..
-- The C compiler identification is Clang
-- The CXX compiler identification is Clang
The compiler specific flags can be overridden by putting them into a make override file and pointing the CMAKE_USER_MAKE_RULES_OVERRIDE
variable to it. Create a file ~/ClangOverrides.txt
with the following contents:
SET (CMAKE_C_FLAGS_INIT "-Wall -std=c99")
SET (CMAKE_C_FLAGS_DEBUG_INIT "-g")
SET (CMAKE_C_FLAGS_MINSIZEREL_INIT "-Os -DNDEBUG")
SET (CMAKE_C_FLAGS_RELEASE_INIT "-O3 -DNDEBUG")
SET (CMAKE_C_FLAGS_RELWITHDEBINFO_INIT "-O2 -g")
SET (CMAKE_CXX_FLAGS_INIT "-Wall")
SET (CMAKE_CXX_FLAGS_DEBUG_INIT "-g")
SET (CMAKE_CXX_FLAGS_MINSIZEREL_INIT "-Os -DNDEBUG")
SET (CMAKE_CXX_FLAGS_RELEASE_INIT "-O3 -DNDEBUG")
SET (CMAKE_CXX_FLAGS_RELWITHDEBINFO_INIT "-O2 -g")
The suffix _INIT
will make CMake initialize the corresponding *_FLAGS
variable with the given value. Then invoke cmake
in the following way:
$ cmake -DCMAKE_USER_MAKE_RULES_OVERRIDE=~/ClangOverrides.txt ..
Finally to force the use of the LLVM binutils, set the internal variable _CMAKE_TOOLCHAIN_PREFIX
. This variable is honored by the CMakeFindBinUtils
module:
$ cmake -D_CMAKE_TOOLCHAIN_PREFIX=llvm- ..
Putting this all together you can write a shell wrapper which sets up the environment variables CC
and CXX
and then invokes cmake
with the mentioned variable overrides.
Also see this CMake FAQ on make override files.
Best Answer
This turns out to be unrelated to CMake:
clang++
uses the system linker by default. For example,uses
/usr/bin/ld
to link the application. To change the linker tollvm-link
, one needs to first emit LLVM byte code, and then call the linker, e.g.:This bypasses
/usr/bin/ld
.