Using Xcode to compile clang, still possible ?

Clang Frontend
1

Hi

as a clang newbie, I used the „Getting Started“ (http://clang.llvm.org/get_started.html) documentation and I could build everything nicely using cmake. I was also able to create a LLVM.xcodeproj file. But that project is huge.

Judging from an older blog entry (http://www.stuartcarnie.com/2012/06/llvm-clang-hacking-part-1.html), it should also be possible to just create a clang.xcodeproj file, which would be much preferable to me, but I can’t get it to work.

I set this environment variables to get llvm-config to be found

PATH=`pwd`/build/bin:`pwd`/build/tools:$PATH
export PATH

But then I get

walitza:clang nat$ cmake -DCLANG_PATH_TO_LLVM_SOURCE=../llvm -DCLANG_PATH_TO_LLVM_BUILD=../build -DCMAKE_BUILD_TYPE=Debug ../llvm/tools/clang
-- Found LLVM_CONFIG as /Volumes/Source/srcM/clang-test/build/bin/llvm-config
-- Building with -fPIC
-- Clang version: 3.6.0
CMake Error at /Volumes/Source/srcM/clang-test/build/share/llvm/cmake/AddLLVM.cmake:438 (add_executable):
  add_executable cannot create target "clang-tblgen" because an imported
  target with the same name already exists.
Call Stack (most recent call first):
  /Volumes/Source/srcM/clang-test/build/share/llvm/cmake/AddLLVM.cmake:501 (add_llvm_executable)
  /Volumes/Source/srcM/clang-test/build/share/llvm/cmake/TableGen.cmake:76 (add_llvm_utility)
  utils/TableGen/CMakeLists.txt:3 (add_tablegen)

CMake Error at /Volumes/Source/srcM/clang-test/build/share/llvm/cmake/LLVM-Config.cmake:49 (target_link_libraries):
  Cannot specify link libraries for target "clang-tblgen" which is not built
  by this project.
Call Stack (most recent call first):
  /Volumes/Source/srcM/clang-test/build/share/llvm/cmake/LLVM-Config.cmake:34 (explicit_llvm_config)
  /Volumes/Source/srcM/clang-test/build/share/llvm/cmake/AddLLVM.cmake:455 (llvm_config)
  /Volumes/Source/srcM/clang-test/build/share/llvm/cmake/AddLLVM.cmake:501 (add_llvm_executable)
  /Volumes/Source/srcM/clang-test/build/share/llvm/cmake/TableGen.cmake:76 (add_llvm_utility)
  utils/TableGen/CMakeLists.txt:3 (add_tablegen)

-- Configuring incomplete, errors occurred!
See also "/Volumes/Source/srcM/clang-test/clang/CMakeFiles/CMakeOutput.log".
See also "/Volumes/Source/srcM/clang-test/clang/CMakeFiles/CMakeError.log“.

Doesn’t that work anymore ?

Ciao
   Nat!

2

It looks like you are trying to use the so-called “standalone” clang build, but you checked out clang into llvm/tools/clang. You only need to put clang sources in llvm/tools/clang if you want it to be part of the LLVM build. If you move the sources out to somewhere alongside the llvm sources, the standalone build will probably work. I did this with VS a few weeks ago.

Also, you probably want to delete your initial llvm build directory before retrying, because it will probably contain variables defined by clang’s cmake that shouldn’t be there.

3

Thanks, that was very helpful and it got me further along the way.

Unfortunately I am also a cmake newbie as well...

I moved llvm/tools/clang away and built llvm again. Then I tried to build clang separately in its own build directory thusly:

nat@kempe:build(^) $ cmake -DCLANG_PATH_TO_LLVM_SOURCE=../../clang-test/llvm -DCLANG_PATH_TO_LLVM_BUILD=../../clang-test/build -DCMAKE_BUILD_TYPE=Debug ../clang
-- Found LLVM_CONFIG as /Volumes/Source/srcM/clang-test/build/bin/llvm-config
CMake Error at /Volumes/Source/srcM/clang-test/build/share/llvm/cmake/HandleLLVMOptions.cmake:38 (message):
  Host Clang must be able to find libstdc++4.7 or newer!
Call Stack (most recent call first):
  CMakeLists.txt:96 (include)

-- Configuring incomplete, errors occurred!
See also "/Volumes/Source/srcM/mulle-clang/build/CMakeFiles/CMakeOutput.log".
See also "/Volumes/Source/srcM/mulle-clang/build/CMakeFiles/CMakeError.log".

On a hunch (http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20140106/200545.html) I edited - in the llvm build directory "./../clang-test/build/" - the "CMakeCache.txt" file for LLVM_ENABLE_LIBCXX:BOOL=ON and cmaked/build all of llvm.

But the same error persists, probably because I don't understand how cmake works.

Ciao
   Nat!

4

Are you sure those cmake variables are ok? If I move clang out of source and try to configure using cmake gui I can’t see any variables with CLANG_ prefix?

5

I am not sure at all, I am just parroting what I gleaned from that blog entry I mentioned in my first posting.

But when I just do

cmake ../clang

the error message is the same. (I have to build llvm anyway it seems, because otherwise I don't get llvm-config.)

Ciao
   Nat!

6

I did this a number of times on windows and linux and I don’t remember using those variables. What happens if you remove them? I think you’ll need to specify build type and path to llvm-config…

7

Ok, having experimented a bit, llvm-config seems to provide the compiler flags needed for the clang build. So specifying those additional CLANG_ variables is maybe superflous, but maybe not. The Xcode installation itself unfortunately does not seem to provide a llvm-config (I couldn't find any).

nat@kempe:build(^) $ ../../clang-test/build/bin/llvm-config --cxxflags
-I/Volumes/Source/srcM/clang-test/llvm/include -I/Volumes/Source/srcM/clang-test/build/include -stdlib=libc++ -fPIC -fvisibility-inlines-hidden -Wall -W -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -pedantic -Wno-long-long -Wcovered-switch-default -std=c++11 -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS

Ciao
   Nat!

8

So for anyone trying the same, the solution for me was this:

mkdir build-llvm
cd build-llvm
cmake -G "Unix Makefiles" -DLLVM_ENABLE_CXX1Y:BOOL=OFF ../llvm
make
cd ..

PATH=`pwd`/build-llvm/bin:$PATH ; export PATH

mkdir build-clang
cd build-clang
cmake -G "Xcode" ../clang

Ciao
   Nat!