I started studying cmake
about 2 weeks ago and like it. Thus far, I have been successful in building and packaging (with the native system packaging format) libc++abi
, libc++
, llvm
3.4 all with cmake
(libc++abi
with my own cmake
setup) for RHEL 6.x, Fedora 20+, and Ubuntu 12.04 LTS+.
I would like to create a C++ build environment that
- Frees us from dependency on GNU GCC and
libstdc++
completely (thus we don't want any LLVM RPM/DEB from these aforementioned distros or the LLVM Debian/Ubuntu nightly packages download site)
- Enables us to explore fully C++11 and C++1y. In other words, we can try even the bleeding edge LLVM/clang anytime we want to while keeping all our build systems clean with package management systems.
Nevertheless, I hit a snag in attempting to build clang
3.4 with cmake
, on a build host running Ubuntu 12.04 LTS 64bit, with a pure clang 3.3 built by me without any dependency on GNU libstdc++
, together with libc++
3.3 and libc++abi
. The later two have no libstdc++
dependency either. I built both that way too.
I know of the Clang - Getting Started Web page really well and have used the instructions there successfully. But these are exactly what I don't want to use. They are incorrect too: the CMakeLists.txt
of clang
3.4 clearly states the following:
1 # If we are not building as a part of LLVM, build Clang as an
2 # standalone project, using LLVM as an external library:
3 if( CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR )
4 project(Clang)
5 cmake_minimum_required(VERSION 2.8)
6
7 set(CLANG_PATH_TO_LLVM_SOURCE "" CACHE PATH
8 "Path to LLVM source code. Not necessary if using an installed LLVM.")
9 set(CLANG_PATH_TO_LLVM_BUILD "" CACHE PATH
10 "Path to the directory where LLVM was built or installed.")
See line 1 and 2. But, I have not found any LLVM documentation regarding how to set the CLANG_PATH_TO_LLVM_BUILD
. I tried the following:
cmake -DCLANG_PATH_TO_LLVM_BUILD="../../llvm-3.4/build" ..
and got the following errors:
$ clang3.4/_tars/clang-3.4/build$ cmake -DCLANG_PATH_TO_LLVM_BUILD="../../llvm-3.4/build" ..
-- The C compiler identification is Clang 3.3.0
-- The CXX compiler identification is Clang 3.3.0
-- Check for working C compiler: /usr/bin/clang
-- Check for working C compiler: /usr/bin/clang -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/clang++
-- Check for working CXX compiler: /usr/bin/clang++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
CMake Error at CMakeLists.txt:39 (include):
include could not find load file:
AddLLVM
CMake Error at CMakeLists.txt:40 (include):
include could not find load file:
TableGen
-- Performing Test C_SUPPORTS_FLAG
-- Performing Test C_SUPPORTS_FLAG - Success
-- Performing Test CXX_SUPPORTS_FLAG
-- Performing Test CXX_SUPPORTS_FLAG - Success
-- Building with -fPIC
-- Performing Test SUPPORTS_FVISIBILITY_INLINES_HIDDEN_FLAG
-- Performing Test SUPPORTS_FVISIBILITY_INLINES_HIDDEN_FLAG - Success
-- Found LibXml2: /usr/lib/x86_64-linux-gnu/libxml2.so (found version "2.7.8")
-- Clang version: 3.4
-- Performing Test CXX_SUPPORTS_NO_NESTED_ANON_TYPES_FLAG
-- Performing Test CXX_SUPPORTS_NO_NESTED_ANON_TYPES_FLAG - Success
CMake Error at utils/TableGen/CMakeLists.txt:3 (add_tablegen):
Unknown CMake command "add_tablegen".
-- Configuring incomplete, errors occurred!
But that's not right! The LLVM + compiler-rt
has been installed on the build host with our own DEB
. And,
$ llvm/clang3.4/_tars/clang-3.4/build$ ls /usr/share/llvm/cmake
AddLLVM.cmake ChooseMSVCCRT.cmake linux_issue.cmake LLVMConfigVersion.cmake pkg.cmake
AddLLVMDefinitions.cmake GetSVN.cmake LLVM-Config.cmake LLVMParseArguments.cmake TableGen.cmake
arch.cmake HandleLLVMOptions.cmake LLVMConfig.cmake LLVMProcessSources.cmake
So, all required cmake
modules are there - right on the system!
I would appreciate a hint as to how to coerce clang
3.4 to build with cmake
, with an already installed LLVM 3.4 + compiler-rt
3.4.
Update:
I decided to do the following:
$ llvm/clang3.4/_tars/clang-3.4/build$ cmake -DCLANG_PATH_TO_LLVM_BUILD="/usr" ..
-- Building with -fPIC
-- Clang version: 3.4
-- Found Subversion: /usr/bin/svn (found version "1.6.17")
-- Configuring done
-- Generating done
-- Build files have been written to: ../llvm/clang3.4/_tars/clang-3.4/build
../llvm/clang3.4/_tars/clang-3.4/build$ make -j 2
Scanning dependencies of target ClangDriverOptions
Scanning dependencies of target clang-tblgen
[ 0%] Building Options.inc...
[ 0%] ../llvm/clang3.4/_tars/clang-3.4/include/clang/Driver/Options.td:15:9: error: Could not find include file 'llvm/Option/OptParser.td'
include "llvm/Option/OptParser.td"
^
.../llvm/clang3.4/_tars/clang-3.4/include/clang/Driver/Options.td:15:9: Building CXX object utils/TableGen/CMakeFiles/clang-tblgen.dir/ClangASTNodesEmitter.cpp.o
error: Unexpected input at top level
include "llvm/Option/OptParser.td"
^
make[2]: *** [include/clang/Driver/Options.inc.tmp] Error 1
make[1]: *** [include/clang/Driver/CMakeFiles/ClangDriverOptions.dir/all] Error 2
make[1]: *** Waiting for unfinished jobs....
[ 0%] Building CXX object utils/TableGen/CMakeFiles/clang-tblgen.dir/ClangAttrEmitter.cpp.o
[ 0%] Building CXX object utils/TableGen/CMakeFiles/clang-tblgen.dir/ClangCommentCommandInfoEmitter.cpp.o
[ 0%] Building CXX object utils/TableGen/CMakeFiles/clang-tblgen.dir/ClangCommentHTMLNamedCharacterReferenceEmitter.cpp.o
[ 1%] Building CXX object utils/TableGen/CMakeFiles/clang-tblgen.dir/ClangCommentHTMLTagsEmitter.cpp.o
[ 1%] Building CXX object utils/TableGen/CMakeFiles/clang-tblgen.dir/ClangDiagnosticsEmitter.cpp.o
[ 1%] Building CXX object utils/TableGen/CMakeFiles/clang-tblgen.dir/ClangSACheckersEmitter.cpp.o
[ 1%] Building CXX object utils/TableGen/CMakeFiles/clang-tblgen.dir/NeonEmitter.cpp.o
[ 1%] Building CXX object utils/TableGen/CMakeFiles/clang-tblgen.dir/TableGen.cpp.o
Linking CXX executable ../llvm/clang3.4/_tars/llvm-3.4/build/bin/clang-tblgen
[ 1%] Built target clang-tblgen
make: *** [all] Error 2
That's better. Looks like clang
3.4's default CMakeLists.txt
is not even QA-ed x-( Yikes x-(