Building and packaging LLVM clang 3.4 with cmake

Question

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

1. 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)
2. 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-(

Answer 1

I decided to tough it out as any self-respecting engineer would do :) I simply vi-ed the following two files and add full path to the offending include, and then that's that.

1. Options.td
2. CC1AsOptions.td

Now I can build all desired LLVM main projects without libstdc++ dependency, all linked with libc++ and libc++abi. Hooray :)

So, I have confirmed that

• Some instructions given in Getting Started: Building and Running Clang are misleading, e.g. 7.
• All main LLVM projects (except compiler-rt AFAIK) can be built with cmake. There is no need to lump them together under the LLVM source tree for building. You definitely can build nearly all of them separately on Linux, unlike what these "official" documentation may lead you to believe :>

The LLVM team should really think through and minimize the apparent cyclic dependency among all projects. Bootstrapping LLVM/clang on various Linux distros (especially older ones such as RHEL 5.x) without GNU libstdc++ dependency is too tedious - speaking from my first hand experience. They can be done (I have done it :) but it's not for the faint of heart.

Answer 2

I think this project does what you're trying to do:

https://github.com/rsmmr/install-clang

I've used it on FC16+, but did run into bootstrapping issues on RHEL5.x.