[cfe-users] Need a GCC-free LLVM/Clang on Linux.
Chris Green via cfe-users
cfe-users at lists.llvm.org
Tue Mar 10 07:53:14 PDT 2020
Hi,
On 2/19/20 4:02 PM, Richard Smith wrote:
> I have a two-stage setup that builds a GCC-free Clang except for
> libgcc_s (I've not looked at what's pulling that in yet, but I expect
> that's resolvable).
>
> My stage1 cmake setup has: -DCLANG_DEFAULT_CXX_STDLIB=libc++
> -DCLANG_DEFAULT_RTLIB=compiler-rt
> My stage2 cmake setup additionally
> has: -DLIBCXXABI_USE_LLVM_UNWINDER=ON -DLIBCXXABI_USE_COMPILER_RT=ON
> -DLIBCXX_USE_COMPILER_RT=ON
> (and points CMAKE_C_COMPILER and CMAKE_CXX_COMPILER at the stage1 clang).
Many thanks for this. I got further (I think) but I'm still hitting a
snag (see below).
I'm attempting to use the cache method per the guide (latest caches
attached), and I'm invoking them with:
+ env CC=clang CXX=clang++ cmake -GNinja -C /home/greenc/work/cet-is/test-products/clang/v9_0_1/patch/FNAL.cmake -DCMAKE_INSTALL_PREFIX=/home/greenc/work/cet-is/test-products/clang/v9_0_1/Linux64bit+3.10-2.17 -DBOOTSTRAP_LLVM_CXX_STD=c++17 -S ../../src/clang-9.0.1/llvm -B /home/greenc/work/cet-is/test-products/clang/v9_0_1/build/Linux64bit+3.10-2.17
and
+ cmake --build /home/greenc/work/cet-is/test-products/clang/v9_0_1/build/Linux64bit+3.10-2.17 -j 25 --target stage2 --
where which clang returns:
/home/greenc/work/cet-is/test-products/clang/v7_0_0/Linux64bit+3.10-2.17/bin/clang
and the default C++ standard library for this compiler is libc++.
I'm also attempting to build with C++17 (see command line) to allow for
a later build of flang against the installed new compiler. Eventually I
hope to get all the right components listed to be able to do a
distribution installation such that the installed distribution is
relocatable and able to operate as an SDK against which to compile other
tools such as flang, castxml and include-what-you-use.
I appear to be getting through the compilation of the compiler,
builtins, linker and basic tools (llvm-ar, llvm-nm, /etc./), but I'm
experiencing a failure with the next compilation stage (full log
attached, bzipped to 28K). During the runtimes configuration step I'm
getting a worrying message about ranlib:
/home/greenc/work/cet-is/test-products/clang/v9_0_1/build/Linux64bit+3.10-2.17/bin/llvm-ar: warning: creating t.a
/home/greenc/work/cet-is/test-products/clang/v9_0_1/build/Linux64bit+3.10-2.17/bin/llvm-ranlib: error: Exactly one archive should be specified.
There are a couple of CMake policy warnings (CMP0077), and then when we
try to perform the configure step for "stage2", we get:
-- Check for working CXX compiler: /home/greenc/work/cet-is/test-products/clang/v9_0_1/build/Linux64bit+3.10-2.17/./bin/clang++
-- Check for working CXX compiler: /home/greenc/work/cet-is/test-products/clang/v9_0_1/build/Linux64bit+3.10-2.17/./bin/clang++ -- broken
CMake Error at /home/greenc/work/cet-is/test-products/cmake/v3_14_3/Linux64bit+3.10-2.17/share/cmake-3.14/Modules/CMakeTestCXXCompiler.cmake:53 (message):
The C++ compiler
"/home/greenc/work/cet-is/test-products/clang/v9_0_1/build/Linux64bit+3.10-2.17/./bin/clang++"
is not able to compile a simple test program.
It fails with the following output:
Change Dir: /home/greenc/work/cet-is/test-products/clang/v9_0_1/build/Linux64bit+3.10-2.17/tools/clang/stage2-bins/CMakeFiles/CMakeTmp
Run Build Command(s):/home/greenc/work/cet-is/test-products/ninja/v1_10_0/Linux64bit+3.10-2.17/bin/ninja cmTC_f1b67
[1/2] Building CXX object CMakeFiles/cmTC_f1b67.dir/testCXXCompiler.cxx.o
[2/2] Linking CXX executable cmTC_f1b67
FAILED: cmTC_f1b67
: && /home/greenc/work/cet-is/test-products/clang/v9_0_1/build/Linux64bit+3.10-2.17/./bin/clang++ -fno-stack-protector -fno-common -Wno-profile-instr-unprofiled CMakeFiles/cmTC_f1b67.dir/testCXXCompiler.cxx.o -o cmTC_f1b67 && :
/usr/bin/ld: cannot find -lc++
Indeed, libc++ has not been built.
I'm obviously doing something silly, but I'm not able to ascertain from
the documentation what it might be. I'll try again with a modern GCC
(I'm on Scientific Linux 7, so the native GCC 4.8.5 is insufficient)
just in case the Clang compiler is not recent enough to handle this, but
I'm not optimistic. Any pointers you can give me would be very much
appreciated.
Thanks for any help,
Chris.
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# This file sets up a CMakeCache for a simple distribution bootstrap build.
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endif()
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