[llvm-dev] Building LLVM and Clang using Clang?

[Greg Stark via llvm-dev]

Try as I might I can't seem to get LLVM to bulid using clang/clang++.
No matter what I do it insists on using /usr/bin/cc and /usr/bin/c++
which are gcc. Am I missing something obvious? I vaguely remember some
document describing a stage1 compiler built by your old toolchain and
a stage2 compiler but I can't find the steps to do that any more.


$ CC=/usr/local/bin/clang CXX=/usr/local/bin/clang++  cmake
-DCMAKE_BUILD_TYPE=Release -Wno-dev ~/src/llvm
-- Target triple: x86_64-unknown-linux-gnu
-- Native target architecture is X86
-- Threads enabled.
-- Doxygen disabled.
-- Sphinx disabled.
-- Go bindings disabled.
-- Could NOT find OCaml (missing:  OCAMLFIND OCAML_VERSION OCAML_STDLIB_PATH)
-- Could NOT find OCaml (missing:  OCAMLFIND OCAML_VERSION OCAML_STDLIB_PATH)
-- OCaml bindings disabled.
-- Building with -fPIC
-- Constructing LLVMBuild project information
-- Targeting AArch64
-- Targeting AMDGPU
-- Targeting ARM
-- Targeting BPF
-- Targeting CppBackend
-- Targeting Hexagon
-- Targeting Mips
-- Targeting MSP430
-- Targeting NVPTX
-- Targeting PowerPC
-- Targeting Sparc
-- Targeting SystemZ
-- Targeting X86
-- Targeting XCore
-- Compiler-RT supported architectures: x86_64
-- Clang version: 3.8.0
-- Configuring done
-- Generating done
-- Build files have been written to: /home/stark/src/llvm-build
$ make CC=/usr/local/bin/clang CXX=/usr/local/bin/clang++
[  0%] Building CXX object lib/Support/CMakeFiles/LLVMSupport.dir/APFloat.cpp.o
[  0%] Building CXX object lib/Support/CMakeFiles/LLVMSupport.dir/APInt.cpp.o
[  0%] Building CXX object lib/Support/CMakeFiles/LLVMSupport.dir/APSInt.cpp.o
[  0%] Building CXX object
lib/Support/CMakeFiles/LLVMSupport.dir/ARMBuildAttrs.cpp.o
[  0%] Building CXX object lib/Support/CMakeFiles/LLVMSupport.dir/ARMWinEH.cpp.o
[  0%] Building CXX object
lib/Support/CMakeFiles/LLVMSupport.dir/Allocator.cpp.o
[  0%] Building CXX object
lib/Support/CMakeFiles/LLVMSupport.dir/BlockFrequency.cpp.o

And while doing that I ran this and see it's running /usr/bin/c++:

$ ps auxww | grep LLVMSupp
stark    26435  0.1  0.0  10400  2744 pts/6    S+   18:50   0:00 make
-f lib/Support/CMakeFiles/LLVMSupport.dir/build.make
lib/Support/CMakeFiles/LLVMSupport.dir/build
stark    26463  0.0  0.0   4328   752 pts/6    S+   18:50   0:00
/bin/sh -c cd /home/stark/src/llvm-build/lib/Support && /usr/bin/c++
-DGTEST_HAS_RTTI=0 -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS
-D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -fPIC
-fvisibility-inlines-hidden -Wall -W -Wno-unused-parameter
-Wwrite-strings -Wcast-qual -Wno-missing-field-initializers -pedantic
-Wno-long-long -Wno-maybe-uninitialized -Wnon-virtual-dtor
-Wno-comment -std=c++11 -ffunction-sections -fdata-sections -O3
-DNDEBUG -fPIC -I/home/stark/src/llvm-build/lib/Support
-I/home/stark/src/llvm/lib/Support
-I/home/stark/src/llvm-build/include -I/home/stark/src/llvm/include
 -fno-exceptions -fno-rtti -o
CMakeFiles/LLVMSupport.dir/ARMBuildAttrs.cpp.o -c
/home/stark/src/llvm/lib/Support/ARMBuildAttrs.cpp
stark    26464  0.0  0.0  11512   996 pts/6    S+   18:50   0:00
/usr/bin/c++ -DGTEST_HAS_RTTI=0 -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS
-D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -fPIC
-fvisibility-inlines-hidden -Wall -W -Wno-unused-parameter
-Wwrite-strings -Wcast-qual -Wno-missing-field-initializers -pedantic
-Wno-long-long -Wno-maybe-uninitialized -Wnon-virtual-dtor
-Wno-comment -std=c++11 -ffunction-sections -fdata-sections -O3
-DNDEBUG -fPIC -I/home/stark/src/llvm-build/lib/Support
-I/home/stark/src/llvm/lib/Support
-I/home/stark/src/llvm-build/include -I/home/stark/src/llvm/include
-fno-exceptions -fno-rtti -o
CMakeFiles/LLVMSupport.dir/ARMBuildAttrs.cpp.o -c
/home/stark/src/llvm/lib/Support/ARMBuildAttrs.cpp
stark    26465  0.0  1.2  88756 48740 pts/6    R+   18:50   0:00
/usr/lib/gcc/x86_64-linux-gnu/5/cc1plus -quiet -I
/home/stark/src/llvm-build/lib/Support -I
/home/stark/src/llvm/lib/Support -I /home/stark/src/llvm-build/include
-I /home/stark/src/llvm/include -imultiarch x86_64-linux-gnu
-D_GNU_SOURCE -D GTEST_HAS_RTTI=0 -D _GNU_SOURCE -D
__STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS
-D NDEBUG /home/stark/src/llvm/lib/Support/ARMBuildAttrs.cpp -quiet
-dumpbase ARMBuildAttrs.cpp -mtune=generic -march=x86-64
-auxbase-strip CMakeFiles/LLVMSupport.dir/ARMBuildAttrs.cpp.o -O3
-Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual
-Wno-missing-field-initializers -Wpedantic -Wno-long-long
-Wno-maybe-uninitialized -Wnon-virtual-dtor -Wno-comment -std=c++11
-fvisibility-inlines-hidden -ffunction-sections -fdata-sections -fPIC
-fno-exceptions -fno-rtti -o /tmp/ccTTfqUE.s
stark    26467  0.0  0.0  14452   932 pts/3    S+   18:50   0:00 grep LLVMSupp


-- 
greg