Clang 9.0.0 rc1 Wrong generation of constexpr symbol causes bootstrapping to fail #42188
Description
| Bugzilla Link | 42843 |
| Resolution | FIXED |
| Resolved on | Sep 25, 2019 04:12 |
| Version | 9.0 |
| OS | Windows NT |
| Blocks | #41819 |
| Reporter | LLVM Bugzilla Contributor |
| CC | @zmodem,@zygoloid,@rnk,@StephanTLavavej |
Extended Description
I used Visual Studio 16.2 as the build environment for clang and downloaded the pre-compiled http://prereleases.llvm.org/9.0.0/rc1/LLVM-9.0.0-rc1-win64.exe using 7z to extract to the appropriate directory. Then use it to build the llvm release/9.x branch and get the following error:
lld-link: error: duplicate symbol: bool const std::_Is_integral in utils\TableGen\CMakeFiles\llvm-tblgen.dir\AsmMatcherEmitter.cpp.obj and in utils\TableGen\CMakeFiles\llvm-tblgen.dir\AsmWriterEmitter.cpp.obj
msvc version: 14.22.27905
I built llvm 9.0 successfully using clang-cl 8.0.1 + Visual Studio 16.2.
cmake args:
cmake -GNinja "F:/Clangbuilder/out/release_9.x/llvm" -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_ASSERTIONS=OFF -DCMAKE_INSTALL_UCRT_LIBRARIES=ON -DLLVM_TARGETS_TO_BUILD="X86;AArch64;ARM" -DLLVM_EXPERIMENTAL_TARGETS_TO_BUILD="RISCV;WebAssembly" -DLLVM_ENABLE_PROJECTS="clang;clang-tools-extra;compiler-rt;lld;lldb;libcxx" -DLLVM_FORCE_BUILD_RUNTIME=ON -DLIBCXX_ENABLE_SHARED=YES -DLIBCXX_ENABLE_STATIC=YES -DLIBCXX_ENABLE_EXPERIMENTAL_LIBRARY=NO -DLIBCXX_HAS_WIN32_THREAD_API=ON -DLIBCXX_STANDARD_VER="c++17" -DCMAKE_INSTALL_PREFIX="F:/Clangbuilder/bin/utils/llvm" -DLLDB_RELOCATABLE_PYTHON=1 -DLLDB_DISABLE_PYTHON=1 -DCMAKE_C_COMPILER="F:/Clangbuilder/bin/utils/LLVM-9.0.0-rc1-win64/bin/clang-cl.exe" -DCMAKE_CXX_COMPILER="F:/Clangbuilder/bin/utils/LLVM-9.0.0-rc1-win64/bin/clang-cl.exe" -DCMAKE_CXX_FLAGS="-fms-compatibility-version=19.22 -m64 " -DCMAKE_C_FLAGS="-fms-compatibility-version=19.22 -m64 " -DLLVM_ENABLE_LTO=Thin -DCMAKE_LINKER="F:/Clangbuilder/bin/utils/LLVM-9.0.0-rc1-win64/bin/lld-link.exe" -DCMAKE_AR="F:/Clangbuilder/bin/utils/LLVM-9.0.0-rc1-win64/bin/llvm-lib.exe" -DCMAKE_RANLIB="F:/Clangbuilder/bin/utils/LLVM-9.0.0-rc1-win64/bin/llvm-ranlib.exe" I found that this may be related to the fact that clang does not eliminate the constexpr symbol.
Test two files
typea.cc:
#include <cstdio> #include <type_traits> bool typetest2() { int n = 0; return std::is_integral<int>::value; } int main() { /* code */ return 0; } typeb.cc:
#include <type_traits> bool typetest() { int n = 0; return std::is_integral<int>::value; }compile: clang-cl typea.cc typeb.cc -std:c++N
clang-cl 8.0.1 -std:c++14 and -std:c++17 build success, link success
clang-cl 9.0.0 rc1 -std:c++14 build success. link failed: error LNK2005
clang-cl 9.0.0 rc1 -std:c++17 build success. link success.