"libstdc++ version must be at least" assertion when building with libc++

[DenisYaroshevskiy]

Hi!

I

1. cloned/built/installed llvm
2. rebuilding llvm with the latest llvm trunk.

First time it worked, but when I am building with trunk, the configuration fails.

Please help?

history of commands

 2017  CC=clang CXX=clang++ cmake -G Ninja -DCMAKE_CXX_FLAGS="--stdlib=libc++ -march=native" -DLLVM_ENABLE_RUNTIMES=all -DLLVM_ENABLE_PROJECTS="clang;clang-tools-extra;cross-project-tests;libc;libclc;lld;lldb;openmp;polly;pstl" -DCMAKE_BUILD_TYPE=Release  ../llvm
 2018  clear
 2019  time ninja
 2020  sudo ninja install
 2021  rm -rf *
 2022  CC=clang CXX=clang++ cmake -G Ninja -DCMAKE_CXX_FLAGS="--stdlib=libc++ -march=native" -DLLVM_ENABLE_RUNTIMES=all -DLLVM_ENABLE_PROJECTS="clang;clang-tools-extra;cross-project-tests;libc;libclc;lld;lldb;openmp;polly;pstl" -DCMAKE_BUILD_TYPE=Release  ../llvm

Now fails with

CMake Error at cmake/modules/CheckCompilerVersion.cmake:88 (message):
  libstdc++ version must be at least 7.4.
Call Stack (most recent call first):
  cmake/config-ix.cmake:16 (include)
  CMakeLists.txt:872 (include)

Versions:

clang --version
clang version 18.0.0 (git@github.com:llvm/llvm-project.git 444abb396c340e52a8a4db5778b7d6b3b6195070)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/bin

clang++ --version
clang version 18.0.0 (git@github.com:llvm/llvm-project.git 444abb396c340e52a8a4db5778b7d6b3b6195070)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/bin

[DenisYaroshevskiy]

UPD: this was this issue: https://discourse.llvm.org/t/string-is-not-a-directory/63426

After building with stock gcc and trying to install things I get

-- Up-to-date: /usr/local/include/c++/v1/__stop_token/stop_token.h
CMake Error at cmake_install.cmake:2666 (file):
  file INSTALL destination: /usr/local/include/c++/v1/__string is not a
  directory.
Call Stack (most recent call first):
  /home/dyarosh/space/llvm-project/build/runtimes/runtimes-bins/libcxx/cmake_install.cmake:47 (include)
  /home/dyarosh/space/llvm-project/build/runtimes/runtimes-bins/cmake_install.cmake:57 (include)


ninja: build stopped: subcommand failed.
FAILED: runtimes/CMakeFiles/install-cxx /home/dyarosh/space/llvm-project/build/runtimes/CMakeFiles/install-cxx 
cd /home/dyarosh/space/llvm-project/build/runtimes/runtimes-bins && /snap/cmake/1329/bin/cmake --build /home/dyarosh/space/llvm-project/build/runtimes/runtimes-bins/ --target install-cxx --config Release
ninja: build stopped: subcommand failed.

This is the command I run sudo ninja install-cxx install-cxxabi install-unwind

How I build:

CC=gcc CXX=g++ cmake -G Ninja -DCMAKE_CXX_FLAGS="-march=native" -DLLVM_ENABLE_RUNTIMES=all -DLLVM_ENABLE_PROJECTS="clang;clang-tools-extra;;lld;lldb;openmp;polly;pstl" -DCMAKE_BUILD_TYPE=Release  ../llvm

time ninja

[philnik777]

You probably just want to use LLVM_ENABLE_LIBCXX.

[DenisYaroshevskiy]

You probably just want to use LLVM_ENABLE_LIBCXX.

I don't think I do, do I?. According to this https://llvm.org/docs/CMake.html it just changes default to --stdlib=libc++ on invocations.

But I think I almost got it working with that last attempt. I will close the issue once I'm sure

[ldionne]

I think you are overwriting an existing (but older) installation of libc++. There used to be a file named __string and now it's a directory, and I think CMake is complaining that you're trying to replace the old file with the new directory when you install.

IMO this is not something we should try to "fix" on the project side. Tentatively closing to keep things tidy but please reopen in case there is further discussion.

[DenisYaroshevskiy]

Yes that was exactly right