CentOS 7 如何安裝llvm-project-10.0.0？

需要先升級gcc至7.5版本，詳見CentOS 7如何編譯安裝升級gcc版本?一文

# 備份之前的yum .repo文件至 /tmp/repo_bak 目錄
mkdir -p /tmp/repo_bak &&  cd /etc/yum.repo.d && /bin/mv ./*.repo /tmp/repo_bak# 更換yum軟件源為阿里云鏡像源，執行腳本后一直全部回車即可
bash <(curl -sSL https://linuxmirrors.cn/main.sh)# 使用阿里云鏡像源安裝編譯依賴
yum install -y gcc gcc-c++ make cmake3 git zlib-devel ncurses-devel# 聲明新GCC相關的環境變量，注意此步必須執行，否則后續GCC編譯無法調用7.5版本新的運行庫
cat << 'EOF' >> ~/.bashrc
export PATH=/usr/local/bin:$PATH
export LD_LIBRARY_PATH=/usr/local/lib64:$LD_LIBRARY_PATH
export LIBRARY_PATH=/usr/local/lib64:$LIBRARY_PATH
export C_INCLUDE_PATH=/usr/local/include
export CPLUS_INCLUDE_PATH=/usr/local/include/c++/7.5.0
EOF
source ~/.bashrc# 驗證系統是否可以加載到 libstdc++.so.6 與 GLIBCXX_3.4.21，若無法加載需升級gcc至7.5版本
ldd $(which g++) ｜ grep libstdc++.so.6 => /usr/local/lib64/libstdc++.so.6
strings /usr/local/lib64/libstdc++.so.6 | grep GLIBCXX_3.4.21cd /tmp
# 下載 LLVM 源碼
wget https://github.com/llvm/llvm-project/releases/download/llvmorg-10.0.0/llvm-project-10.0.0.tar.xz
tar -xf llvm-project-10.0.0.tar.xz# 注意：此處必須創建單獨的構建目錄，必須在非源碼目錄中構建（LLVM 禁止 in-source build）
mkdir -p /tmp/llvm-project-10.0.0/llvm-build
cd /tmp/llvm-project-10.0.0/llvm-build# 運行 cmake3，在 build 目錄中，指向 llvm 源碼目錄
cmake3 -G "Unix Makefiles" \-DCMAKE_C_COMPILER=/usr/local/bin/gcc \-DCMAKE_CXX_COMPILER=/usr/local/bin/g++ \-DCMAKE_BUILD_TYPE=Release \-DCMAKE_INSTALL_PREFIX=/opt/llvm-10 \-DLLVM_ENABLE_PROJECTS="clang" \-DLLVM_TARGETS_TO_BUILD="X86" \-DLLVM_ENABLE_TERMINFO=OFF \../llvm# 編譯并安裝，預計需要3小時左右
make -j1 VERBOSE=1
sudo make install# 編譯完成后驗證 llvm-config
/opt/llvm-10/bin/llvm-config --version# 聲明 LLVM-10 工具鏈 環境變量
cat << 'EOF' >> ~/.bashrc
export PATH=/opt/llvm-10/bin:$PATH
export LD_LIBRARY_PATH=/opt/llvm-10/lib:$LD_LIBRARY_PATH
EOF
source ~/.bashrc# 驗證LLVM-10 工具鏈是否可以正常使用
clang --version
llvm-config --prefix

筆者安裝踩坑過程：
1 執行cmake3 -G "Unix Makefiles" -DCMAKE_INSTALL_PREFIX=/opt/llvm-10 ../輸出ERROR：

CMake Error: The source directory “/tmp/llvm-project-10.0.0” does not appear to contain CMakeLists.txt.
Specify --help for usage, or press the help button on the CMake GUI.

解決方案：cmake3構建要明確指定包含CMake構建系統核心配置文件的目錄位置

llvm-project-10.0.0/
├── llvm  ? <- 需要在cmake3構建命令結尾明確指定這個目錄尋找CMake構建系統的核心配置文件
│   ├── CMakeLists.txt  
│   └── ...
├── clang/
├── lld/
└── ...

改為為如下命令

cd /tmp
# 下載 LLVM 源碼
wget https://github.com/llvm/llvm-project/releases/download/llvmorg-10.0.0/llvm-project-10.0.0.tar.xz
tar -xf llvm-project-10.0.0.tar.xz# 注意：此處必須創建單獨的構建目錄，必須在非源碼目錄中構建（LLVM 禁止 in-source build）
mkdir -p /tmp/llvm-project-10.0.0/llvm-build
cd /tmp/llvm-project-10.0.0/llvm-buildcmake3 -G "Unix Makefiles" \-DCMAKE_C_COMPILER=/usr/local/bin/gcc \-DCMAKE_CXX_COMPILER=/usr/local/bin/g++ \-DCMAKE_BUILD_TYPE=Release \-DCMAKE_INSTALL_PREFIX=/opt/llvm-10 \-DLLVM_ENABLE_PROJECTS="clang" \-DLLVM_TARGETS_TO_BUILD="X86" \-DLLVM_ENABLE_TERMINFO=OFF \../llvm #  ? <- 明確指定llvm目錄，用于尋找CMake構建系統的核心配置文件

2 在/tmp/llvm-project-10.0.0/lllvm目錄下cmake3 構建輸出ERROR：

CMake Error at CMakeLists.txt:242 (message):
In-source builds are not allowed.

Please create a directory and run cmake from there, passing the path

to this source directory as the last argument.

This process created the file CMakeCache.txt’ and the directory
CMakeFiles’.

Please delete them.

– Configuring incomplete, errors occurred!
See also “/tmp/llvm-project-10.0.0/llvm/CMakeFiles/CMakeOutput.log”.

解決方案：LLVM 明確要求在單獨的 build 目錄中構建，禁止在源代碼目錄 llvm-project-10.0.0/llvm 中運行了 cmake3

3 執行make -j$(nproc)輸出ERROR：

CMake Error at cmake/modules/CheckCompilerVersion.cmake:38 (message):
Host GCC version must be at least 5.1, your version is 4.8.5.
Call Stack (most recent call first):
cmake/modules/CheckCompilerVersion.cmake:48 (check_compiler_version)
cmake/config-ix.cmake:13 (include)
CMakeLists.txt:623 (include)

– Configuring incomplete, errors occurred!
See also “/tmp/llvm-project-10.0.0/build/CMakeFiles/CMakeOutput.log”.

解決方案：編譯要求 GCC ≥ 5.1，但CentOS 7系統默認是 4.8.5，升級系統GCC版本至7.5，詳見CentOS 7如何編譯安裝升級gcc版本?一文

4 執行make -j$(nproc)輸出ERROR：
…/…/…/bin/llvm-tblgen: /lib64/libstdc++.so.6: version GLIBCXX_3.4.20’ not found (required by …/…/…/bin/llvm-tblgen)
…/…/…/bin/llvm-tblgen: /lib64/libstdc++.so.6: version CXXABI_1.3.9’ not found (required by …/…/…/bin/llvm-tblgen)
…/…/…/bin/llvm-tblgen: /lib64/libstdc++.so.6: version GLIBCXX_3.4.21’ not found (required by …/…/…/bin/llvm-tblgen)
make[2]: *** [include/llvm/IR/Attributes.inc] Error 1
make[2]: Leaving directory /home/tmp/llvm-project-10.0.0/llvm-build’
make[1]: *** [include/llvm/IR/CMakeFiles/intrinsics_gen.dir/all] Error 2
make[1]: Leaving directory /home/tmp/llvm-project-10.0.0/llvm-build’
make: *** [all] Error 2
解決方案：先聲明環如下境變量，再將make -j$(nproc)并行編譯改為make -j1 VERBOSE=1

# 聲明新GCC相關的環境變量，注意此步必須執行，否則后續GCC編譯無法調用7.5版本新的運行庫
cat << 'EOF' >> ~/.bashrc
export PATH=/usr/local/bin:$PATH
export LD_LIBRARY_PATH=/usr/local/lib64:$LD_LIBRARY_PATH
export LIBRARY_PATH=/usr/local/lib64:$LIBRARY_PATH
export C_INCLUDE_PATH=/usr/local/include
export CPLUS_INCLUDE_PATH=/usr/local/include/c++/7.5.0
EOF
source ~/.bashrc

5 執行clang --version與 llvm-config --prefix輸出ERROR：

clang: /lib64/libstdc++.so.6: version GLIBCXX_3.4.22 not found (required by clang) clang: /lib64/libstdc++.so.6: version GLIBCXX_3.4.20 not found (required by clang)
clang: /lib64/libstdc++.so.6: version GLIBCXX_3.4.21 not found (required by clang) clang: /lib64/libstdc++.so.6: version CXXABI_1.3.9 not found (required by clang)
llvm-config: /lib64/libstdc++.so.6: version CXXABI_1.3.9 not found (required by llvm-config) llvm-config: /lib64/libstdc++.so.6: version GLIBCXX_3.4.21 not found (required by llvm-config)

解決方案：聲明新GCC相關的環境變量使動態鏈接器可以加載到新GCC的 libstdc++庫

# 聲明新GCC相關的環境變量，注意此步必須執行，否則后續GCC編譯無法調用7.5版本新的運行庫
cat << 'EOF' >> ~/.bashrc
export PATH=/usr/local/bin:$PATH
export LD_LIBRARY_PATH=/usr/local/lib64:$LD_LIBRARY_PATH
export LIBRARY_PATH=/usr/local/lib64:$LIBRARY_PATH
export C_INCLUDE_PATH=/usr/local/include
export CPLUS_INCLUDE_PATH=/usr/local/include/c++/7.5.0
EOF
source ~/.bashrc