通过 Homebrew 安装 ccls 会输出与 libffi 和 llvm 相关的警告消息
Installing ccls through Homebrew outputs caveats messages related to libffi and llvm
我正在尝试设置我的 neovim C++ 开发环境，并想使用 ccls 作为我的 coc 语言服务器。
当我使用 Homebrew 安装 ccls 时，它会安装 libffi 和 llvm 作为依赖项。
好像 ccls 安装成功了，但是好像我需要配置 PATH 变量，LDFLAGS 和 CPPFLAGS.
但是我不知道libffi和llvm是干什么用的，他们提示的LDFLAGS和CPPFLAGS不一样，很迷惑。
可以不导出任何变量来使用ccls吗？或者，我应该在 ~/.zshrc 中导出哪个版本？
下面是 brew install ccls 的控制台输出。
❯ brew install ccls
==> Downloading https://homebrew.bintray.com/bottles/libffi-3.3.big_sur.bottle.tar.gz
######################################################################## 100.0%
==> Downloading https://homebrew.bintray.com/bottles/llvm-11.0.0_1.big_sur.bottle.tar.gz
==> Downloading from https://d29vzk4ow07wi7.cloudfront.net/c8e30903a9a4f695780e1eeeaa2cf4d5a95141a1cac98ab1bbc811817cde39ca?response-content-disposition=attachment%3Bfilename%3D
######################################################################## 100.0%
==> Downloading https://homebrew.bintray.com/bottles/ccls-0.20201219.big_sur.bottle.tar.gz
==> Downloading from https://d29vzk4ow07wi7.cloudfront.net/934fb8fd594d6e7adbfa14b5608f1de14309db34f2cf61a0cb572bdc772b2aa3?response-content-disposition=attachment%3Bfilename%3D
######################################################################## 100.0%
==> Installing dependencies for ccls: libffi and llvm
==> Installing ccls dependency: libffi
==> Pouring libffi-3.3.big_sur.bottle.tar.gz
==> Caveats
libffi is keg-only, which means it was not symlinked into /usr/local,
because macOS already provides this software and installing another version in
parallel can cause all kinds of trouble.
For compilers to find libffi you may need to set:
export LDFLAGS="-L/usr/local/opt/libffi/lib"
export CPPFLAGS="-I/usr/local/opt/libffi/include"
==> Summary
/usr/local/Cellar/libffi/3.3: 17 files, 540.2KB
==> Installing ccls dependency: llvm
==> Pouring llvm-11.0.0_1.big_sur.bottle.tar.gz
==> Caveats
To use the bundled libc++ please add the following LDFLAGS:
LDFLAGS="-L/usr/local/opt/llvm/lib -Wl,-rpath,/usr/local/opt/llvm/lib"
llvm is keg-only, which means it was not symlinked into /usr/local,
because macOS already provides this software and installing another version in
parallel can cause all kinds of trouble.
If you need to have llvm first in your PATH run:
echo 'export PATH="/usr/local/opt/llvm/bin:$PATH"' >> ~/.zshrc
For compilers to find llvm you may need to set:
export LDFLAGS="-L/usr/local/opt/llvm/lib"
export CPPFLAGS="-I/usr/local/opt/llvm/include"
==> Summary
/usr/local/Cellar/llvm/11.0.0_1: 8,922 files, 1.4GB
==> Installing ccls
==> Pouring ccls-0.20201219.big_sur.bottle.tar.gz
/usr/local/Cellar/ccls/0.20201219: 5 files, 1.5MB
==> Caveats
==> libffi
libffi is keg-only, which means it was not symlinked into /usr/local,
because macOS already provides this software and installing another version in
parallel can cause all kinds of trouble.
For compilers to find libffi you may need to set:
export LDFLAGS="-L/usr/local/opt/libffi/lib"
export CPPFLAGS="-I/usr/local/opt/libffi/include"
==> llvm
To use the bundled libc++ please add the following LDFLAGS:
LDFLAGS="-L/usr/local/opt/llvm/lib -Wl,-rpath,/usr/local/opt/llvm/lib"
llvm is keg-only, which means it was not symlinked into /usr/local,
because macOS already provides this software and installing another version in
parallel can cause all kinds of trouble.
If you need to have llvm first in your PATH run:
echo 'export PATH="/usr/local/opt/llvm/bin:$PATH"' >> ~/.zshrc
For compilers to find llvm you may need to set:
export LDFLAGS="-L/usr/local/opt/llvm/lib"
export CPPFLAGS="-I/usr/local/opt/llvm/include"
libffi 只是一个图书馆。 llvm 是一个 编译器基础结构 。
而libc++是LLVM项目的C++标准库。您可以使用 LLVM 库或 GNU (libstdc++) 库。这取决于您的软件项目（或您的个人喜好）您使用什么库。
由于 macOS 确实已经提供了 llvm 安装，您可以 可选 切换到 brew 作为依赖安装的安装 –这不是必需的。
LDFLAGS 环境变量确实包含编译器（gcc/g++ 或 clang/clang++）传递给链接器的附加标志，即添加链接器可以找到的路径然后，如果 required/used，库对象文件将链接到您的二进制文件。
和CPPFLAGS做同样的事情，但这次标志直接针对编译器，即为库的头文件添加一个额外的搜索路径。
在您的情况下，您不必从 .zshrc 中导出任何（额外的）变量，ccls 无需定义这些变量即可正常工作。
我正在尝试设置我的 neovim C++ 开发环境，并想使用 ccls 作为我的 coc 语言服务器。
当我使用 Homebrew 安装 ccls 时，它会安装 libffi 和 llvm 作为依赖项。
好像 ccls 安装成功了，但是好像我需要配置 PATH 变量，LDFLAGS 和 CPPFLAGS.
但是我不知道libffi和llvm是干什么用的，他们提示的LDFLAGS和CPPFLAGS不一样，很迷惑。
可以不导出任何变量来使用ccls吗？或者，我应该在 ~/.zshrc 中导出哪个版本？
下面是 brew install ccls 的控制台输出。
❯ brew install ccls
==> Downloading https://homebrew.bintray.com/bottles/libffi-3.3.big_sur.bottle.tar.gz
######################################################################## 100.0%
==> Downloading https://homebrew.bintray.com/bottles/llvm-11.0.0_1.big_sur.bottle.tar.gz
==> Downloading from https://d29vzk4ow07wi7.cloudfront.net/c8e30903a9a4f695780e1eeeaa2cf4d5a95141a1cac98ab1bbc811817cde39ca?response-content-disposition=attachment%3Bfilename%3D
######################################################################## 100.0%
==> Downloading https://homebrew.bintray.com/bottles/ccls-0.20201219.big_sur.bottle.tar.gz
==> Downloading from https://d29vzk4ow07wi7.cloudfront.net/934fb8fd594d6e7adbfa14b5608f1de14309db34f2cf61a0cb572bdc772b2aa3?response-content-disposition=attachment%3Bfilename%3D
######################################################################## 100.0%
==> Installing dependencies for ccls: libffi and llvm
==> Installing ccls dependency: libffi
==> Pouring libffi-3.3.big_sur.bottle.tar.gz
==> Caveats
libffi is keg-only, which means it was not symlinked into /usr/local,
because macOS already provides this software and installing another version in
parallel can cause all kinds of trouble.
For compilers to find libffi you may need to set:
export LDFLAGS="-L/usr/local/opt/libffi/lib"
export CPPFLAGS="-I/usr/local/opt/libffi/include"
==> Summary
/usr/local/Cellar/libffi/3.3: 17 files, 540.2KB
==> Installing ccls dependency: llvm
==> Pouring llvm-11.0.0_1.big_sur.bottle.tar.gz
==> Caveats
To use the bundled libc++ please add the following LDFLAGS:
LDFLAGS="-L/usr/local/opt/llvm/lib -Wl,-rpath,/usr/local/opt/llvm/lib"
llvm is keg-only, which means it was not symlinked into /usr/local,
because macOS already provides this software and installing another version in
parallel can cause all kinds of trouble.
If you need to have llvm first in your PATH run:
echo 'export PATH="/usr/local/opt/llvm/bin:$PATH"' >> ~/.zshrc
For compilers to find llvm you may need to set:
export LDFLAGS="-L/usr/local/opt/llvm/lib"
export CPPFLAGS="-I/usr/local/opt/llvm/include"
==> Summary
/usr/local/Cellar/llvm/11.0.0_1: 8,922 files, 1.4GB
==> Installing ccls
==> Pouring ccls-0.20201219.big_sur.bottle.tar.gz
/usr/local/Cellar/ccls/0.20201219: 5 files, 1.5MB
==> Caveats
==> libffi
libffi is keg-only, which means it was not symlinked into /usr/local,
because macOS already provides this software and installing another version in
parallel can cause all kinds of trouble.
For compilers to find libffi you may need to set:
export LDFLAGS="-L/usr/local/opt/libffi/lib"
export CPPFLAGS="-I/usr/local/opt/libffi/include"
==> llvm
To use the bundled libc++ please add the following LDFLAGS:
LDFLAGS="-L/usr/local/opt/llvm/lib -Wl,-rpath,/usr/local/opt/llvm/lib"
llvm is keg-only, which means it was not symlinked into /usr/local,
because macOS already provides this software and installing another version in
parallel can cause all kinds of trouble.
If you need to have llvm first in your PATH run:
echo 'export PATH="/usr/local/opt/llvm/bin:$PATH"' >> ~/.zshrc
For compilers to find llvm you may need to set:
export LDFLAGS="-L/usr/local/opt/llvm/lib"
export CPPFLAGS="-I/usr/local/opt/llvm/include"
libffi 只是一个图书馆。 llvm 是一个 编译器基础结构 。
而libc++是LLVM项目的C++标准库。您可以使用 LLVM 库或 GNU (libstdc++) 库。这取决于您的软件项目（或您的个人喜好）您使用什么库。
由于 macOS 确实已经提供了 llvm 安装，您可以 可选 切换到 brew 作为依赖安装的安装 –这不是必需的。
LDFLAGS 环境变量确实包含编译器（gcc/g++ 或 clang/clang++）传递给链接器的附加标志，即添加链接器可以找到的路径然后，如果 required/used，库对象文件将链接到您的二进制文件。
和CPPFLAGS做同样的事情，但这次标志直接针对编译器，即为库的头文件添加一个额外的搜索路径。
在您的情况下，您不必从 .zshrc 中导出任何（额外的）变量，ccls 无需定义这些变量即可正常工作。