“the之痛”的来源在哪里？

Question

我正在运行stack版本1.1.2 x86_64 hpack-0.14.1

$ stack exec which ghc
Run from outside a project, using implicit global project config
Using resolver: lts-5.10 from implicit global project's config file: /home/wisut/.stack/global-project/stack.yaml
/home/wisut/.stack/programs/x86_64-linux/ghc-7.10.3/bin/ghc

但是，当使用stack ghci和GHC.Paths时，返回错误的路径。

$ stack ghci
Run from outside a project, using implicit global project config
Using resolver: lts-5.10 from implicit global project's config file: /home/wisut/.stack/global-project/stack.yaml
Error parsing targets: The specified targets matched no packages. Perhaps you need to run 'stack init'?
Warning: build failed, but optimistically launching GHCi anyway
Configuring GHCi with the following packages: 
GHCi, version 7.10.3: http://www.haskell.org/ghc/  :? for help
Ok, modules loaded: none.
Prelude> GHC.Paths.ghc
"/usr/bin/ghc-7.10.3"

我运行的是带有GHC8.0.1的Arch，因为在stack之外没有ghc-7。

[wisut@earth ~]$ which ghc
/usr/bin/ghc
[wisut@earth ~]$ ghc --version
The Glorious Glasgow Haskell Compilation System, version 8.0.1
[wisut@earth ~]$ ls -al /usr/bin/ghc
lrwxrwxrwx 1 root root 9 May 24 18:28 /usr/bin/ghc -> ghc-8.0.1

查看GHC.Paths源代码，我不知道值来自何处。是ENV车吗？

{-# LANGUAGE CPP #-}

module GHC.Paths (
        ghc, ghc_pkg, libdir, docdir
  ) where

libdir, docdir, ghc, ghc_pkg :: FilePath

libdir  = GHC_PATHS_LIBDIR
docdir  = GHC_PATHS_DOCDIR

ghc     = GHC_PATHS_GHC
ghc_pkg = GHC_PATHS_GHC_PKG

运行stack exec env没有看到任何东西。

$ stack exec env | grep -i ghc
Run from outside a project, using implicit global project config
GHC_PACKAGE_PATH=/home/wisut/.stack/global-project/.stack-work/installx86_64-linux/lts-5.10/7.10.3/pkgdb:/home/wisut/.stack/snapshots/x86_64-linux/lts-5.10/7.10.3/pkgdb:/home/wisut/.stack/programs/x86_64-linux/ghc-7.10.3/lib/ghc-7.10.3/package.conf.d
PATH=/home/wisut/.stack/global-project/.stack-work/install/x86_64-linux/lts-5.10/7.10.3/bin:/home/wisut/.stack/snapshots/x86_64-linux/lts-5.10/7.10.3/bin:/home/wisut/.stack/programs/x86_64-linux/ghc-7.10.3/bin:/home/wisut/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/bin:/usr/lib/jvm/default/bin:/usr/bin/site_perl:/usr/bin/vendor_perl:/usr/bin/core_perl

我怎样才能修正错误的值？如何配置stack使GHC.Paths返回正确的？

UPD我试着用--no-system-ghc运行stack，但没有什么区别。我试图删除我的~/.cabal和~/.stack文件夹。我不得不执行stack setup，在stack重新安装编译器之后，它不会给出错误的路径，但是它不会给我任何路径，该命令的输出现在是空的。我在Setup.hs中也没有什么特别之处。

Answer 1

您几乎是对的，GHC_变量是来自Setup.hs的CPP定义。

let buildinfo = emptyBuildInfo{
         cppOptions = ["-DGHC_PATHS_GHC_PKG=" ++ show c_ghc_pkg,
                       "-DGHC_PATHS_GHC=" ++ show c_ghc,
                       "-DGHC_PATHS_LIBDIR=" ++ show libdir,
                       "-DGHC_PATHS_DOCDIR=" ++ show docdir ]
       }

关于您的错误路径问题，请尝试运行stack --no-system-ghc ghci。如果它仍然为GHC路径显示"/usr/bin/ghc-7.10.3"，那么当您为GHC-7.10.3编译ghc-paths时，我怀疑在那里有 GHC，而且由于stack在不重建东西方面很好，所以旧版本的ghc-paths仍然存在。我不知道如何在快照中重新构建包，然后重新启动~/.stack；这可能是个好主意。如果你改变了你的全球GHC计划。

有一个相关的问题：停止使用系统-ghc。