GHCi下的动态加载

Question

我需要能够动态加载 Haskell 模块，并在动态加载模块的上下文中评估表达式。

Hint 做到了；问题是，至少在 Windows 上，它在 GHCi 下不起作用。

cygwin-bash> ghci HintTest.hs
GHCi, version 7.6.3: http://www.haskell.org/ghc/  :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
Ok, modules loaded: Main.
Prelude Main>
Prelude Main> main
[... lots of "Loading package" messages snipped]

GHCi runtime linker: fatal error: I found a duplicate definition for symbol
   _debugLn
whilst processing object file
   C:\PROGRAM FILES (X86)\HASKELL PLATFORM\2013.2.0.0\lib\ghc-prim-0.3.0.0\HSghc-prim-0.3.0.0.o
This could be caused by:
   * Loading two different object files which export the same symbol
   * Specifying the same object file twice on the GHCi command line
   * An incorrect `package.conf' entry, causing some object to be
     loaded twice.
GHCi cannot safely continue in this situation.  Exiting now.  Sorry.

直接使用 GHC 模块时出现同样的错误，如GHC/As a library 所示。

作为编译程序，HintTest 运行良好。

对此有什么可以做的吗？

我不需要单独运行我的程序；总是使用 GHCi 就足够了。如果程序可以使用 GHCi 本身作为解释器而不是它自己的 GHC 副本，那也很好。也就是说，我希望能够做这样的事情：

do
  context <- loadToGhci "MyModule.hs"
  inContext context "MyModule.myFunction 2 5"

当我返回 REPL 时，MyModule 会神奇地加载到其中。 context 意味着某种带有 GHCi 状态的 monad。

更新 相同的代码适用于 Linux。也许这是 GHC 中特定于 Windows 的错误。可以解决吗？

更新 2 这是完整的日志

Prelude Main> main
Loading package array-0.4.0.1 ... linking ... done.
Loading package deepseq-1.3.0.1 ... linking ... done.
Loading package bytestring-0.10.0.2 ... linking ... done.
Loading package Win32-2.3.0.0 ... linking ... done.
Loading package transformers-0.3.0.0 ... linking ... done.
Loading package old-locale-1.0.0.5 ... linking ... done.
Loading package time-1.4.0.1 ... linking ... done.
Loading package syb-0.4.0 ... linking ... done.
Loading package random-1.0.1.1 ... linking ... done.
Loading package filepath-1.3.0.1 ... linking ... done.
Loading package directory-1.2.0.1 ... linking ... done.
Loading package process-1.1.0.2 ... linking ... done.
Loading package pretty-1.1.1.0 ... linking ... done.
Loading package mtl-2.1.2 ... linking ... done.
Loading package containers-0.5.0.0 ... linking ... done.
Loading package hpc-0.6.0.0 ... linking ... done.
Loading package hoopl-3.9.0.0 ... linking ... done.
Loading package haskell-src-1.0.1.5 ... linking ... done.
Loading package old-time-1.1.0.1 ... linking ... done.
Loading package Cabal-1.16.0 ... linking ... done.
Loading package binary-0.5.1.1 ... linking ... done.
Loading package bin-package-db-0.0.0.0 ... linking ... done.
Loading package template-haskell ... linking ... done.
Loading package ghc-7.6.3 ... linking ... done.
Loading package extensible-exceptions-0.1.1.4 ... linking ... done.
Loading package MonadCatchIO-mtl-0.3.0.5 ... linking ... done.
Loading package ghc-mtl-1.0.1.2 ... linking ... done.
Loading package ghc-paths-0.1.0.9 ... linking ... done.
Loading package utf8-string-0.3.7 ... linking ... done.
Loading package hint-0.3.3.7 ... linking ... done.


GHCi runtime linker: fatal error: I found a duplicate definition for symbol
   _debugLn
whilst processing object file
   C:\PROGRAM FILES (X86)\HASKELL PLATFORM\2013.2.0.0\lib\ghc-prim-0.3.0.0\HSghc-prim-0.3.0.0.o
This could be caused by:
   * Loading two different object files which export the same symbol
   * Specifying the same object file twice on the GHCi command line
   * An incorrect `package.conf' entry, causing some object to be
     loaded twice.
GHCi cannot safely continue in this situation.  Exiting now.  Sorry.

Answer 1

您正在尝试将字节码解释器和运行时动态加载到字节码解释器和运行时中。这是否有效取决于底层 C 库在您的系统上的链接方式——这非常依赖于平台。

特别是，除非在链接时特别小心，否则当您第二次加载各种 RTS 模块时，C 符号将重复，这将导致链接器错误。