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Windows中使用GHCI的Haskell外部函数接口(Haskell Foreign Function Interface with GHCI in Windows)

 首先，我指定使用Windows 10 64位和Haskell Platform 8.0.1。  
 我尝试使用以下代码在Windows中使用Haskell的FFI。  
import Control.Monad
import Data.Char
import Foreign.C

getCh :: IO Char
getCh = liftM (chr . fromEnum) c_getch
foreign import ccall unsafe "conio.h getch" c_getch :: IO CInt

main :: IO ()
main = getCh >>= \x -> print x
 
 在此之后，我可以用ghc编译好  
> ghc Examples.hs
[1 of 1] Compiling Main             ( Examples.hs, Examples.o )
Linking Examples.exe ...
 
 它完全运行。  
> Examples.exe
'1'
 
 （运行后输入1时）  
 但是，GHCI会出现问题。 当我把它加载到ghci时，我收到了这些消息。  
> ghci Examples.hs
GHCi, version 8.0.1: http://www.haskell.org/ghc/  :? for help
[1 of 1] Compiling Main             ( Examples.hs, interpreted )
Ok, modules loaded: Main.
*Main> main

ByteCodeLink: can't find label
During interactive linking, GHCi couldn't find the following symbol:
  getch
This may be due to you not asking GHCi to load extra object files,
archives or DLLs needed by your current session.  Restart GHCi, specifying
the missing library using the -L/path/to/object/dir and -lmissinglibname
flags, or simply by naming the relevant files on the GHCi command line.
Alternatively, this link failure might indicate a bug in GHCi.
If you suspect the latter, please send a bug report to:
  glasgow-haskell-bugs@haskell.org

*Main>
 
 我尝试加载“缺少库”，例如需要使用conio.h “ -lmsvcrt ”，但结果是悲观相同的。  
> ghci -lmsvcrt Examples.hs
GHCi, version 8.0.1: http://www.haskell.org/ghc/  :? for help
[1 of 1] Compiling Main             ( Examples.hs, interpreted )
Ok, modules loaded: Main.
*Main> main

ByteCodeLink: can't find label
During interactive linking, GHCi couldn't find the following symbol:
  getch
This may be due to you not asking GHCi to load extra object files,
archives or DLLs needed by your current session.  Restart GHCi, specifying
the missing library using the -L/path/to/object/dir and -lmissinglibname
flags, or simply by naming the relevant files on the GHCi command line.
Alternatively, this link failure might indicate a bug in GHCi.
If you suspect the latter, please send a bug report to:
  glasgow-haskell-bugs@haskell.org

*Main>
 
 GHCI可能会加载库，因为当我尝试加载错误的库时，ghci会输出错误。  
 我尝试了几个其他的东西，比如使用ghci Examples.hs -fobject-code ， ghci -lmsvcrt Examples.hs -fobject-code ，甚至  
ghci Examples.hs "-luser32" "-lgdi32" "-lwinmm" "-ladvapi32" "-lshell32"
"-lshfolder" "-lwsock32" "-luser32" "-lshell32" "-lmsvcrt" "-lmingw32" 
"-lmingwex" "-luser32" "-lmingw32" "-lmingwex" "-lm" "-lwsock32" "-lgdi32" "-lwinmm"
 
 这在ghc Examples.hs -v5找到。  
 可悲的是，没有什么比我的main更有用了，我找不到任何其他方法。  
 PS有没有人知道如何在Windows中使用hSetBuffering（它是在8年前发布的ghc票＃2189 。是不是已修复？） 

First of all, I specify that I use Windows 10 64bit and Haskell Platform 8.0.1. 
I try to use FFI of Haskell in Windows using following code. 
import Control.Monad
import Data.Char
import Foreign.C

getCh :: IO Char
getCh = liftM (chr . fromEnum) c_getch
foreign import ccall unsafe "conio.h getch" c_getch :: IO CInt

main :: IO ()
main = getCh >>= \x -> print x
 
After this, I can compile this well with ghc 
> ghc Examples.hs
[1 of 1] Compiling Main             ( Examples.hs, Examples.o )
Linking Examples.exe ...
 
and it runs completely. 
> Examples.exe
'1'
 
(When I type 1 after running it) 
However, the problem occurs with GHCI. When I load it to ghci, I got these messages. 
> ghci Examples.hs
GHCi, version 8.0.1: http://www.haskell.org/ghc/  :? for help
[1 of 1] Compiling Main             ( Examples.hs, interpreted )
Ok, modules loaded: Main.
*Main> main

ByteCodeLink: can't find label
During interactive linking, GHCi couldn't find the following symbol:
  getch
This may be due to you not asking GHCi to load extra object files,
archives or DLLs needed by your current session.  Restart GHCi, specifying
the missing library using the -L/path/to/object/dir and -lmissinglibname
flags, or simply by naming the relevant files on the GHCi command line.
Alternatively, this link failure might indicate a bug in GHCi.
If you suspect the latter, please send a bug report to:
  glasgow-haskell-bugs@haskell.org

*Main>
 
I try to load "missing library", such as "-lmsvcrt" which needs to use conio.h, but result is pessimistically same. 
> ghci -lmsvcrt Examples.hs
GHCi, version 8.0.1: http://www.haskell.org/ghc/  :? for help
[1 of 1] Compiling Main             ( Examples.hs, interpreted )
Ok, modules loaded: Main.
*Main> main

ByteCodeLink: can't find label
During interactive linking, GHCi couldn't find the following symbol:
  getch
This may be due to you not asking GHCi to load extra object files,
archives or DLLs needed by your current session.  Restart GHCi, specifying
the missing library using the -L/path/to/object/dir and -lmissinglibname
flags, or simply by naming the relevant files on the GHCi command line.
Alternatively, this link failure might indicate a bug in GHCi.
If you suspect the latter, please send a bug report to:
  glasgow-haskell-bugs@haskell.org

*Main>
 
GHCI probably loads the library, since when I try to load a wrong library, ghci prints errors about that. 
I try several other things, like using ghci Examples.hs -fobject-code, ghci -lmsvcrt Examples.hs -fobject-code, and even 
ghci Examples.hs "-luser32" "-lgdi32" "-lwinmm" "-ladvapi32" "-lshell32"
"-lshfolder" "-lwsock32" "-luser32" "-lshell32" "-lmsvcrt" "-lmingw32" 
"-lmingwex" "-luser32" "-lmingw32" "-lmingwex" "-lm" "-lwsock32" "-lgdi32" "-lwinmm"
 
Which was found in ghc Examples.hs -v5. 
Sadly, Nothing works for my main, and I can't find any otherway for this. 
P.S. Is there anyone knowing how to use hSetBuffering in Windows (It was posted at 8 years ago in ghc ticket #2189. Isn't it fixed?)

原文：https://stackoverflow.com/questions/38282624

更新时间：2021-04-15 17:04

最满意答案

 在开发过程中删除“On Error GoTo”以更容易地看到有错误的行。  
 在处理所有子文件夹之前，您无需关注当前错误。  
 尝试这个：  
Private Sub LoopFolders_Test()

    'Application Variables
    Dim olApp As Outlook.Application
    Dim objNS As Outlook.Namespace
    Dim myolItems As Folder

    Dim Start As Date
    Dim EndTime As Date

    Set olApp = Outlook.Application
    Set objNS = olApp.GetNamespace("MAPI")
    'Set myOlItems = objNS.GetDefaultFolder(olFolderInbox)
    Set myolItems = objNS.PickFolder

    If myolItems Is Nothing Then GoTo exitRoutine

    Start = Now
    Debug.Print "Start: " & Start
    Debug.Print "Startfolder Name: " & myolItems.Name

    'Disable Screen Updating
    'Application.ScreenUpdating = False

    LoopFolders myolItems.Folders

    ' Finalize Excel display here

exitRoutine:
    Set olApp = Nothing
    Set objNS = Nothing
    Set myolItems = Nothing  

    'Enable Screen Updating
    'Application.ScreenUpdating = True

    EndTime = Now
    Debug.Print "End  : " & EndTime
    Debug.Print Format((EndTime - Start) * 86400, "#,##0.0") & " seconds"

End Sub

Private Sub LoopFolders(olFolders As Folders)

  Dim F As Folder

  For Each F In olFolders
    DoEvents    
    Debug.Print "Subfolder Name: " & F.Name ' Code has not crashed
    ' Count mail here
    LoopFolders F.Folders
  Next

End Sub

While in development remove "On Error GoTo" to more easily see the lines with errors. 
You need not focus on the current errors until you can process all the subfolders. 
Try this: 
Private Sub LoopFolders_Test()

    'Application Variables
    Dim olApp As Outlook.Application
    Dim objNS As Outlook.Namespace
    Dim myolItems As Folder

    Dim Start As Date
    Dim EndTime As Date

    Set olApp = Outlook.Application
    Set objNS = olApp.GetNamespace("MAPI")
    'Set myOlItems = objNS.GetDefaultFolder(olFolderInbox)
    Set myolItems = objNS.PickFolder

    If myolItems Is Nothing Then GoTo exitRoutine

    Start = Now
    Debug.Print "Start: " & Start
    Debug.Print "Startfolder Name: " & myolItems.Name

    'Disable Screen Updating
    'Application.ScreenUpdating = False

    LoopFolders myolItems.Folders

    ' Finalize Excel display here

exitRoutine:
    Set olApp = Nothing
    Set objNS = Nothing
    Set myolItems = Nothing  

    'Enable Screen Updating
    'Application.ScreenUpdating = True

    EndTime = Now
    Debug.Print "End  : " & EndTime
    Debug.Print Format((EndTime - Start) * 86400, "#,##0.0") & " seconds"

End Sub

Private Sub LoopFolders(olFolders As Folders)

  Dim F As Folder

  For Each F In olFolders
    DoEvents    
    Debug.Print "Subfolder Name: " & F.Name ' Code has not crashed
    ' Count mail here
    LoopFolders F.Folders
  Next

End Sub

Windows中使用GHCI的Haskell外部函数接口(Haskell Foreign Function Interface with GHCI in Windows)

最满意答案

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