Executables fail on windows if the executable name has a dot in it

[j3h]

If an executable name has a dot in it, it is not generated with an .exe extension on Windows. It works fine under Linux. See the attached example to reproduce.

$ cabal --version
cabal-install version 0.8.2
using version 1.8.0.6 of the Cabal library 


$ cabal install
Resolving dependencies...
Configuring bad-exe-0.1...
Preprocessing executables for bad-exe-0.1...
Building bad-exe-0.1...
[1 of 1] Compiling Main             ( Main.hs, dist\build\bad.name\bad.name-tmp\Main.o )

Main.hs:1:0:
    Warning: Module `Prelude' is deprecated:
               You are using the old package `base' version 3.x.
               Future GHC versions will not support base version 3.x. You
               should update your code to use the new base version 4.x.
Linking dist\build\bad.name\bad.name ...
Installing executable(s) in C:\Users\hudson\AppData\Roaming\cabal\bin
cabal.exe: dist\build\bad.name\bad.name.exe: does not exist
cabal.exe: Error: some packages failed to install:
bad-exe-0.1 failed during the final install step. The exception was:
ExitFailure 1

[j3h]

A trivial package with a dot in the exe file name

[duncan]

Currently the code does:

  -- exeNameReal, the name that GHC really uses (with .exe on Windows)
  let exeNameReal = exeName' <.>
                    (if null $ takeExtension exeName' then exeExtension else "")

Where as I would expect it should be simply

  -- exeNameReal, the name that GHC really uses (with .exe on Windows)
  let exeNameReal = exeName' <.> exeExtension

since p <.> "" = p.

It is not clear to me why the code is like it is now. The code was added by the patch

Mon Aug 21 15:30:21 BST 2006  Neil Mitchell
  * Make -o use the filename as GHC will, i.e. with .exe on the end for Windows.
 This fixes a GHC 6.4.2 bug with relinking every time.

the code was

  -- exeNameReal, the name that GHC really uses (with .exe on Windows)
  let exeNameReal = exeName' `joinFileExt`
                    (if null $ snd $ splitFileExt exeName' then exeExtension else "")

Previously it had relied on ghc adding the .exe extension. It is still not obvious why it is coded the way it is, if it's an oversight or something I'm missing. In principle the above allows people to make an executable that does not use the .exe extension.