1 <?xml version="1.0" encoding="iso-8859-1"?>
3 <title>Running GHC on Win32 systems</title>
5 <sect1 id="ghc-windows">
7 Starting GHC on Windows platforms</title>
10 The installer that installs GHC on Win32 also sets up the file-suffix associations
11 for ".hs" and ".lhs" files so that double-clicking them starts <command>ghci</command>.
14 Be aware of that <command>ghc</command> and <command>ghci</command> do
15 require filenames containing spaces to be escaped using quotes:
17 c:\ghc\bin\ghci "c:\\Program Files\\Haskell\\Project.hs"
19 If the quotes are left off in the above command, <command>ghci</command> will
20 interpret the filename as two, "c:\\Program" and "Files\\Haskell\\Project.hs".
23 <!-- not clear whether there are current editions of Win32 OSes that
24 doesn't do this by default.
26 <para> Solution: don't use "Open With...", avoid spaces in file names,
27 or fiddle with the appropriate registry setting:
29 HKEY_CLASSES_ROOT\Unknown\shell\openas\command
31 Notice how the "%1" argument is quoted (or not).
33 <para> This problem doesn't occur when double-clicking.
39 <sect1 id="ghci-windows">
40 <title>Running GHCi on Windows</title>
42 <para>We recommend running GHCi in a standard Windows console:
43 select the <literal>GHCi</literal> option from the start menu item
44 added by the GHC installer, or use
45 <literal>Start->Run->cmd</literal> to get a Windows console and
46 invoke <literal>ghci</literal> from there (as long as it's in your
47 <literal>PATH</literal>).</para>
49 <para>If you run GHCi in a Cygwin or MSYS shell, then the Control-C
50 behaviour is adversely affected. In one of these environments you
51 should use the <literal>ghcii.sh</literal> script to start GHCi,
52 otherwise when you hit Control-C you'll be returned to the shell
53 prompt but the GHCi process will still be running. However, even
54 using the <literal>ghcii.sh</literal> script, if you hit Control-C
55 then the GHCi process will be killed immediately, rather than
56 letting you interrupt a running program inside GHCi as it should.
57 This problem is caused by the fact that the Cygwin and MSYS shell
58 environments don't pass Control-C events to non-Cygwin child
59 processes, because in order to do that there needs to be a Windows
62 <para>There's an exception: you can use a Cygwin shell if the
63 <literal>CYGWIN</literal> environment variable does
64 <emphasis>not</emphasis> contain <literal>tty</literal>. In this
65 mode, the Cygwin shell behaves like a Windows console shell and
66 console events are propagated to child processes. Note that the
67 <literal>CYGWIN</literal> environment variable must be set
68 <emphasis>before</emphasis> starting the Cygwin shell; changing it
69 afterwards has no effect on the shell.</para>
71 <para>This problem doesn't just affect GHCi, it affects any
72 GHC-compiled program that wants to catch console events. See the
74 url="&libraryBaseLocation;/GHC-ConsoleHandler.html">GHC.ConsoleHandler</ulink>
78 <sect1 id="terminal-interaction">
80 Interacting with the terminal</title>
82 <para>By default GHC builds applications that open a console window when they start.
83 If you want to build a GUI-only application, with no console window, use the flag
84 <literal>-optl-mwindows</literal> in the link step.
87 <para> <emphasis>Warning:</emphasis> Windows GUI-only programs have no
88 stdin, stdout or stderr so using the ordinary Haskell
89 input/output functions will cause your program to fail with an
90 IO exception, such as:
92 Fail: <stdout>: hPutChar: failed (Bad file descriptor)
94 However using Debug.Trace.trace is alright because it uses
95 Windows debugging output support rather than stderr.</para>
97 <para>For some reason, Mingw ships with the <literal>readline</literal> library,
98 but not with the <literal>readline</literal> headers. As a result, GHC (like Hugs) does not
99 use <literal>readline</literal> for interactive input on Windows.
100 You can get a close simulation by using an emacs shell buffer!
105 <sect1 id="library-differences">
107 Differences in library behaviour </title>
110 Some of the standard Haskell libraries behave slightly differently on Windows.
114 On Windows, the '<literal>^Z</literal>' character is interpreted as an
115 end-of-file character, so if you read a file containing this character
116 the file will appear to end just before it. To avoid this,
117 use <literal>IOExts.openFileEx</literal> to open a file in binary
118 (untranslated) mode or change an already opened file handle into
119 binary mode using <literal>IOExts.hSetBinaryMode</literal>. The
120 <literal>IOExts</literal> module is part of the
121 <literal>lang</literal> package.
128 <sect1 id="ghci-cygwin">
130 Using GHC (and other GHC-compiled executables) with cygwin</title>
133 <title>Background</title> <para>The cygwin tools aim to provide a
134 unix-style API on top of the windows libraries, to facilitate ports of
135 unix software to windows. To this end, they introduce a unix-style
136 directory hierarchy under some root directory (typically
137 <filename>/</filename> is <filename>C:\cygwin\</filename>). Moreover,
138 everything built against the cygwin API (including the cygwin tools
139 and programs compiled with cygwin's ghc) will see / as the root of
140 their file system, happily pretending to work in a typical unix
141 environment, and finding things like <filename>/bin</filename> and <filename>/usr/include</filename> without
142 ever explicitly bothering with their actual location on the windows
143 system (probably <filename>C:\cygwin\bin</filename> and <filename>C:\cygwin\usr\include</filename>).
147 <sect2><title>The problem</title>
148 <para>GHC, by default, no longer depends on cygwin, but is a native
149 windows program. It is built using mingw, and it uses mingw's ghc
150 while compiling your Haskell sources (even if you call it from
151 cygwin's bash), but what matters here is that - just like any other
152 normal windows program - neither GHC nor the executables it produces
153 are aware of cygwin's pretended unix hierarchy. GHC will happily
154 accept either '/' or '\' as path separators, but it won't know where
155 to find <filename>/home/joe/Main.hs</filename> or <filename>/bin/bash</filename>
156 or the like. This causes all
157 kinds of fun when GHC is used from within cygwin's bash, or in
158 make-sessions running under cygwin.
162 <sect2><title>Things to do</title>
165 <para> Don't use absolute paths in make, configure & co if there is any chance
166 that those might be passed to GHC (or to GHC-compiled programs). Relative
167 paths are fine because cygwin tools are happy with them and GHC accepts
168 '/' as path-separator. And relative paths don't depend on where cygwin's
169 root directory is located, or on which partition or network drive your source
170 tree happens to reside, as long as you 'cd' there first.
174 <para> If you have to use absolute paths (beware of the innocent-looking
175 <literal>ROOT=`pwd`</literal> in makefile hierarchies or configure scripts), cygwin provides
176 a tool called <command>cygpath</command> that can convert cygwin's unix-style paths to their
177 actual windows-style counterparts. Many cygwin tools actually accept
178 absolute windows-style paths (remember, though, that you either need
179 to escape '\' or convert '\' to '/'), so you should be fine just using those
180 everywhere. If you need to use tools that do some kind of path-mangling
181 that depends on unix-style paths (one fun example is trying to interpret ':'
182 as a separator in path lists..), you can still try to convert paths using
183 <command>cygpath</command> just before they are passed to GHC and friends.
187 <para> If you don't have <command>cygpath</command>, you probably don't have cygwin and hence
188 no problems with it... unless you want to write one build process for several
189 platforms. Again, relative paths are your friend, but if you have to use
190 absolute paths, and don't want to use different tools on different platforms,
191 you can simply write a short Haskell program to print the current directory
192 (thanks to George Russell for this idea): compiled with GHC, this will give
193 you the view of the file system that GHC depends on (which will differ
194 depending on whether GHC is compiled with cygwin's gcc or mingw's
195 gcc or on a real unix system..) - that little program can also deal with
196 escaping '\' in paths. Apart from the banner and the startup time,
197 something like this would also do:
199 $ echo "Directory.getCurrentDirectory >>= putStrLn . init . tail . show " | ghci
207 <sect1 id="win32-dlls">
208 <title>Building and using Win32 DLLs
212 <emphasis>Making Haskell libraries into DLLs doesn't work on Windows at the
213 moment; we hope to re-instate this facility in the future
214 (see <xref linkend="using-shared-libs"/>). Note that
215 building an entire Haskell application as a single DLL is still supported: it's
216 just multi-DLL Haskell programs that don't work. The Windows
217 distribution of GHC contains static libraries only.</emphasis></para>
221 <indexterm><primary>Dynamic link libraries, Win32</primary></indexterm>
222 <indexterm><primary>DLLs, Win32</primary></indexterm>
223 On Win32 platforms, the compiler is capable of both producing and using
224 dynamic link libraries (DLLs) containing ghc-compiled code. This
225 section shows you how to make use of this facility.
229 Until recently, <command>strip</command> didn't work reliably on DLLs, so you
230 should test your version with care, or make sure you have the latest
231 binutils. Unfortunately, we don't know exactly which version of binutils
232 cured the problem (it was supposedly fixed some years ago).
236 <sect2 id="win32-dlls-link">
237 <title>Linking with DLLs</title>
240 The default on Win32 platforms is to link applications in such a way
241 that the executables will use the Prelude and system libraries DLLs,
242 rather than contain (large chunks of) them. This is transparent at the
250 main = putStrLn "hello, world!"
251 sh$ ghc -o main main.hs
252 ghc: module version changed to 1; reason: no old .hi file
255 -rwxr-xr-x 1 544 everyone 4608 May 3 17:11 main.exe*
263 will give you a binary as before, but the <filename>main.exe</filename>
264 generated will use the Prelude and RTS DLLs instead of linking them in
269 4K for a <literal>"hello, world"</literal> application—not bad, huh? :-)
274 <sect2 id="win32-dlls-linking-static">
275 <title>Not linking with DLLs
276 <indexterm><primary>-static option (Win32)</primary></indexterm></title>
279 If you want to build an executable that doesn't depend on any
280 ghc-compiled DLLs, use the <option>-static</option> option to link in
285 Notice that you cannot mix code that has been compiled with
286 <option>-static</option> and not, so you have to use the <option>-static</option>
287 option on all the Haskell modules that make up your application.
293 <sect2 id="win32-dlls-create">
294 <title>Creating a DLL</title>
297 <indexterm><primary>Creating a Win32 DLL</primary></indexterm>
298 <indexterm><primary>–shared</primary></indexterm>
299 Sealing up your Haskell library inside a DLL is straightforward;
300 compile up the object files that make up the library, and then build
301 the DLL by issuing a command of the form:
306 ghc –shared -o foo.dll bar.o baz.o wibble.a -lfooble
311 By feeding the ghc compiler driver the option <option>–shared</option>, it
312 will build a DLL rather than produce an executable. The DLL will
313 consist of all the object files and archives given on the command
319 To create a `static' DLL, i.e. one that does not depend on the GHC DLLs,
320 use the <option>-static</option> when compiling up your Haskell code and
326 A couple of things to notice:
335 Since DLLs correspond to packages (see <xref linkend="packages"/>) you need
336 to use <option>-package-name dll-name</option> when compiling modules that
337 belong to a DLL if you're going to call them from Haskell. Otherwise, Haskell
338 code that calls entry points in that DLL will do so incorrectly, and crash.
339 For similar reasons, you can only compile a single module tree into a DLL,
340 as <function>startupHaskell</function> needs to be able to call its
341 initialisation function, and only takes one such argument (see <xref
342 linkend="win32-dlls-foreign"/>). Hence the modules
343 you compile into a DLL must have a common root.
350 By default, the entry points of all the object files will be exported from
351 the DLL when using <option>–shared</option>. Should you want to constrain
352 this, you can specify the <emphasis>module definition file</emphasis> to use
353 on the command line as follows:
356 ghc –shared -o .... MyDef.def
359 See Microsoft documentation for details, but a module definition file
360 simply lists what entry points you want to export. Here's one that's
361 suitable when building a Haskell COM server DLL:
365 DllCanUnloadNow = DllCanUnloadNow@0
366 DllGetClassObject = DllGetClassObject@12
367 DllRegisterServer = DllRegisterServer@0
368 DllUnregisterServer = DllUnregisterServer@0
375 In addition to creating a DLL, the <option>–shared</option> option also
376 creates an import library. The import library name is derived from the
377 name of the DLL, as follows:
380 DLL: HScool.dll ==> import lib: libHScool.dll.a
383 The naming scheme may look a bit weird, but it has the purpose of allowing
384 the co-existence of import libraries with ordinary static libraries (e.g.,
385 <filename>libHSfoo.a</filename> and
386 <filename>libHSfoo.dll.a</filename>.
388 Additionally, when the compiler driver is linking in non-static mode, it
389 will rewrite occurrence of <option>-lHSfoo</option> on the command line to
390 <option>-lHSfoo.dll</option>. By doing this for you, switching from
391 non-static to static linking is simply a question of adding
392 <option>-static</option> to your command line.
402 <sect2 id="win32-dlls-foreign">
403 <title>Making DLLs to be called from other languages</title>
406 This section describes how to create DLLs to be called from other languages,
407 such as Visual Basic or C++. This is a special case of
408 <xref linkend="ffi-library" />; we'll deal with the DLL-specific issues that
409 arise below. Here's an example:
412 Use foreign export declarations to export the Haskell functions you want to
413 call from the outside. For example:
417 {-# LANGUAGE ForeignFunctionInterface #-}
420 adder :: Int -> Int -> IO Int -- gratuitous use of IO
421 adder x y = return (x+y)
423 foreign export stdcall adder :: Int -> Int -> IO Int
426 Add some helper code that starts up and shuts down the Haskell RTS:
430 #include <Rts.h>
432 extern void __stginit_Adder(void);
437 char* argv[] = {"ghcDll", NULL}; // argv must end with NULL
439 // Initialize Haskell runtime
441 hs_init(&argc, &args);
443 // Tell Haskell about all root modules
444 hs_add_root(__stginit_Adder);
453 Here, <literal>Adder</literal> is the name of the root module in the module
454 tree (as mentioned above, there must be a single root module, and hence a
455 single module tree in the DLL). Compile everything up:
460 ghc -shared -o Adder.dll Adder.o Adder_stub.o StartEnd.o
463 Now the file <filename>Adder.dll</filename> can be used from other
464 programming languages. Before calling any functions in Adder it is necessary
465 to call <literal>HsStart</literal>, and at the very end call
466 <literal>HsEnd</literal>.
469 <emphasis>Warning:</emphasis> It may appear tempting to use
470 <literal>DllMain</literal> to call
471 <literal>hs_init</literal>/<literal>hs_exit</literal>, but this won't work
472 (particularly if you compile with <literal>-threaded</literal>). There are
473 severe restrictions on which actions can be performed during
474 <literal>DllMain</literal>, and <literal>hs_init</literal> violates these
475 restrictions, which can lead to your dll freezing during startup (see
476 <ulink url="http://hackage.haskell.org/trac/ghc/ticket/3605">bug
480 <sect3 id="win32-dlls-vba">
481 <title>Using from VBA</title>
484 An example of using <filename>Adder.dll</filename> from VBA is:
487 Private Declare Function Adder Lib "Adder.dll" Alias "adder@8" _
488 (ByVal x As Long, ByVal y As Long) As Long
490 Private Declare Sub HsStart Lib "Adder.dll" ()
491 Private Declare Sub HsEnd Lib "Adder.dll" ()
493 Private Sub Document_Close()
497 Private Sub Document_Open()
502 MsgBox "12 + 5 = " & Adder(12, 5)
506 This example uses the
507 <literal>Document_Open</literal>/<literal>Close</literal> functions of
508 Microsoft Word, but provided <literal>HsStart</literal> is called before the
509 first function, and <literal>HsEnd</literal> after the last, then it will
514 <sect3 id="win32-dlls-c++">
515 <title>Using from C++</title>
518 An example of using <filename>Adder.dll</filename> from C++ is:
524 #include "Adder_stub.h"
525 #include <stdio.h>
535 // can now safely call functions from the DLL
536 printf("12 + 5 = %i\n", adder(12,5)) ;
542 This can be compiled and run with:
545 $ ghc -o tester Tester.cpp Adder.dll.a
558 ;;; Local Variables: ***
559 ;;; sgml-parent-document: ("users_guide.xml" "book" "chapter") ***