1 <?xml version="1.0" encoding="iso-8859-1"?>
3 <title>Running GHC on Win32 systems</title>
7 Starting GHC on Win32 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.
41 Interacting with the terminal</title>
43 <para>By default GHC builds applications that open a console window when they start.
44 If you want to build a GUI-only application, with no console window, use the flag
45 <literal>-optl-mwindows</literal> in the link step.
48 <para> <emphasis>Warning:</emphasis> Windows GUI-only programs have no
49 stdin, stdout or stderr so using the ordinary Haskell
50 input/output functions will cause your program to fail with an
51 IO exception, such as:
53 Fail: <stdout>: hPutChar: failed (Bad file descriptor)
55 However using Debug.Trace.trace is alright because it uses
56 Windows debugging output support rather than stderr.</para>
58 <para>For some reason, Mingw ships with the <literal>readline</literal> library,
59 but not with the <literal>readline</literal> headers. As a result, GHC (like Hugs) does not
60 use <literal>readline</literal> for interactive input on Windows.
61 You can get a close simulation by using an emacs shell buffer!
68 Differences in library behaviour </title>
71 Some of the standard Haskell libraries behave slightly differently on Windows.
75 On Windows, the '<literal>^Z</literal>' character is interpreted as an
76 end-of-file character, so if you read a file containing this character
77 the file will appear to end just before it. To avoid this,
78 use <literal>IOExts.openFileEx</literal> to open a file in binary
79 (untranslated) mode or change an already opened file handle into
80 binary mode using <literal>IOExts.hSetBinaryMode</literal>. The
81 <literal>IOExts</literal> module is part of the
82 <literal>lang</literal> package.
91 Using GHC (and other GHC-compiled executables) with cygwin</title>
94 <title>Background</title> <para>The cygwin tools aim to provide a
95 unix-style API on top of the windows libraries, to facilitate ports of
96 unix software to windows. To this end, they introduce a unix-style
97 directory hierarchy under some root directory (typically
98 <filename>/</filename> is <filename>C:\cygwin\</filename>). Moreover,
99 everything built against the cygwin API (including the cygwin tools
100 and programs compiled with cygwin's ghc) will see / as the root of
101 their file system, happily pretending to work in a typical unix
102 environment, and finding things like <filename>/bin</filename> and <filename>/usr/include</filename> without
103 ever explicitly bothering with their actual location on the windows
104 system (probably <filename>C:\cygwin\bin</filename> and <filename>C:\cygwin\usr\include</filename>).
108 <sect2><title>The problem</title>
109 <para>GHC, by default, no longer depends on cygwin, but is a native
110 windows program. It is built using mingw, and it uses mingw's ghc
111 while compiling your Haskell sources (even if you call it from
112 cygwin's bash), but what matters here is that - just like any other
113 normal windows program - neither GHC nor the executables it produces
114 are aware of cygwin's pretended unix hierarchy. GHC will happily
115 accept either '/' or '\' as path separators, but it won't know where
116 to find <filename>/home/joe/Main.hs</filename> or <filename>/bin/bash</filename>
117 or the like. This causes all
118 kinds of fun when GHC is used from within cygwin's bash, or in
119 make-sessions running under cygwin.
123 <sect2><title>Things to do</title>
126 <para> Don't use absolute paths in make, configure & co if there is any chance
127 that those might be passed to GHC (or to GHC-compiled programs). Relative
128 paths are fine because cygwin tools are happy with them and GHC accepts
129 '/' as path-separator. And relative paths don't depend on where cygwin's
130 root directory is located, or on which partition or network drive your source
131 tree happens to reside, as long as you 'cd' there first.
135 <para> If you have to use absolute paths (beware of the innocent-looking
136 <literal>ROOT=`pwd`</literal> in makefile hierarchies or configure scripts), cygwin provides
137 a tool called <command>cygpath</command> that can convert cygwin's unix-style paths to their
138 actual windows-style counterparts. Many cygwin tools actually accept
139 absolute windows-style paths (remember, though, that you either need
140 to escape '\' or convert '\' to '/'), so you should be fine just using those
141 everywhere. If you need to use tools that do some kind of path-mangling
142 that depends on unix-style paths (one fun example is trying to interpret ':'
143 as a separator in path lists..), you can still try to convert paths using
144 <command>cygpath</command> just before they are passed to GHC and friends.
148 <para> If you don't have <command>cygpath</command>, you probably don't have cygwin and hence
149 no problems with it... unless you want to write one build process for several
150 platforms. Again, relative paths are your friend, but if you have to use
151 absolute paths, and don't want to use different tools on different platforms,
152 you can simply write a short Haskell program to print the current directory
153 (thanks to George Russell for this idea): compiled with GHC, this will give
154 you the view of the file system that GHC depends on (which will differ
155 depending on whether GHC is compiled with cygwin's gcc or mingw's
156 gcc or on a real unix system..) - that little program can also deal with
157 escaping '\' in paths. Apart from the banner and the startup time,
158 something like this would also do:
160 $ echo "Directory.getCurrentDirectory >>= putStrLn . init . tail . show " | ghci
168 <sect1 id="win32-dlls">
169 <title>Building and using Win32 DLLs
173 <indexterm><primary>Dynamic link libraries, Win32</primary></indexterm>
174 <indexterm><primary>DLLs, Win32</primary></indexterm>
175 On Win32 platforms, the compiler is capable of both producing and using
176 dynamic link libraries (DLLs) containing ghc-compiled code. This
177 section shows you how to make use of this facility.
181 Until recently, <command>strip</command> didn't work reliably on DLLs, so you
182 should test your version with care, or make sure you have the latest
183 binutils. Unfortunately, we don't know exactly which version of binutils
184 cured the problem (it was supposedly fixed some years ago).
188 <sect2 id="win32-dlls-link">
189 <title>Linking with DLLs</title>
192 The default on Win32 platforms is to link applications in such a way
193 that the executables will use the Prelude and system libraries DLLs,
194 rather than contain (large chunks of) them. This is transparent at the
202 main = putStrLn "hello, world!"
203 sh$ ghc -o main main.hs
204 ghc: module version changed to 1; reason: no old .hi file
207 -rwxr-xr-x 1 544 everyone 4608 May 3 17:11 main.exe*
215 will give you a binary as before, but the <filename>main.exe</filename>
216 generated will use the Prelude and RTS DLLs instead of linking them in
221 4K for a <literal>"hello, world"</literal> application—not bad, huh? :-)
226 <sect2 id="win32-dlls-linking-static">
227 <title>Not linking with DLLs
228 <indexterm><primary>-static option (Win32)</primary></indexterm></title>
231 If you want to build an executable that doesn't depend on any
232 ghc-compiled DLLs, use the <option>-static</option> option to link in
237 Notice that you cannot mix code that has been compiled with
238 <option>-static</option> and not, so you have to use the <option>-static</option>
239 option on all the Haskell modules that make up your application.
244 <sect2 id="win32-dlls-create">
245 <title>Creating a DLL</title>
248 <emphasis>Making libraries into DLLs doesn't work on Windows at the
249 moment (and is no longer supported); however, all the machinery is
250 still there. If you're interested, contact the GHC team. Note that
251 building an entire Haskell application as a DLL is still supported
252 (it's just inter-DLL Haskell calls that don't work).</emphasis>
253 <indexterm><primary>Creating a Win32 DLL</primary></indexterm>
254 <indexterm><primary>––mk-dll</primary></indexterm>
255 Sealing up your Haskell library inside a DLL is straightforward;
256 compile up the object files that make up the library, and then build
257 the DLL by issuing a command of the form:
262 ghc ––mk-dll -o foo.dll bar.o baz.o wibble.a -lfooble
267 By feeding the ghc compiler driver the option <option>––mk-dll</option>, it
268 will build a DLL rather than produce an executable. The DLL will
269 consist of all the object files and archives given on the command
274 To create a `static' DLL, i.e. one that does not depend on the GHC DLLs,
275 use the <option>-static</option> when compiling up your Haskell code and
280 A couple of things to notice:
288 Since DLLs correspond to packages (see <xref linkend="packages"/>) you need
289 to use <option>-package-name dll-name</option> when compiling modules that
290 belong to a DLL if you're going to call them from Haskell. Otherwise, Haskell
291 code that calls entry points in that DLL will do so incorrectly, and crash.
292 For similar reasons, you can only compile a single module tree into a DLL,
293 as <function>startupHaskell</function> needs to be able to call its
294 initialisation function, and only takes one such argument (see <xref
295 linkend="win32-dlls-foreign"/>). Hence the modules
296 you compile into a DLL must have a common root.
302 By default, the entry points of all the object files will be exported from
303 the DLL when using <option>––mk-dll</option>. Should you want to constrain
304 this, you can specify the <emphasis>module definition file</emphasis> to use
305 on the command line as follows:
308 ghc ––mk-dll -o .... -optdll--def -optdllMyDef.def
311 See Microsoft documentation for details, but a module definition file
312 simply lists what entry points you want to export. Here's one that's
313 suitable when building a Haskell COM server DLL:
317 DllCanUnloadNow = DllCanUnloadNow@0
318 DllGetClassObject = DllGetClassObject@12
319 DllRegisterServer = DllRegisterServer@0
320 DllUnregisterServer = DllUnregisterServer@0
327 In addition to creating a DLL, the <option>––mk-dll</option> option also
328 creates an import library. The import library name is derived from the
329 name of the DLL, as follows:
332 DLL: HScool.dll ==> import lib: libHScool_imp.a
335 The naming scheme may look a bit weird, but it has the purpose of allowing
336 the co-existence of import libraries with ordinary static libraries (e.g.,
337 <filename>libHSfoo.a</filename> and
338 <filename>libHSfoo_imp.a</filename>.
340 Additionally, when the compiler driver is linking in non-static mode, it
341 will rewrite occurrence of <option>-lHSfoo</option> on the command line to
342 <option>-lHSfoo_imp</option>. By doing this for you, switching from
343 non-static to static linking is simply a question of adding
344 <option>-static</option> to your command line.
354 <sect2 id="win32-dlls-foreign">
355 <title>Making DLLs to be called from other languages</title>
359 If you want to package up Haskell code to be called from other languages,
360 such as Visual Basic or C++, there are some extra things it is useful to
361 know. The dirty details are in the <emphasis>Foreign Function
362 Interface</emphasis> definition, but it can be tricky to work out how to
363 combine this with DLL building, so here's an example:
371 Use <literal>foreign export</literal> declarations to export the Haskell
372 functions you want to call from the outside. For example,
377 adder :: Int -> Int -> IO Int -- gratuitous use of IO
378 adder x y = return (x+y)
380 foreign export stdcall adder :: Int -> Int -> IO Int
390 ghc -c adder.hs -fglasgow-exts
393 This will produce two files, adder.o and adder_stub.o
399 compile up a <function>DllMain()</function> that starts up the Haskell
400 RTS-––a possible implementation is:
403 #include <windows.h>
404 #include <Rts.h>
406 EXTFUN(__stginit_Adder);
408 static char* args[] = { "ghcDll", NULL };
409 /* N.B. argv arrays must end with NULL */
418 if (reason == DLL_PROCESS_ATTACH) {
419 /* By now, the RTS DLL should have been hoisted in, but we need to start it up. */
420 startupHaskell(1, args, __stginit_Adder);
427 Here, <literal>Adder</literal> is the name of the root module in the module
428 tree (as mentioned above, there must be a single root module, and hence a
429 single module tree in the DLL).
444 ghc ––mk-dll -o adder.dll adder.o adder_stub.o dllMain.o
452 Start using <function>adder</function> from VBA-––here's how I would
453 <constant>Declare</constant> it:
456 Private Declare Function adder Lib "adder.dll" Alias "adder@8"
457 (ByVal x As Long, ByVal y As Long) As Long
460 Since this Haskell DLL depends on a couple of the DLLs that come with GHC,
461 make sure that they are in scope/visible.
465 Building statically linked DLLs is the same as in the previous section: it
466 suffices to add <option>-static</option> to the commands used to compile up
467 the Haskell source and build the DLL.
480 ;;; Local Variables: ***
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