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>For some reason, Mingw ships with the <literal>readline</literal> library,
49 but not with the <literal>readline</literal> headers. As a result, GHC (like Hugs) does not
50 use <literal>readline</literal> for interactive input on Windows.
51 You can get a close simulation by using an emacs shell buffer!
58 Differences in library behaviour </title>
61 Some of the standard Haskell libraries behave slightly differently on Windows.
65 On Windows, the '<literal>^Z</literal>' character is interpreted as an
66 end-of-file character, so if you read a file containing this character
67 the file will appear to end just before it. To avoid this,
68 use <literal>IOExts.openFileEx</literal> to open a file in binary
69 (untranslated) mode or change an already opened file handle into
70 binary mode using <literal>IOExts.hSetBinaryMode</literal>. The
71 <literal>IOExts</literal> module is part of the
72 <literal>lang</literal> package.
81 Using GHC (and other GHC-compiled executables) with cygwin</title>
84 <title>Background</title> <para>The cygwin tools aim to provide a
85 unix-style API on top of the windows libraries, to facilitate ports of
86 unix software to windows. To this end, they introduce a unix-style
87 directory hierarchy under some root directory (typically
88 <filename>/</filename> is <filename>C:\cygwin\</filename>). Moreover,
89 everything built against the cygwin API (including the cygwin tools
90 and programs compiled with cygwin's ghc) will see / as the root of
91 their file system, happily pretending to work in a typical unix
92 environment, and finding things like <filename>/bin</filename> and <filename>/usr/include</filename> without
93 ever explicitly bothering with their actual location on the windows
94 system (probably <filename>C:\cygwin\bin</filename> and <filename>C:\cygwin\usr\include</filename>).
98 <sect2><title>The problem</title>
99 <para>GHC, by default, no longer depends on cygwin, but is a native
100 windows program. It is built using mingw, and it uses mingw's ghc
101 while compiling your Haskell sources (even if you call it from
102 cygwin's bash), but what matters here is that - just like any other
103 normal windows program - neither GHC nor the executables it produces
104 are aware of cygwin's pretended unix hierarchy. GHC will happily
105 accept either '/' or '\' as path separators, but it won't know where
106 to find <filename>/home/joe/Main.hs</filename> or <filename>/bin/bash</filename>
107 or the like. This causes all
108 kinds of fun when GHC is used from within cygwin's bash, or in
109 make-sessions running under cygwin.
113 <sect2><title>Things to do</title>
116 <para> Don't use absolute paths in make, configure & co if there is any chance
117 that those might be passed to GHC (or to GHC-compiled programs). Relative
118 paths are fine because cygwin tools are happy with them and GHC accepts
119 '/' as path-separator. And relative paths don't depend on where cygwin's
120 root directory is located, or on which partition or network drive your source
121 tree happens to reside, as long as you 'cd' there first.
125 <para> If you have to use absolute paths (beware of the innocent-looking
126 <literal>ROOT=`pwd`</literal> in makefile hierarchies or configure scripts), cygwin provides
127 a tool called <command>cygpath</command> that can convert cygwin's unix-style paths to their
128 actual windows-style counterparts. Many cygwin tools actually accept
129 absolute windows-style paths (remember, though, that you either need
130 to escape '\' or convert '\' to '/'), so you should be fine just using those
131 everywhere. If you need to use tools that do some kind of path-mangling
132 that depends on unix-style paths (one fun example is trying to interpret ':'
133 as a separator in path lists..), you can still try to convert paths using
134 <command>cygpath</command> just before they are passed to GHC and friends.
138 <para> If you don't have <command>cygpath</command>, you probably don't have cygwin and hence
139 no problems with it... unless you want to write one build process for several
140 platforms. Again, relative paths are your friend, but if you have to use
141 absolute paths, and don't want to use different tools on different platforms,
142 you can simply write a short Haskell program to print the current directory
143 (thanks to George Russell for this idea): compiled with GHC, this will give
144 you the view of the file system that GHC depends on (which will differ
145 depending on whether GHC is compiled with cygwin's gcc or mingw's
146 gcc or on a real unix system..) - that little program can also deal with
147 escaping '\' in paths. Apart from the banner and the startup time,
148 something like this would also do:
150 $ echo "Directory.getCurrentDirectory >>= putStrLn . init . tail . show " | ghci
158 <sect1 id="win32-dlls">
159 <title>Building and using Win32 DLLs
163 <indexterm><primary>Dynamic link libraries, Win32</primary></indexterm>
164 <indexterm><primary>DLLs, Win32</primary></indexterm>
165 On Win32 platforms, the compiler is capable of both producing and using
166 dynamic link libraries (DLLs) containing ghc-compiled code. This
167 section shows you how to make use of this facility.
171 Until recently, <command>strip</command> didn't work reliably on DLLs, so you
172 should test your version with care, or make sure you have the latest
173 binutils. Unfortunately, we don't know exactly which version of binutils
174 cured the problem (it was supposedly fixed some years ago).
178 <sect2 id="win32-dlls-link">
179 <title>Linking with DLLs</title>
182 The default on Win32 platforms is to link applications in such a way
183 that the executables will use the Prelude and system libraries DLLs,
184 rather than contain (large chunks of) them. This is transparent at the
192 main = putStrLn "hello, world!"
193 sh$ ghc -o main main.hs
194 ghc: module version changed to 1; reason: no old .hi file
197 -rwxr-xr-x 1 544 everyone 4608 May 3 17:11 main.exe*
205 will give you a binary as before, but the <filename>main.exe</filename>
206 generated will use the Prelude and RTS DLLs instead of linking them in
211 4K for a <literal>"hello, world"</literal> application—not bad, huh? :-)
216 <sect2 id="win32-dlls-linking-static">
217 <title>Not linking with DLLs
218 <indexterm><primary>-static option (Win32)</primary></indexterm></title>
221 If you want to build an executable that doesn't depend on any
222 ghc-compiled DLLs, use the <option>-static</option> option to link in
227 Notice that you cannot mix code that has been compiled with
228 <option>-static</option> and not, so you have to use the <option>-static</option>
229 option on all the Haskell modules that make up your application.
234 <sect2 id="win32-dlls-create">
235 <title>Creating a DLL</title>
238 <emphasis>Making libraries into DLLs doesn't work on Windows at the
239 moment (and is no longer supported); however, all the machinery is
240 still there. If you're interested, contact the GHC team. Note that
241 building an entire Haskell application as a DLL is still supported
242 (it's just inter-DLL Haskell calls that don't work).</emphasis>
243 <indexterm><primary>Creating a Win32 DLL</primary></indexterm>
244 <indexterm><primary>––mk-dll</primary></indexterm>
245 Sealing up your Haskell library inside a DLL is straightforward;
246 compile up the object files that make up the library, and then build
247 the DLL by issuing a command of the form:
252 ghc ––mk-dll -o foo.dll bar.o baz.o wibble.a -lfooble
257 By feeding the ghc compiler driver the option <option>––mk-dll</option>, it
258 will build a DLL rather than produce an executable. The DLL will
259 consist of all the object files and archives given on the command
264 To create a `static' DLL, i.e. one that does not depend on the GHC DLLs,
265 use the <option>-static</option> when compiling up your Haskell code and
270 A couple of things to notice:
278 Since DLLs correspond to packages (see <xref linkend="packages"/>) you need
279 to use <option>-package-name dll-name</option> when compiling modules that
280 belong to a DLL if you're going to call them from Haskell. Otherwise, Haskell
281 code that calls entry points in that DLL will do so incorrectly, and crash.
282 For similar reasons, you can only compile a single module tree into a DLL,
283 as <function>startupHaskell</function> needs to be able to call its
284 initialisation function, and only takes one such argument (see <xref
285 linkend="win32-dlls-foreign"/>). Hence the modules
286 you compile into a DLL must have a common root.
292 By default, the entry points of all the object files will be exported from
293 the DLL when using <option>––mk-dll</option>. Should you want to constrain
294 this, you can specify the <emphasis>module definition file</emphasis> to use
295 on the command line as follows:
298 ghc ––mk-dll -o .... -optdll--def -optdllMyDef.def
301 See Microsoft documentation for details, but a module definition file
302 simply lists what entry points you want to export. Here's one that's
303 suitable when building a Haskell COM server DLL:
307 DllCanUnloadNow = DllCanUnloadNow@0
308 DllGetClassObject = DllGetClassObject@12
309 DllRegisterServer = DllRegisterServer@0
310 DllUnregisterServer = DllUnregisterServer@0
317 In addition to creating a DLL, the <option>––mk-dll</option> option also
318 creates an import library. The import library name is derived from the
319 name of the DLL, as follows:
322 DLL: HScool.dll ==> import lib: libHScool_imp.a
325 The naming scheme may look a bit weird, but it has the purpose of allowing
326 the co-existence of import libraries with ordinary static libraries (e.g.,
327 <filename>libHSfoo.a</filename> and
328 <filename>libHSfoo_imp.a</filename>.
330 Additionally, when the compiler driver is linking in non-static mode, it
331 will rewrite occurrence of <option>-lHSfoo</option> on the command line to
332 <option>-lHSfoo_imp</option>. By doing this for you, switching from
333 non-static to static linking is simply a question of adding
334 <option>-static</option> to your command line.
344 <sect2 id="win32-dlls-foreign">
345 <title>Making DLLs to be called from other languages</title>
349 If you want to package up Haskell code to be called from other languages,
350 such as Visual Basic or C++, there are some extra things it is useful to
351 know. The dirty details are in the <emphasis>Foreign Function
352 Interface</emphasis> definition, but it can be tricky to work out how to
353 combine this with DLL building, so here's an example:
361 Use <literal>foreign export</literal> declarations to export the Haskell
362 functions you want to call from the outside. For example,
367 adder :: Int -> Int -> IO Int -- gratuitous use of IO
368 adder x y = return (x+y)
370 foreign export stdcall adder :: Int -> Int -> IO Int
380 ghc -c adder.hs -fglasgow-exts
383 This will produce two files, adder.o and adder_stub.o
389 compile up a <function>DllMain()</function> that starts up the Haskell
390 RTS-––a possible implementation is:
393 #include <windows.h>
394 #include <Rts.h>
396 EXTFUN(__stginit_Adder);
398 static char* args[] = { "ghcDll", NULL };
399 /* N.B. argv arrays must end with NULL */
408 if (reason == DLL_PROCESS_ATTACH) {
409 /* By now, the RTS DLL should have been hoisted in, but we need to start it up. */
410 startupHaskell(1, args, __stginit_Adder);
417 Here, <literal>Adder</literal> is the name of the root module in the module
418 tree (as mentioned above, there must be a single root module, and hence a
419 single module tree in the DLL).
434 ghc ––mk-dll -o adder.dll adder.o adder_stub.o dllMain.o
442 Start using <function>adder</function> from VBA-––here's how I would
443 <constant>Declare</constant> it:
446 Private Declare Function adder Lib "adder.dll" Alias "adder@8"
447 (ByVal x As Long, ByVal y As Long) As Long
450 Since this Haskell DLL depends on a couple of the DLLs that come with GHC,
451 make sure that they are in scope/visible.
455 Building statically linked DLLs is the same as in the previous section: it
456 suffices to add <option>-static</option> to the commands used to compile up
457 the Haskell source and build the DLL.
470 ;;; Local Variables: ***
472 ;;; sgml-parent-document: ("users_guide.xml" "book" "chapter") ***