2 <title>Running GHC on Win32 systems</title>
6 Starting GHC on Win32 platforms</title>
9 The installer that installs GHC on Win32 also sets up the file-suffix associations
10 for ".hs" and ".lhs" files so that double-clicking them starts <command>ghci</command>.
13 Be aware of that <command>ghc</command> and <command>ghci</command> do
14 require filenames containing spaces to be escaped using quotes:
16 c:\ghc\bin\ghci "c:\\Program Files\\Haskell\\Project.hs"
18 If the quotes are left off in the above command, <command>ghci</command> will
19 interpret the filename as two, "c:\\Program" and "Files\\Haskell\\Project.hs".
22 <!-- not clear whether there are current editions of Win32 OSes that
23 doesn't do this by default.
25 <para> Solution: don't use "Open With...", avoid spaces in file names,
26 or fiddle with the appropriate registry setting:
28 HKEY_CLASSES_ROOT\Unknown\shell\openas\command
30 Notice how the "%1" argument is quoted (or not).
32 <para> This problem doesn't occur when double-clicking.
40 Avoiding the console window</title>
42 <para>By default GHC builds applications that open a console window when they start.
43 If you want to build a GUI-only application, with no console window, use the flag
44 <literal>-optl-mwindows</literal> in the link step.
50 Using GHC (and other GHC-compiled executables) with cygwin</title>
53 <title>Background</title> <para>The cygwin tools aim to provide a
54 unix-style API on top of the windows libraries, to facilitate ports of
55 unix software to windows. To this end, they introduce a unix-style
56 directory hierarchy under some root directory (typically
57 <filename>/</filename> is <filename>C:\cygwin\</filename>). Moreover,
58 everything built against the cygwin API (including the cygwin tools
59 and programs compiled with cygwin's ghc) will see / as the root of
60 their file system, happily pretending to work in a typical unix
61 environment, and finding things like <filename>/bin</filename> and <filename>/usr/include</filename> without
62 ever explicitly bothering with their actual location on the windows
63 system (probably <filename>C:\cygwin\bin</filename> and <filename>C:\cygwin\usr\include</filename>).
67 <sect2><title>The problem</title>
68 <para>GHC, by default, no longer depends on cygwin, but is a native
69 windows program. It is built using mingw, and it uses mingw's ghc
70 while compiling your Haskell sources (even if you call it from
71 cygwin's bash), but what matters here is that - just like any other
72 normal windows program - neither GHC nor the executables it produces
73 are aware of cygwin's pretended unix hierarchy. GHC will happily
74 accept either '/' or '\' as path separators, but it won't know where
75 to find <filename>/home/joe/Main.hs</filename> or <filename>/bin/bash</filename>
76 or the like. This causes all
77 kinds of fun when GHC is used from within cygwin's bash, or in
78 make-sessions running under cygwin.
82 <sect2><title>Things to do</title>
85 <para> Don't use absolute paths in make, configure & co if there is any chance
86 that those might be passed to GHC (or to GHC-compiled programs). Relative
87 paths are fine because cygwin tools are happy with them and GHC accepts
88 '/' as path-separator. And relative paths don't depend on where cygwin's
89 root directory is located, or on which partition or network drive your source
90 tree happens to reside, as long as you 'cd' there first.
94 <para> If you have to use absolute paths (beware of the innocent-looking
95 <literal>ROOT=`pwd`</literal> in makefile hierarchies or configure scripts), cygwin provides
96 a tool called <command>cygpath</command> that can convert cygwin's unix-style paths to their
97 actual windows-style counterparts. Many cygwin tools actually accept
98 absolute windows-style paths (remember, though, that you either need
99 to escape '\' or convert '\' to '/'), so you should be fine just using those
100 everywhere. If you need to use tools that do some kind of path-mangling
101 that depends on unix-style paths (one fun example is trying to interpret ':'
102 as a separator in path lists..), you can still try to convert paths using
103 <command>cygpath</command> just before they are passed to GHC and friends.
107 <para> If you don't have <command>cygpath</command>, you probably don't have cygwin and hence
108 no problems with it... unless you want to write one build process for several
109 platforms. Again, relative paths are your friend, but if you have to use
110 absolute paths, and don't want to use different tools on different platforms,
111 you can simply write a short Haskell program to print the current directory
112 (thanks to George Russell for this idea): compiled with GHC, this will give
113 you the view of the file system that GHC depends on (which will differ
114 depending on whether GHC is compiled with cygwin's gcc or mingw's
115 gcc or on a real unix system..) - that little program can also deal with
116 escaping '\' in paths. Apart from the banner and the startup time,
117 something like this would also do:
119 $ echo "Directory.getCurrentDirectory >>= putStrLn . init . tail . show " | ghci
127 <sect1 id="win32-dlls">
128 <Title>Building and using Win32 DLLs
132 <IndexTerm><Primary>Dynamic link libraries, Win32</Primary></IndexTerm>
133 <IndexTerm><Primary>DLLs, Win32</Primary></IndexTerm>
134 On Win32 platforms, the compiler is capable of both producing and using
135 dynamic link libraries (DLLs) containing ghc-compiled code. This
136 section shows you how to make use of this facility.
140 Until recently, <Command>strip</Command> didn't work reliably on DLLs, so you
141 should test your version with care, or make sure you have the latest
142 binutils. Unfortunately, we don't know exactly which version of binutils
143 cured the problem (it was supposedly fixed some years ago).
147 <Sect2 id="win32-dlls-link">
148 <Title>Linking with DLLs
152 The default on Win32 platforms is to link applications in such a way
153 that the executables will use the Prelude and system libraries DLLs,
154 rather than contain (large chunks of) them. This is transparent at the
162 main = putStrLn "hello, world!"
163 sh$ ghc -o main main.hs
164 ghc: module version changed to 1; reason: no old .hi file
167 -rwxr-xr-x 1 544 everyone 4608 May 3 17:11 main.exe*
175 will give you a binary as before, but the <Filename>main.exe</Filename>
176 generated will use the Prelude and RTS DLLs instead of linking them in
181 4K for a <Literal>"hello, world"</Literal> application—not bad, huh? :-)
186 <Sect2 id="win32-dlls-linking-static">
187 <Title>Not linking with DLLs
188 <IndexTerm><Primary>-static option (Win32)</Primary></IndexTerm></Title>
191 If you want to build an executable that doesn't depend on any
192 ghc-compiled DLLs, use the <Option>-static</Option> option to link in
197 Notice that you cannot mix code that has been compiled with
198 <Option>-static</Option> and not, so you have to use the <Option>-static</Option>
199 option on all the Haskell modules that make up your application.
204 <Sect2 id="win32-dlls-create">
205 <Title>Creating a DLL
209 <emphasis>Making libraries into DLLs doesn't work on Windows at the
210 moment (and is no longer supported); however, all the machinery is
211 still there. If you're interested, contact the GHC team. Note that
212 building an entire Haskell application as a DLL is still supported
213 (it's just inter-DLL Haskell calls that don't work).</emphasis>
214 <IndexTerm><Primary>Creating a Win32 DLL</Primary></IndexTerm>
215 <IndexTerm><Primary>––mk-dll</Primary></IndexTerm>
216 Sealing up your Haskell library inside a DLL is straightforward;
217 compile up the object files that make up the library, and then build
218 the DLL by issuing a command of the form:
223 ghc ––mk-dll -o foo.dll bar.o baz.o wibble.a -lfooble
228 By feeding the ghc compiler driver the option <Option>––mk-dll</Option>, it
229 will build a DLL rather than produce an executable. The DLL will
230 consist of all the object files and archives given on the command
235 To create a `static' DLL, i.e. one that does not depend on the GHC DLLs,
236 use the <Option>-static</Option> when compiling up your Haskell code and
241 A couple of things to notice:
249 Since DLLs correspond to packages (see <XRef LinkEnd="packages">) you need
250 to use <Option>-package-name dll-name</Option> when compiling modules that
251 belong to a DLL if you're going to call them from Haskell. Otherwise, Haskell
252 code that calls entry points in that DLL will do so incorrectly, and crash.
253 For similar reasons, you can only compile a single module tree into a DLL,
254 as <Function>startupHaskell</Function> needs to be able to call its
255 initialisation function, and only takes one such argument (see <XRef
256 LinkEnd="win32-dlls-foreign">). Hence the modules
257 you compile into a DLL must have a common root.
263 By default, the entry points of all the object files will be exported from
264 the DLL when using <Option>––mk-dll</Option>. Should you want to constrain
265 this, you can specify the <Emphasis>module definition file</Emphasis> to use
266 on the command line as follows:
269 ghc ––mk-dll -o .... -optdll--def -optdllMyDef.def
272 See Microsoft documentation for details, but a module definition file
273 simply lists what entry points you want to export. Here's one that's
274 suitable when building a Haskell COM server DLL:
278 DllCanUnloadNow = DllCanUnloadNow@0
279 DllGetClassObject = DllGetClassObject@12
280 DllRegisterServer = DllRegisterServer@0
281 DllUnregisterServer = DllUnregisterServer@0
288 In addition to creating a DLL, the <Option>––mk-dll</Option> option also
289 creates an import library. The import library name is derived from the
290 name of the DLL, as follows:
293 DLL: HScool.dll ==> import lib: libHScool_imp.a
296 The naming scheme may look a bit weird, but it has the purpose of allowing
297 the co-existence of import libraries with ordinary static libraries (e.g.,
298 <Filename>libHSfoo.a</Filename> and
299 <Filename>libHSfoo_imp.a</Filename>.
301 Additionally, when the compiler driver is linking in non-static mode, it
302 will rewrite occurrence of <Option>-lHSfoo</Option> on the command line to
303 <Option>-lHSfoo_imp</Option>. By doing this for you, switching from
304 non-static to static linking is simply a question of adding
305 <Option>-static</Option> to your command line.
315 <Sect2 id="win32-dlls-foreign">
316 <Title>Making DLLs to be called from other languages</Title>
320 If you want to package up Haskell code to be called from other languages,
321 such as Visual Basic or C++, there are some extra things it is useful to
322 know. The dirty details are in the <Emphasis>Foreign Function
323 Interface</Emphasis> definition, but it can be tricky to work out how to
324 combine this with DLL building, so here's an example:
332 Use <Literal>foreign export</Literal> declarations to export the Haskell
333 functions you want to call from the outside. For example,
338 adder :: Int -> Int -> IO Int -- gratuitous use of IO
339 adder x y = return (x+y)
341 foreign export stdcall adder :: Int -> Int -> IO Int
351 ghc -c adder.hs -fglasgow-exts
354 This will produce two files, adder.o and adder_stub.o
360 compile up a <Function>DllMain()</Function> that starts up the Haskell
361 RTS-––a possible implementation is:
364 #include <windows.h>
365 #include <Rts.h>
367 EXTFUN(__stginit_Adder);
369 static char* args[] = { "ghcDll", NULL };
370 /* N.B. argv arrays must end with NULL */
379 if (reason == DLL_PROCESS_ATTACH) {
380 /* By now, the RTS DLL should have been hoisted in, but we need to start it up. */
381 startupHaskell(1, args, __stginit_Adder);
388 Here, <Literal>Adder</Literal> is the name of the root module in the module
389 tree (as mentioned above, there must be a single root module, and hence a
390 single module tree in the DLL).
405 ghc ––mk-dll -o adder.dll adder.o adder_stub.o dllMain.o
413 Start using <Function>adder</Function> from VBA-––here's how I would
414 <Constant>Declare</Constant> it:
417 Private Declare Function adder Lib "adder.dll" Alias "adder@8"
418 (ByVal x As Long, ByVal y As Long) As Long
421 Since this Haskell DLL depends on a couple of the DLLs that come with GHC,
422 make sure that they are in scope/visible.
426 Building statically linked DLLs is the same as in the previous section: it
427 suffices to add <Option>-static</Option> to the commands used to compile up
428 the Haskell source and build the DLL.
441 ;;; Local Variables: ***
443 ;;; sgml-parent-document: ("users_guide.sgml" "book" "chapter") ***