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 Interacting with the terminal</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.
47 <para>For some reason, Mingw ships with the <literal>readline</literal> library,
48 but not with the <literal>readline</literal> headers. As a result, GHC (like Hugs) does not
49 use <literal>readline</literal> for interactive input on Windows.
50 You can get a close simulation by using an emacs shell buffer!
57 Differences in library behaviour </title>
60 Some of the standard Haskell libraries behave slightly differently on Windows.
64 On Windows, the '<literal>^Z</literal>' character is interpreted as an
65 end-of-file character, so if you read a file containing this character
66 the file will appear to end just before it. To avoid this,
67 use <literal>IOExts.openFileEx</literal> to open a file in binary
68 (untranslated) mode or change an already opened file handle into
69 binary mode using <literal>IOExts.hSetBinaryMode</literal>. The
70 <literal>IOExts</literal> module is part of the
71 <literal>lang</literal> package.
80 Using GHC (and other GHC-compiled executables) with cygwin</title>
83 <title>Background</title> <para>The cygwin tools aim to provide a
84 unix-style API on top of the windows libraries, to facilitate ports of
85 unix software to windows. To this end, they introduce a unix-style
86 directory hierarchy under some root directory (typically
87 <filename>/</filename> is <filename>C:\cygwin\</filename>). Moreover,
88 everything built against the cygwin API (including the cygwin tools
89 and programs compiled with cygwin's ghc) will see / as the root of
90 their file system, happily pretending to work in a typical unix
91 environment, and finding things like <filename>/bin</filename> and <filename>/usr/include</filename> without
92 ever explicitly bothering with their actual location on the windows
93 system (probably <filename>C:\cygwin\bin</filename> and <filename>C:\cygwin\usr\include</filename>).
97 <sect2><title>The problem</title>
98 <para>GHC, by default, no longer depends on cygwin, but is a native
99 windows program. It is built using mingw, and it uses mingw's ghc
100 while compiling your Haskell sources (even if you call it from
101 cygwin's bash), but what matters here is that - just like any other
102 normal windows program - neither GHC nor the executables it produces
103 are aware of cygwin's pretended unix hierarchy. GHC will happily
104 accept either '/' or '\' as path separators, but it won't know where
105 to find <filename>/home/joe/Main.hs</filename> or <filename>/bin/bash</filename>
106 or the like. This causes all
107 kinds of fun when GHC is used from within cygwin's bash, or in
108 make-sessions running under cygwin.
112 <sect2><title>Things to do</title>
115 <para> Don't use absolute paths in make, configure & co if there is any chance
116 that those might be passed to GHC (or to GHC-compiled programs). Relative
117 paths are fine because cygwin tools are happy with them and GHC accepts
118 '/' as path-separator. And relative paths don't depend on where cygwin's
119 root directory is located, or on which partition or network drive your source
120 tree happens to reside, as long as you 'cd' there first.
124 <para> If you have to use absolute paths (beware of the innocent-looking
125 <literal>ROOT=`pwd`</literal> in makefile hierarchies or configure scripts), cygwin provides
126 a tool called <command>cygpath</command> that can convert cygwin's unix-style paths to their
127 actual windows-style counterparts. Many cygwin tools actually accept
128 absolute windows-style paths (remember, though, that you either need
129 to escape '\' or convert '\' to '/'), so you should be fine just using those
130 everywhere. If you need to use tools that do some kind of path-mangling
131 that depends on unix-style paths (one fun example is trying to interpret ':'
132 as a separator in path lists..), you can still try to convert paths using
133 <command>cygpath</command> just before they are passed to GHC and friends.
137 <para> If you don't have <command>cygpath</command>, you probably don't have cygwin and hence
138 no problems with it... unless you want to write one build process for several
139 platforms. Again, relative paths are your friend, but if you have to use
140 absolute paths, and don't want to use different tools on different platforms,
141 you can simply write a short Haskell program to print the current directory
142 (thanks to George Russell for this idea): compiled with GHC, this will give
143 you the view of the file system that GHC depends on (which will differ
144 depending on whether GHC is compiled with cygwin's gcc or mingw's
145 gcc or on a real unix system..) - that little program can also deal with
146 escaping '\' in paths. Apart from the banner and the startup time,
147 something like this would also do:
149 $ echo "Directory.getCurrentDirectory >>= putStrLn . init . tail . show " | ghci
157 <sect1 id="win32-dlls">
158 <Title>Building and using Win32 DLLs
162 <IndexTerm><Primary>Dynamic link libraries, Win32</Primary></IndexTerm>
163 <IndexTerm><Primary>DLLs, Win32</Primary></IndexTerm>
164 On Win32 platforms, the compiler is capable of both producing and using
165 dynamic link libraries (DLLs) containing ghc-compiled code. This
166 section shows you how to make use of this facility.
170 Until recently, <Command>strip</Command> didn't work reliably on DLLs, so you
171 should test your version with care, or make sure you have the latest
172 binutils. Unfortunately, we don't know exactly which version of binutils
173 cured the problem (it was supposedly fixed some years ago).
177 <Sect2 id="win32-dlls-link">
178 <Title>Linking with DLLs
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
239 <emphasis>Making libraries into DLLs doesn't work on Windows at the
240 moment (and is no longer supported); however, all the machinery is
241 still there. If you're interested, contact the GHC team. Note that
242 building an entire Haskell application as a DLL is still supported
243 (it's just inter-DLL Haskell calls that don't work).</emphasis>
244 <IndexTerm><Primary>Creating a Win32 DLL</Primary></IndexTerm>
245 <IndexTerm><Primary>––mk-dll</Primary></IndexTerm>
246 Sealing up your Haskell library inside a DLL is straightforward;
247 compile up the object files that make up the library, and then build
248 the DLL by issuing a command of the form:
253 ghc ––mk-dll -o foo.dll bar.o baz.o wibble.a -lfooble
258 By feeding the ghc compiler driver the option <Option>––mk-dll</Option>, it
259 will build a DLL rather than produce an executable. The DLL will
260 consist of all the object files and archives given on the command
265 To create a `static' DLL, i.e. one that does not depend on the GHC DLLs,
266 use the <Option>-static</Option> when compiling up your Haskell code and
271 A couple of things to notice:
279 Since DLLs correspond to packages (see <XRef LinkEnd="packages">) you need
280 to use <Option>-package-name dll-name</Option> when compiling modules that
281 belong to a DLL if you're going to call them from Haskell. Otherwise, Haskell
282 code that calls entry points in that DLL will do so incorrectly, and crash.
283 For similar reasons, you can only compile a single module tree into a DLL,
284 as <Function>startupHaskell</Function> needs to be able to call its
285 initialisation function, and only takes one such argument (see <XRef
286 LinkEnd="win32-dlls-foreign">). Hence the modules
287 you compile into a DLL must have a common root.
293 By default, the entry points of all the object files will be exported from
294 the DLL when using <Option>––mk-dll</Option>. Should you want to constrain
295 this, you can specify the <Emphasis>module definition file</Emphasis> to use
296 on the command line as follows:
299 ghc ––mk-dll -o .... -optdll--def -optdllMyDef.def
302 See Microsoft documentation for details, but a module definition file
303 simply lists what entry points you want to export. Here's one that's
304 suitable when building a Haskell COM server DLL:
308 DllCanUnloadNow = DllCanUnloadNow@0
309 DllGetClassObject = DllGetClassObject@12
310 DllRegisterServer = DllRegisterServer@0
311 DllUnregisterServer = DllUnregisterServer@0
318 In addition to creating a DLL, the <Option>––mk-dll</Option> option also
319 creates an import library. The import library name is derived from the
320 name of the DLL, as follows:
323 DLL: HScool.dll ==> import lib: libHScool_imp.a
326 The naming scheme may look a bit weird, but it has the purpose of allowing
327 the co-existence of import libraries with ordinary static libraries (e.g.,
328 <Filename>libHSfoo.a</Filename> and
329 <Filename>libHSfoo_imp.a</Filename>.
331 Additionally, when the compiler driver is linking in non-static mode, it
332 will rewrite occurrence of <Option>-lHSfoo</Option> on the command line to
333 <Option>-lHSfoo_imp</Option>. By doing this for you, switching from
334 non-static to static linking is simply a question of adding
335 <Option>-static</Option> to your command line.
345 <Sect2 id="win32-dlls-foreign">
346 <Title>Making DLLs to be called from other languages</Title>
350 If you want to package up Haskell code to be called from other languages,
351 such as Visual Basic or C++, there are some extra things it is useful to
352 know. The dirty details are in the <Emphasis>Foreign Function
353 Interface</Emphasis> definition, but it can be tricky to work out how to
354 combine this with DLL building, so here's an example:
362 Use <Literal>foreign export</Literal> declarations to export the Haskell
363 functions you want to call from the outside. For example,
368 adder :: Int -> Int -> IO Int -- gratuitous use of IO
369 adder x y = return (x+y)
371 foreign export stdcall adder :: Int -> Int -> IO Int
381 ghc -c adder.hs -fglasgow-exts
384 This will produce two files, adder.o and adder_stub.o
390 compile up a <Function>DllMain()</Function> that starts up the Haskell
391 RTS-––a possible implementation is:
394 #include <windows.h>
395 #include <Rts.h>
397 EXTFUN(__stginit_Adder);
399 static char* args[] = { "ghcDll", NULL };
400 /* N.B. argv arrays must end with NULL */
409 if (reason == DLL_PROCESS_ATTACH) {
410 /* By now, the RTS DLL should have been hoisted in, but we need to start it up. */
411 startupHaskell(1, args, __stginit_Adder);
418 Here, <Literal>Adder</Literal> is the name of the root module in the module
419 tree (as mentioned above, there must be a single root module, and hence a
420 single module tree in the DLL).
435 ghc ––mk-dll -o adder.dll adder.o adder_stub.o dllMain.o
443 Start using <Function>adder</Function> from VBA-––here's how I would
444 <Constant>Declare</Constant> it:
447 Private Declare Function adder Lib "adder.dll" Alias "adder@8"
448 (ByVal x As Long, ByVal y As Long) As Long
451 Since this Haskell DLL depends on a couple of the DLLs that come with GHC,
452 make sure that they are in scope/visible.
456 Building statically linked DLLs is the same as in the previous section: it
457 suffices to add <Option>-static</Option> to the commands used to compile up
458 the Haskell source and build the DLL.
471 ;;; Local Variables: ***
473 ;;; sgml-parent-document: ("users_guide.sgml" "book" "chapter") ***