Commit 0760b84e authored by Edward Z. Yang's avatar Edward Z. Yang Committed by Austin Seipp
Browse files

Update foreign export docs, fixes #10467

Signed-off-by: default avatarEdward Z. Yang <>

Reviewed By: rwbarton, austin

Differential Revision:

GHC Trac Issues: #10467
parent f0636562
......@@ -271,16 +271,12 @@ void hs_thread_done(void);
<para>When GHC compiles a module (say <filename>M.hs</filename>)
which uses <literal>foreign export</literal> or
<literal>foreign import "wrapper"</literal>, it generates two
additional files, <filename>M_stub.c</filename> and
<filename>M_stub.h</filename>. GHC will automatically compile
<filename>M_stub.c</filename> to generate
<filename>M_stub.o</filename> at the same time.</para>
<literal>foreign import "wrapper"</literal>, it generates
a <filename>M_stub.h</filename> for use by C programs.</para>
<para>For a plain <literal>foreign export</literal>, the file
<filename>M_stub.h</filename> contains a C prototype for the
foreign exported function, and <filename>M_stub.c</filename>
contains its definition. For example, if we compile the
foreign exported function. For example, if we compile the
following module:</para>
......@@ -302,23 +298,14 @@ f n = n:(f (n-1))</programlisting>
#include "HsFFI.h"
extern HsInt foo(HsInt a0);</programlisting>
<para>and <filename>Foo_stub.c</filename> contains the
compiler-generated definition of <literal>foo()</literal>. To
invoke <literal>foo()</literal> from C, just <literal>#include
<para>To invoke <literal>foo()</literal> from C, just <literal>#include
"Foo_stub.h"</literal> and call <literal>foo()</literal>.</para>
<para>The <filename>foo_stub.c</filename> and
<filename>foo_stub.h</filename> files can be redirected using the
<filename>Foo_stub.h</filename> file can be redirected using the
<option>-stubdir</option> option; see <xref linkend="options-output"
<para>When linking the program, remember to include
<filename>M_stub.o</filename> in the final link command line, or
you'll get link errors for the missing function(s) (this isn't
necessary when building your program with <literal>ghc
--make</literal>, as GHC will automatically link in the
correct bits).</para>
<sect3 id="using-own-main">
<title>Using your own <literal>main()</literal></title>
......@@ -338,7 +325,7 @@ extern HsInt foo(HsInt a0);</programlisting>
#include "HsFFI.h"
#include "foo_stub.h"
#include "Foo_stub.h"
int main(int argc, char *argv[])
......@@ -411,7 +398,7 @@ int main(int argc, char *argv[])
#include "HsFFI.h"
#include "foo_stub.h"
#include "Foo_stub.h"
#include "Rts.h"
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