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<p class=MsoNormal><font size=2 color=blue face=Verdana><span style='font-size:
10.0pt;font-family:Verdana;color:blue'>There’s been a bit of traffic
about calling Haskell from C++ recently, and I know that calling C++ from
Haskell is a frequently asked question. (E.g. Koen Claessen was asking me about
it this week.) It also seems to be somewhat platform dependent.
(Esp on Windows, I think.)<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=blue face=Verdana><span style='font-size:
10.0pt;font-family:Verdana;color:blue'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=blue face=Verdana><span style='font-size:
10.0pt;font-family:Verdana;color:blue'> Would
someone like to write up a description of how <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=blue face=Verdana><span style='font-size:
10.0pt;font-family:Verdana;color:blue'> to
successfully call out from Haskell to C++ and vice versa, <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=blue face=Verdana><span style='font-size:
10.0pt;font-family:Verdana;color:blue'> using
GHC? <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=blue face=Verdana><span style='font-size:
10.0pt;font-family:Verdana;color:blue'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=blue face=Verdana><span style='font-size:
10.0pt;font-family:Verdana;color:blue'>If you did, we’d gladly include the
result in the user manual, and save others a lot of head scratching. Maybe
there are simple things we could do to GHC to make the process simpler.
But what it needs is someone who knows C++ well to write a coherent story.
Please!<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=blue face=Verdana><span style='font-size:
10.0pt;font-family:Verdana;color:blue'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=blue face=Verdana><span style='font-size:
10.0pt;font-family:Verdana;color:blue'>Simon<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=blue face=Verdana><span style='font-size:
10.0pt;font-family:Verdana;color:blue'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=blue face=Verdana><span style='font-size:
10.0pt;font-family:Verdana;color:blue'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span lang=EN-US
style='font-size:10.0pt;font-family:Tahoma;font-weight:bold'>From:</span></font></b><font
size=2 face=Tahoma><span lang=EN-US style='font-size:10.0pt;font-family:Tahoma'>
glasgow-haskell-users-bounces@haskell.org
[mailto:glasgow-haskell-users-bounces@haskell.org] <b><span style='font-weight:
bold'>On Behalf Of </span></b>Rich Neswold<br>
<b><span style='font-weight:bold'>Sent:</span></b> 13 September 2005 16:45<br>
<b><span style='font-weight:bold'>To:</span></b> Felix Breuer<br>
<b><span style='font-weight:bold'>Cc:</span></b>
glasgow-haskell-users@haskell.org<br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: FFI: calling Haskell
from C++?</span></font><span lang=EN-US><o:p></o:p></span></p>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>On 9/13/05, <b><span style='font-weight:bold'>Felix Breuer</span></b>
<<a href="mailto:felix@fbreuer.de">felix@fbreuer.de</a>> wrote:<o:p></o:p></span></font></p>
<div>
<blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0cm 0cm 0cm 6.0pt;
margin-left:4.8pt;margin-right:0cm'>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> $ ghc -fffi Foo.o Foo_stub.o main.cpp<br>
main.o(.text+0x22): In function `main':<br>
main.cpp: undefined reference to `__stginit_Foo()'<br>
main.o(.eh_frame+0x11): undefined reference to
`__gxx_personality_v0'<br>
collect2: ld returned 1 exit status <o:p></o:p></span></font></p>
</blockquote>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><br>
In main.cpp, you need to define __stginit_Foo(void) like this:<br>
<br>
extern "C" void __stginit_Foo(void);<br clear=all>
<br>
Specifying the "C" linkage with prevent the compiler from looking for
a name-mangled version of the function.<br>
<br>
To fix the second problem, you need to shut off exception handling (specifying
the -fno-exceptions option ought to do this. I don't know how to pass compiler
option via ghc, though.<br>
<br>
-- <br>
Rich<br>
<br>
AIM : rnezzy<br>
ICQ : 174908475 <o:p></o:p></span></font></p>
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