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<p class=MsoNormal>Hi,<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>I am trying to build a very simple Haskell function (foo)
which I can then<o:p></o:p></p>
<p class=MsoNormal>call from C, using an example I got from the GHC FFI Wiki.
The problem is that<o:p></o:p></p>
<p class=MsoNormal>the resulting program fails to run with a seg fault. <o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Here is the code:<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>---Haskell Module start (Foo.hs)<o:p></o:p></p>
<p class=MsoNormal>module Foo where<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>foreign export ccall foo :: Int -> IO Int<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>foo :: Int -> IO Int<o:p></o:p></p>
<p class=MsoNormal>foo n = return (length (f n))<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>f :: Int -> [Int]<o:p></o:p></p>
<p class=MsoNormal>f 0 = []<o:p></o:p></p>
<p class=MsoNormal>f n = n:(f (n-1))<o:p></o:p></p>
<p class=MsoNormal>---Haskell Module end<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>/*- C module start foo.c*/<o:p></o:p></p>
<p class=MsoNormal>#include <stdio.h><o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>#include "Foo_stub.h"<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>int main(void)<o:p></o:p></p>
<p class=MsoNormal>{<o:p></o:p></p>
<p class=MsoNormal> int x = foo(100);<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal> //printf("x = %d\n", x);<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal> return 0;<o:p></o:p></p>
<p class=MsoNormal>}<o:p></o:p></p>
<p class=MsoNormal>/*- C module end */<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>The I build the a.out with the commands:<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>ghc -fglasgow-exts -fffi -c Foo.hs<o:p></o:p></p>
<p class=MsoNormal>ghc -fglasgow-exts -fffi Foo.o Foo_stub.o foo.c<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Now if I run the resulting a.out then I get:<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Segmentation fault<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Quickly putting this through GDB I get:<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>gdb ./a.out <o:p></o:p></p>
<p class=MsoNormal>GNU gdb Red Hat Linux (6.5-16.el5rh)<o:p></o:p></p>
<p class=MsoNormal>Copyright (C) 2006 Free Software Foundation, Inc.<o:p></o:p></p>
<p class=MsoNormal>GDB is free software, covered by the GNU General Public
License, and you are<o:p></o:p></p>
<p class=MsoNormal>welcome to change it and/or distribute copies of it under
certain conditions.<o:p></o:p></p>
<p class=MsoNormal>Type "show copying" to see the conditions.<o:p></o:p></p>
<p class=MsoNormal>There is absolutely no warranty for GDB. Type "show
warranty" for details.<o:p></o:p></p>
<p class=MsoNormal>This GDB was configured as
"i386-redhat-linux-gnu"...<o:p></o:p></p>
<p class=MsoNormal>(no debugging symbols found)<o:p></o:p></p>
<p class=MsoNormal>Using host libthread_db library
"/lib/libthread_db.so.1".<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>run<o:p></o:p></p>
<p class=MsoNormal>Starting program: /home/brg/dev/haskell/ffi/a.out <o:p></o:p></p>
<p class=MsoNormal>(no debugging symbols found)<o:p></o:p></p>
<p class=MsoNormal>(no debugging symbols found)<o:p></o:p></p>
<p class=MsoNormal>(no debugging symbols found)<o:p></o:p></p>
<p class=MsoNormal>[Thread debugging using libthread_db enabled]<o:p></o:p></p>
<p class=MsoNormal>[New Thread 7870144 (LWP 22448)]<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Program received signal SIGSEGV, Segmentation fault.<o:p></o:p></p>
<p class=MsoNormal>[Switching to Thread 7870144 (LWP 22448)]<o:p></o:p></p>
<p class=MsoNormal>0x0805c313 in allocateLocal ()<o:p></o:p></p>
<p class=MsoNormal>(gdb) where<o:p></o:p></p>
<p class=MsoNormal>#0 0x0805c313 in allocateLocal ()<o:p></o:p></p>
<p class=MsoNormal>#1 0x0000005c in ?? ()<o:p></o:p></p>
<p class=MsoNormal>#2 0x08075c97 in base_DataziTypeable_zdLr42klvl4_srt ()<o:p></o:p></p>
<p class=MsoNormal>#3 0x4ee1dca0 in _dl_argv_internal () from
/lib/ld-linux.so.2<o:p></o:p></p>
<p class=MsoNormal>#4 0x0807c920 in last_free_capability ()<o:p></o:p></p>
<p class=MsoNormal>#5 0x4ee1dca0 in _dl_argv_internal () from
/lib/ld-linux.so.2<o:p></o:p></p>
<p class=MsoNormal>#6 0x00000000 in ?? ()<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>I am using GHC 6.6.1 built from sources on RHE5.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Many regards,<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Ben<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><b><span
style='color:navy'>Benedict R. Gaster</span></b><br>
<span style='font-size:8.0pt;font-family:"Arial","sans-serif";color:navy'>S/W
Architecture Team Lead<br>
ClearSpeed Technology Plc</span><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:navy'><br>
</span><span style='font-size:8.0pt;font-family:"Arial","sans-serif";
color:navy'>3110 Great Western Court <br>
Hunts Ground Road</span><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:navy'><br>
</span><span style='font-size:8.0pt;font-family:"Arial","sans-serif";
color:navy'>Stoke Gifford </span><span style='font-size:10.0pt;font-family:
"Arial","sans-serif";color:navy'><br>
</span><span style='font-size:8.0pt;font-family:"Arial","sans-serif";
color:navy'>Bristol </span><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:navy'><br>
</span><span style='font-size:8.0pt;font-family:"Arial","sans-serif";
color:navy'>BS34 8HP<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:8.0pt;font-family:"Arial","sans-serif";
color:navy'><a href="blocked::mailto:karen@clearspeed.com"
title="blocked::mailto:karen@clearspeed.com mailto:lamont@clearspeed.com mailto:helena@clearspeed.com"><span
style='color:navy;text-decoration:none'>Phone:</span></a> + 44 117 3172016<br>
Fax: + 44 117 3172002</span><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:navy'><br>
</span><span style='font-size:8.0pt;font-family:"Arial","sans-serif";
color:navy'><a href="mailto:brg@clearspeed.com"
title="blocked::mailto:karen@clearspeed.com mailto:lamont@clearspeed.com mailto:helena@clearspeed.com"><span
style='color:blue'>brg@clearspeed.com</span></a><br>
<a href="blocked::blocked::blocked::http://www.clearspeed.com"
title="blocked::blocked::blocked::http://www.clearspeed.com blocked::http://www.clearspeed.com http://www.clearspeed.com"><span
style='color:blue'>www.clearspeed.com</span></a></span><o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
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<p class=MsoNormal>-- <o:p></o:p></p>
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Hunts Ground Road, Bristol BS34 8HP, UK. <o:p></o:p></span></p>
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<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
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href="http://www.clearspeed.com/aboutus/company/index.html"
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