| Re: CALL_EXTERNAL Problems with IDL [message #40446 is a reply to message #40305] |
Wed, 04 August 2004 04:35  |
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Bob[2]
Messages: 5
Registered: June 2004
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Junior Member |
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Peter, I am not sure where that -7 comes from, but it does show you are
talented. ;) A few comments on your query.
You want to make a "shared library" for call_external. Shared libraries
come up with different names on different platforms, a vocabulary
nuisance. On Linux, there are some compile flags to set. Take a look
at your documentation. Also,
http://www.fortran-2000.com/ArnaudRecipes/sharedlib.html
is handy for sorting out terminology. I use gcc to compile my source
files and than I usually use ld to build a shared library.
Another thing you might want to do is include the IDL header file,
idl_export.h, which is somewhere in your IDL files. E.g., in one of my
C programs, I have
#include "/Applications/idl_6.0/external/include/idl_export.h"
So your 'int' type has to be switched to 'IDL_INT' -- though 'double' is
OK as is. I have noticed that on my system (OS-X,Darwin), I have to
leave the main() function as type 'int' or the compiler chokes. There
is probably a flag to set in gcc that will allow 'IDL_INT main( void )'
but I have not dug it out.
Third: one thing I noticed a while ago is that when you are running
idlde and testing your .so shareable object, you have to reset the IDL
session after you modify and recompile the .so because IDL still has the
previous .so loaded. Just a guess, but this might be where that sweet
value of -7 comes from. There are some postings on this reset trick in
the newsgroup a few months ago.
Stay working on it, and reading the Linux documentation.
- Thomas
PeterOut wrote:
> I am using IDL Version 6.0 (linux x86 m32) on Red Hat Linux release 9.
>
> I have been trying to get CALL_EXTERNAL to do *something* for me so I
> wrote some very simple code, Generic.c, which follows. I also define
> the functions in Generic.h.
> ------------------------------------------------------------ -------------
> #include <stdio.h>
> #include <stdlib.h>
> #include "Generic.h"
>
> int Simple()
> {
> return 16;
> }
>
> int PowerOf2()
> {
> int output;
> output=32;
> return output;
> }
> ------------------------------------------------------------ -------------
> I then compile this code with
>
>> gcc -c Generic.c -o Generic.o
>
> and confirm that the functions are there thus.
>
>> nm Generic.o
>
> 0000000a T PowerOf2
> 00000000 T Simple
>
> This is what I now get on IDL.
> IDL> print,call_external('/home/me/Generic.o','Simple',/i_value)
> % CALL_EXTERNAL: Error loading sharable executable.
> Symbol: Simple, File = /home/me/Generic.o
> /usr/local/rsi/idl_6.0/bin/bin.linux.x86/libidl.so.6.0:
> undefined symbol: Simple
>
> IDL> print,call_external('/home/me/Generic.o','PowerOf2',/i_value )
> 0
> IDL> print,call_external('/home/me/Generic.o','PowerOf2',/i_value )
> -7
>
> OK. So how is Simple undefined?
> And how does it get 0 and then 7 from 32?
>
> Many thanks in advance for any help,
> Peter.
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