| Re: CALL_EXTERNAL Problems with IDL [message #40434 is a reply to message #40305] |
Wed, 04 August 2004 13:36   |
MajorSetback
Messages: 9
Registered: August 2004
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Junior Member |
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I noticed that you addressed both the issues I raised in my follow-up.
My mistake. I guess I paraphrased your replies.
Thanks again,
Peter.
Bob <jipnoji@janet-reno.com> wrote in message news:<LR3Qc.26314$iK.3208@newsread2.news.atl.earthlink.net>...
> 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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