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Re: CALL_EXTERNAL simple problem ? [message #28067 is a reply to message #27975]

Thu, 15 November 2001 06:51

Randall Skelton
Messages: 169
Registered: October 2000

Senior Member

On 15 Nov 2001, trouble wrote:

[snip]

> Yes - this works! It seems that IDL (on my platform only?) needs C
> functions to have the (argc,*agrv[]) form, despite examples in the
> manual to the contrary. However, now I understand.

Glad it works... but which manuals are you using? All platforms I can
think of would require such a construct to pass IDL variables into C.
Moreover, all of the examples I can find in chapter 7 of the IDL 5.3
External Development Guide (EDG) show the C routines to have the form:

function_name (int argc, void* argv[])

where:

'argc' is the argument counter (i.e. the number of arguments including the
name of the call itself)

'argv' is the argument vector which is an array of pointers to the passed
IDL variables, which are accessible via argv[0] ... argv[argc-1]. Note
that argv has one additional element, argv[argc] which is always a null
pointer. You should be very careful to appropriately define your C
variables so they match the size/structure of the internal IDL variables
(defined in export.h). If you have a mismatch in the size of your
variables, you will corrupt your IDL session.

The real 'root' of the (argc, argv) construction likely arises from the
way that a stand-alone C/Fortran program accept simple command-line
arguments.

Cheers,
Randall

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[Message index]

		Re: CALL_EXTERNAL simple problem ? By: Randall Skelton on Wed, 14 November 2001 05:17
		Re: CALL_EXTERNAL simple problem ? By: the_cacc on Thu, 15 November 2001 04:58
		Re: CALL_EXTERNAL simple problem ? By: Randall Skelton on Thu, 15 November 2001 06:51

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