| Re: Global variables and command line [message #11547] |
Tue, 21 April 1998 00:00  |
steinhh
Messages: 260
Registered: June 1994
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Senior Member |
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J.D.Smith wrote:
[..snip..]
> At the risk of being too arcane here, I think Daniel's point is quite a
> valid one, and his problem less easily solved than it might at first
> glance seem. Sometimes, one wants to access variables from the $MAIN$
> level in a routine, and sometimes one wants to put variables created
> inside a routine into $MAIN$. You might wonder what circumstance could
> exist that would require this functionality. I would simply then direct
> you to RSI's own Insight, in which after getting in you have the option
> of "Select Data to Import"..."IDL Variables"... with a list of $MAIN$
> level variables displayed. Now clearly the folks at RSI have convenient
> access to the names and data locations of the $MAIN$ level variables,
> and I think they should give us mere ordinary users that access also.
[..snip..]
> I am henceforth considering submitting an enhancement request for a
> function that will provide the names and data locations (e.g. through
> pointers) of $MAIN$ level variables inside routines, and the ability to
> create $MAIN$ level variables from within routines, in a safe form.
[..snip..]
> Perhaps RSI is trying to protect us from ourselves here, realizing that
> with the problems people have with variable locality already, breaking
> it slightly might serve to confuse even more. But they really shouldn't
> underestimate our ability to harness and control whatever new power
> comes our way. And besides, if they get to do it, then so should we.
I agree.
In an attempt to nominate myself for the 'IDL Hacker of the year'
award :-) I dug into something that I'd seen while programming RPC
calls to IDL ... and ended up wasting a days work on this thing that
doesn't seem to work, even though I think it *should* work;
Below is a set of C routines that need to be compiled and linked into
shareable libraries (and remember to include the "libidl" shareable
library in the linking... on my alpha that's done by adding e.g.,
"-L$IDL_DIR/bin/bin.alpha -lidl" to the linker statement). The
easiest way to find the (other) correct compile/link flags is
to modify the $IDL_DIR/external/sharelib/Makefile to include your
file.
The getmain() function is added as a System Routine (very neat - at
least I learned *this* from my little exercise!), but it doesn't
work as expected:
IDL> print,CALL_EXTERNAL('gmain.so','addmain') ;; Install routine
1
IDL> print,getmain('ADF')
% GETMAIN: Couldn't find variable ; As expected
% Execution halted at: $MAIN$
IDL> adf=1
IDL> print,getmain('ADF')
Main name ADF, at 140033a58
Main variable type/flag: 2 0
Copying:
Returning: 2 2
1 ; So far, so good...
IDL> .r
- pro test
- print,getmain('ADF')
- end
% Compiled module: TEST.
IDL> test
Main name ADF, at 140033c98 ; <- address is wrong, but not NULL!
Main variable type/flag: 0 0
Copying:
Returning: 0 2
% PRINT: Variable is undefined: <UNDEFINED>.
% Execution halted at: TEST 2 /dev/tty
% $MAIN$
So, does anyone know what's going wrong here...? Does it behave like
this for all platforms...?
Regards,
Stein Vidar
C source follows (void for non-nerds.. :-)
------------------------------------------------------------ --gmain.c
#include <stdio.h>
#include "export.h"
#include <strings.h>
/*
Initialize with:
print,CALL_EXTERNAL('gmain.so','addmain')
then, you *should* be able to get the value of a non-dynamic
main-level variable with:
print,getmain('<VARNAME>')
Alas, this only works from the $MAIN$ scope - which is a bit
silly....
*/
#define NULL_VPTR ((IDL_VPTR) NULL)
IDL_VPTR getmain(int argc, IDL_VPTR argv[])
{
IDL_VPTR main_variable;
IDL_VPTR retv;
IDL_VPTR main_name;
retv = IDL_Gettmp();
main_name = argv[0];
IDL_ENSURE_STRING(main_name);
IDL_ENSURE_SCALAR(main_name);
main_variable = IDL_GetVarAddr(main_name->value.str.s);
if (main_variable == NULL_VPTR) {
IDL_Message(IDL_M_NAMED_GENERIC,IDL_MSG_LONGJMP,"Couldn't find variable");
}
printf("Main name %s, at %lx\n\r",main_name->value.str.s,main_variable);
printf("Main variable type/flag: %d %d\n\r",(int)main_variable->type,
(int)main_variable->flags);
if ( ! (main_variable->flags & IDL_V_DYNAMIC) ) {
fprintf(stderr,"Copying: \n\r");
bcopy(main_variable,retv,sizeof(*retv));
retv->flags |= IDL_V_TEMP;
}
fprintf(stderr,"Returning: %d %d\n\r",retv->type,retv->flags);
return retv;
}
IDL_SYSFUN_DEF main_def[] = { {(IDL_FUN_RET) getmain, "GETMAIN", 1, 1} };
IDL_LONG addmain(int argc,char *argv[])
{
int tmp;
/* I haven't the faintest idea whether or not this statement is required,
or whether it's completely out of line... */
tmp=IDL_Init(0,&argc,argv);
/* This one was neat, though: */
IDL_AddSystemRoutine(main_def,IDL_TRUE,1); /* Just add getmain... */
return tmp;
}
------------------------------------------------------------ ----------
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