This would've made a good Stack Overflow question.
Another technique that can be used in cases like this is to declare the
extern C function as taking a 'ref' argument:
testit.chpl
-----------
record R {
var x: int;
}
require "testit.h";
extern proc foo(ref x: int);
var myR = new R(42);
foo(myR.x);
writeln(myR);
testit.h
--------
void foo(int64_t* x);
testit.c
--------
#include <stdio.h>
#include <stdint.h>
#include "testit.h"
void foo(int64_t* x) {
printf("Got %lld\n", *x);
*x += 1;
}
On Tue, 15 Aug 2017, Aji, Ashwin wrote:
I figured that this was a bug in my code, so I did not open a bug report in
Chapel.
Regards,
Ashwin
-----Original Message-----
From: Michael Ferguson [mailto:[email protected]]
Sent: Wednesday, August 02, 2017 7:56 AM
To: Aji, Ashwin <[email protected]>
Cc: [email protected]
Subject: Re: [Chapel-developers] Reference to a record/class field in Chapel
Hi -
I think c_ptrTo(a_obj.value) ought to work. I think this is a bug. Can file a
bug report with a simple reproducer?
Thanks,
-michael
Hi,
In Chapel, how can I pass a reference (c pointer style) to a field of a
record/class to an external C function.
For example,
extern proc c_func(val_ptr: c_void_ptr);
class A {
type retType;
var value: retType;
// constructors not shown but they are the usual simple ones }
proc foo() {
var a_obj = A;
c_func(c_ptrTo(a_obj.value));
// codegen first creates a copy of a_obj and then passes pointer to
the copy¹s value field.
// A a_obj_copy = a_obj; // copy by value
// c_func(&(c_obj_copy.value));
// But, I want the below:
// c_func(&(c_obj.value));
}
Regards,
Ashwin
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