nativesizeof routine returns the different result from sizeof function in C when it takes a CArray object as an argument.

[p6rt]

Migrated from rt.perl.org#129240 (status was 'open')

Searchable as RT129240$

[p6rt]

From @titsuki

See the following result

$ perl6 -MNativeCall -e 'my $null = Pointer; my $not-null = CArray[int32].new; $not-null[0] = 1; $not-null[1] = 1; $not-null[2] = 1; say nativesizeof($not-null)' 8

I think that it should return 12, since the following equivalent C code returns 12.

--

#include \<stdio.h>

int main() {   int a[3];   a[0] = 1;   a[1] = 1;   a[2] = 1;   printf("sizeof a​: %d\n", sizeof(a)); // sizeof a​: 12 }

--

$ gcc --version gcc (Debian 4.9.2-10) 4.9.2 Copyright (C) 2014 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ perl6 --version This is Rakudo version 2016.07.1-199-gdd9b760 built on MoarVM version 2016.07-17-g40948f6 implementing Perl 6.c.

[p6rt]

From @geekosaur

On Sat, Sep 10, 2016 at 10​:11 AM, Itsuki Toyota \< perl6-bugs-followup@​perl.org> wrote​:

$ perl6 -MNativeCall -e 'my $null = Pointer; my $not-null = CArray[int32].new; $not-null[0] = 1; $not-null[1] = 1; $not-null[2] = 1; say nativesizeof($not-null)' 8

That size looks doubly wrong to me. Its not going to happen for a 3-element array no matter how you slice it... so I suspect you're getting the size of one element, which is itself twice the size of what C thinks.

-- brandon s allbery kf8nh sine nomine associates allbery.b@​gmail.com ballbery@​sinenomine.net unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net

[p6rt]

The RT System itself - Status changed from 'new' to 'open'

[p6rt]

From @FROGGS

You get 8 there because an array is a pointerish thing...

Btw, this​:   my $not-null = CArray[int32].new is not the same as this​:   int a[3];

So, we would need fixed sized native arrays here to tell the truth.

Am 10.09.2016 um 20​:53 schrieb Brandon Allbery via RT​:

On Sat, Sep 10, 2016 at 10​:11 AM, Itsuki Toyota \< perl6-bugs-followup@​perl.org> wrote​:

$ perl6 -MNativeCall -e 'my $null = Pointer; my $not-null = CArray[int32].new; $not-null[0] = 1; $not-null[1] = 1; $not-null[2] = 1; say nativesizeof($not-null)' 8

That size looks doubly wrong to me. Its not going to happen for a 3-element array no matter how you slice it... so I suspect you're getting the size of one element, which is itself twice the size of what C thinks.