Re: Inline::C and NULL pointers

Here's a little program illustrating one way of using undef as a 'NULL pointer' parameter in Inline C.

use strict;
use warnings;

my $point = pack 'f2', 1.2, 2.3;
func(\$point); 
func(undef);   # pass in 'NULL pointer' 

use Inline C => <<'C_END';

typedef struct { float x, y; } Point;

void func(SV *buf) {
    SV *point_ref = SvRV(buf);
    
    if (!point_ref) {
        printf("got a null pointer\n");
    }
    else {
        /* dereference */
        Point *point = (Point *)SvPV_nolen(point_ref);
        printf("x=%.2f, y=%.2f\n", point->x, point->y);
    }
}

C_END
[download]

Hope this helps.

Comment on Re: Inline::C and NULL pointers Download Code

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Re^2: Inline::C and NULL pointers by etj (Priest) on Dec 19, 2021 at 15:37 UTC
Rather than requiring passing a reference, it would be better to just pass a normal scalar and use `SvOK` to see if it is defined rather than what looks a bit contrived with the `SvRV`. As it is, your code does not handle the case of a non-ref value.	[reply] [d/l] [select]
Re^3: Inline::C and NULL pointers by Chrysotoxum (Novice) on Dec 19, 2021 at 22:09 UTC
Just updated the program to take on board your helpful critique. `use strict; use warnings; my $point = pack 'f2', 1.2, 2.3; func(undef); # pass in 'NULL pointer' func($pointer); Inline C => <<'C_END'; typedef struct { float x, y; } Point; void func(SV buf) { if (!SvOK(buf)) { printf("got a null pointer\n"); } else if (SvPOK(buf) && SvCUR(BUF) == sizeof(Point)) { Point point = (Point *)SvPV_nolen(buf); printf("x=%.2f, y=%.2f\n"); } else { croak("invalid scalar"); } } C_END` [download]	[reply] [d/l]
Re^4: Inline::C and NULL pointers by etj (Priest) on Dec 27, 2021 at 08:42 UTC
Sorry to only just notice this (and thanks for the kind words)! I think your `printf` line needs two more args, `point[0], point[1]`?	[reply] [d/l] [select]