modification of a global array variable does not succeed, when passed with `mut x` to an initialisation function

[spytheman]

V version: V 0.4.9 f8b70b7, press to see full `v doctor` output

V full version	V 0.4.9 52cd627.f8b70b7
OS	linux, Ubuntu 20.04.6 LTS
Processor	4 cpus, 64bit, little endian, Intel(R) Core(TM) i3-3225 CPU @ 3.30GHz
Memory	0.31GB/15.05GB
V executable	/home/delian/code/v/v
V last modified time	2025-03-06 11:20:58
V home dir	OK, value: /home/delian/code/v
VMODULES	OK, value: /home/delian/.vmodules
VTMP	OK, value: /tmp/v_1000
Current working dir	OK, value: /home/delian/code/v
env VFLAGS	"-no-parallel"
Git version	git version 2.48.1
V git status	weekly.2025.10-21-gf8b70b72
.git/config present	true
cc version	cc (Ubuntu 10.5.0-1ubuntu1~20.04) 10.5.0
gcc version	gcc (Ubuntu 10.5.0-1ubuntu1~20.04) 10.5.0
clang version	clang version 10.0.0-4ubuntu1
tcc version	tcc version 0.9.28rc 2024-07-31 HEAD@1cee0908 (x86_64 Linux)
tcc git status	thirdparty-linux-amd64 0134e9b9
emcc version	N/A
glibc version	ldd (Ubuntu GLIBC 2.31-0ubuntu9.16) 2.31

What did you do?
./v -g -o vdbg cmd/v && ./vdbg x.v && x

@[has_globals]
module main

struct Rectangle {
	x int
	y int
	w int
	h int
}

__global bricks = []Rectangle{}

fn init_bricks(mut bricks []Rectangle) {
	for i in 0..5 {
		bricks << Rectangle{i, 2*i, 3*i, 4*i}		
	}
	dump(bricks.len)
}

fn main() {
	dump(bricks.len)
	init_bricks(mut bricks)
	dump(bricks.len)
}

What did you see?

[x.v:21] bricks.len: 0
[x.v:17] bricks.len: 5
[x.v:23] bricks.len: 0

What did you expect to see?

[x.v:21] bricks.len: 0
[x.v:17] bricks.len: 5
[x.v:23] bricks.len: 5

Note

You can use the 👍 reaction to increase the issue's priority for developers.

Please note that only the 👍 reaction to the issue itself counts as a vote.
Other reactions and those to comments will not be taken into account.

[huly-for-github]

Connected to Huly®: V_0.6-22277

[spytheman]

In other words, init_bricks initializes something that is not the bricks global.

[jorgeluismireles]

Worked for me adding &:

__global bricks = &[]Rectangle{}

[medvednikov]

There's variable shadowing here which shouldn't be allowed. It wouldn't compile if it was a const.

[spytheman]

I can use another name for the parameter, compared to the global variable, and still get a buggy result:

@[has_globals]
module main

struct Rectangle {
    x int
    y int
    w int
    h int
}

__global gbricks = []Rectangle{}

fn init_bricks(mut bricks []Rectangle) {
    for i in 0..5 {
        bricks << Rectangle{i, 2*i, 3*i, 4*i}
    }
    dump(bricks.len)
}

fn main() {
    dump(gbricks.len)
    init_bricks(mut gbricks)
    dump(gbricks.len)
}

produces:

[z.v:21] gbricks.len: 0
[z.v:17] bricks.len: 5
[z.v:23] gbricks.len: 0

[spytheman]

Worked for me adding &:

__global bricks = &[]Rectangle{}

Yes, the issue is specifically, when the global is an array, and not a reference to an array.
The two cases, should both work.