Dereferenced pointer to struct doesn't copy #30

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opened 2025-08-31 19:36:08 +00:00 by snorlax · 3 comments

snorlax commented

2025-08-31 19:36:08 +00:00

import io

Point {
	x int
}

Point(x int) -> *Point {
	p := new(Point)
	p.x = x
	return p
}

main() {
	p := Point(1)
	write(p)
}

write(p *Point) {
	io.write("Point: ")
	p2 := [p]
	p2.x = 999
	io.write(p2.x)
	io.write("\nPoint: ")
	io.write(p.x)
}

output:
q.exe examples\point\
Point: 999
Point: 999

I expect the struct to be copied when pointer is dereferenced similar to: https://godbolt.org/z/TE3GMaY77

``` import io Point { x int } Point(x int) -> *Point { p := new(Point) p.x = x return p } main() { p := Point(1) write(p) } write(p *Point) { io.write("Point: ") p2 := [p] p2.x = 999 io.write(p2.x) io.write("\nPoint: ") io.write(p.x) } output: q.exe examples\point\ Point: 999 Point: 999 ``` I expect the struct to be copied when pointer is dereferenced similar to: https://godbolt.org/z/TE3GMaY77

👍 1

ed added the

bug

label

2025-08-31 20:38:27 +00:00

ed self-assigned this

2025-08-31 20:38:28 +00:00

ed commented

2025-09-01 18:48:44 +00:00

Owner

Hi snorlax, thanks for the report!

I took a look at the --ssa --func main.write debug output from the compiler.
The dereferencing doesn't show up in the output, instead it just copied the value like p2 := p.
I will check which part of the parser caused the incorrect compilation.

Just a heads up, this could take quite a bit of time to fix.

Edit:

Parsing bug fixed in cli/q@6b3a26a80a.
Temporary "not implemented" message added in cli/q@87207b4191.

Hi snorlax, thanks for the report! I took a look at the `--ssa --func main.write` debug output from the compiler. The dereferencing doesn't show up in the output, instead it just copied the value like `p2 := p`. I will check which part of the parser caused the incorrect compilation. Just a heads up, this could take quite a bit of time to fix. --- *Edit:* Parsing bug fixed in https://git.urbach.dev/cli/q/commit/6b3a26a80ae5de6a3c01586a2fbce359b320004c. Temporary "not implemented" message added in https://git.urbach.dev/cli/q/commit/87207b41918bf26a62860c40262bb33c7a6be91b.

👍 1

ed added spent time

2025-09-01 19:51:16 +00:00

1 hour

ed commented

2025-09-06 15:57:57 +00:00

Owner

Fixed in cli/q@76cd1cf419.

It will currently attempt to load every field from the struct into a local register.
This obviously needs some polishing, but at least the code you provided now prints the correct values.

Test: cli/q@76cd1cf419/tests/struct-pointer-deref.q

Fixed in https://git.urbach.dev/cli/q/commit/76cd1cf419ff4f2ce8b53815e5bbf31d55c1e049. It will currently attempt to load every field from the struct into a local register. This obviously needs some polishing, but at least the code you provided now prints the correct values. Test: https://git.urbach.dev/cli/q/src/commit/76cd1cf419ff4f2ce8b53815e5bbf31d55c1e049/tests/struct-pointer-deref.q

ed added spent time

2025-09-06 15:58:19 +00:00

1 hour

ed commented

2025-09-09 09:54:34 +00:00

Owner

Closing this one because the provided code sample works now.
If you notice more code examples that don't have the desired output feel free to open new issues!

Closing this one because the provided code sample works now. If you notice more code examples that don't have the desired output feel free to open new issues!

ed closed this issue

2025-09-09 09:54:34 +00:00