mac: Checking for existence of a key in a map using the 'in' keyword causes a segfault

[tomialagbe]

V doctor:

V full version: V 0.4.7 e560553.1085f45
OS: macos, macOS, 14.5, 23F79
Processor: 10 cpus, 64bit, little endian, Apple M1 Pro

getwd: /Users/tomialagbe/dev-projects
vexe: /Users/tomialagbe/v/v
vexe mtime: 2024-08-27 10:35:08

vroot: OK, value: /Users/tomialagbe/v
VMODULES: OK, value: /Users/tomialagbe/.vmodules
VTMP: OK, value: /tmp/v_501

Git version: git version 2.39.3 (Apple Git-146)
Git vroot status: weekly.2024.34-48-g1085f458
.git/config present: true

CC version: Apple clang version 15.0.0 (clang-1500.3.9.4)
thirdparty/tcc status: thirdparty-macos-arm64 713692d4

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

module main

pub struct EventBus[T] {
mut:
	subscribers map[string][]Subscriber[T]
}

type EventType = string
type Subscriber[T] = fn (T)

pub fn new_event_bus[T]() &EventBus[T] {
	return &EventBus[T]{
		subscribers: map[string][]Subscriber[T]{}
	}
}

fn (shared eb EventBus[T]) subscribe(event_type EventType, subscriber Subscriber[T]) {
	lock eb {
		if event_type !in eb.subscribers {
			eb.subscribers[event_type] = []Subscriber[T]{}
		}
		
		eb.subscribers[event_type] << subscriber
	}
}

fn (shared eb EventBus[T]) publish(event_type EventType, data T) {
	lock eb {
		for _, subscriber in eb.subscribers[event_type] {
			subscriber(data)
		}
	}
}

fn main() {
	mut eb := new_event_bus[string]()
	eb.subscribe('test', fn (data string) {
		println(data)
	})
	eb.publish('test', 'hello')
}

What did you expect to see?

hello

What did you see instead?

signal 11: segmentation fault
0   libsystem_platform.dylib            0x000000018a02b584 _sigtramp + 56
1   event_bus_trial                     0x0000000104fa02cc map_key_to_index + 36
2   event_bus_trial                     0x0000000104f883a4 map_exists + 32
3   event_bus_trial                     0x0000000104fc7dcc main__EventBus_T_string_subscribe_T_string + 112
4   event_bus_trial                     0x0000000104fc8070 main__main + 84
5   event_bus_trial                     0x0000000104fc8760 main + 84
6   dyld                                0x0000000189c720e0 start + 2360

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[JalonSolov]

I cannot reproduce the problem on my Linux machine. How did you trigger it? When I run the program after compiling as shown, it just hangs until I hit Ctrl-C:

[jalon@7950x v]$ ./v -g -o vdbg cmd/v && ./vdbg event_bus_trial.v
[jalon@7950x v]$ ./event_bus_trial
^C
[jalon@7950x v]$

[spytheman]

It is reproducible on macos:
0[15:17:22]@m1: (master) /opt/v $ v -cc clang run ee.v
signal 11: segmentation fault
0 libsystem_platform.dylib 0x00000001805af584 _sigtramp + 56
1 ee 0x00000001045542cc map_key_to_index + 36
2 ee 0x000000010453c3a4 map_exists + 32
3 ee 0x000000010457bdcc main__EventBus_T_string_subscribe_T_string + 112
4 ee 0x000000010457c070 main__main + 84
5 ee 0x000000010457c760 main + 84
6 dyld 0x00000001801f60e0 start + 2360
139[15:17:34]@m1: (master) /opt/v $

[yuyi98]

mut eb := new_event_bus[string]()
It's wrong to use it here.
We should use shared eb := new_event_bus[string]().

[spytheman]

mut eb := new_event_bus[string]() It's wrong to use it here. We should use shared eb := new_event_bus[string]().

That is right.
I think we should add a checker error, for mut eb, used for methods with shared receivers.

struct Abc { x int }
fn f(shared a Abc) { lock a { println(a.x) } }
fn (shared a Abc) m(){ lock a { println(a.x) } }
// mut a := Abc{}
// f(a) // checker error

mut b := Abc{} // if b is not mutable, there is a checker error, telling the user to declare `b` with `mut` to make it mutable; the message can be changed too, to mention that it should be `shared` too
b.m() // no checker error, but it is better to have one, similar to the `f(a)` case above

[yuyi98]

Yes, we should add a checker error.

[medvednikov]

I've removed shared receivers from V. Passing tests, will be live soon.

[medvednikov]

(as discussed on discord)