How can i set the imported memory to accept shared memory in clang

K0IN

Hi I want to do a simple WASM multi thread test(in c), but I cannot get shared memory to work. I'm using plain clang. This is what I tried so far
Compiled with:

clang++ src/*.cpp -Oz -c -Wall --target=wasm32 -fvisibility=hidden -pthread 
wasm-ld *.o --no-entry --allow-undefined --strip-all --export-dynamic --import-memory --import-table -o test.wasm

JavaScript memory declaration:

const memory = new WebAssembly.Memory( { initial: memory_init_pages,shared: true, maximum:64} );	//

error MSG:

LinkError: WebAssembly Instantiation: mismatch in shared state of memory, declared = 0, imported = 1

my c++ programm just writes to memory at a given address and check if it worked

admin

@K0IN Glad to hear!

K0IN

Never mind (solved it) got it to work you need to set the link flag "--shared-memory"

"C:/Program Files/LLVM/bin/wasm-ld" *.o --no-entry --allow-undefined --strip-all --export-dynamic --import-memory --shared-memory --import-table --strip-debug --max-memory=1310720 -o test.wasm

also, you need to set --max-memory

my test project is available at https://github.com/K0IN/WebassemblySimpleMultithreading

K0IN

main.cpp

 __attribute__((visibility("default"))) extern "C" int set( int adr, int value) {	
	*(int*)adr = value;
  	return *(int*)adr;
}

Clang emits:

(module
  (type $t0 (func (param i32 i32) (result i32)))
  (import "env" "memory" (memory $env.memory 2))
  (import "env" "__indirect_function_table" (table $env.__indirect_function_table 1 anyfunc))
  (func $set (type $t0) (param $p0 i32) (param $p1 i32) (result i32)
    get_local $p0
    get_local $p1
    i32.store
    get_local $p1)
  (global $g0 (mut i32) (i32.const 66560))
  (global $__heap_base i32 (i32.const 66560))
  (global $__data_end i32 (i32.const 1024))
  (export "__heap_base" (global 1))
  (export "__data_end" (global 2))
  (export "set" (func $set)))

according to https://github.com/WebAssembly/threads/blob/master/proposals/threads/Overview.md
the memory type should be "shared" but isn't how can I enable that (is there a link flag for that?)

What i want to do:
In the main thread I write to __heap_base + 10 (an exported variable by clang) just some random values and in the worker I want to do the same on __heap_base + 14 I do the same and later check in js if the memory changed

The program works on single thread but I cannot load shared memory.

(also yes I enabled sharedarraybuffer in chrome)

Becavalier

Can you please show me your c/c++ source code?