Fix emscripten_current_thread_is_wasm_worker return value. (#23484)

This function return `ENVIRONMENT_IS_WASM_WORKER` which was being
initialized to `Module['$ww']`, i.e. the worker id.

Because `emscripten_current_thread_is_wasm_worker`, is defined to return
the `bool` type its only valid values are 0 and 1. Returning values
larger than 1 will result in undefined behaviour.

Fixes: #23479

Author: sbc100

src/shell.js

@@ -122,7 +122,7 @@ if (ENVIRONMENT_IS_NODE) {
 #endif // ENVIRONMENT_MAY_BE_NODE
 
 #if WASM_WORKERS
-var ENVIRONMENT_IS_WASM_WORKER = Module['$ww'];
+var ENVIRONMENT_IS_WASM_WORKER = !!Module['$ww'];
 #endif
 
 // --pre-jses are emitted after the Module integration code, so that they can

src/shell_minimal.js

@@ -70,7 +70,7 @@ var ENVIRONMENT_IS_WEB = !ENVIRONMENT_IS_NODE;
 #endif // ASSERTIONS || PTHREADS
 
 #if WASM_WORKERS
-var ENVIRONMENT_IS_WASM_WORKER = Module['$ww'];
+var ENVIRONMENT_IS_WASM_WORKER = !!Module['$ww'];
 #endif
 
 #if ASSERTIONS && ENVIRONMENT_MAY_BE_NODE && ENVIRONMENT_MAY_BE_SHELL

test/code_size/hello_wasm_worker_wasm.js

@@ -1,4 +1,4 @@
-var b = Module, c = b.$ww, e = b.mem || new WebAssembly.Memory({
+var b = Module, c = !!b.$ww, e = b.mem || new WebAssembly.Memory({
     initial: 256,
     maximum: 256,
     shared: !0

test/code_size/hello_wasm_worker_wasm.json

@@ -1,12 +1,12 @@
 {
   "a.html": 618,
   "a.html.gz": 384,
-  "a.js": 665,
-  "a.js.gz": 455,
+  "a.js": 667,
+  "a.js.gz": 457,
   "a.ww.js": 115,
   "a.ww.js.gz": 127,
   "a.wasm": 1881,
   "a.wasm.gz": 1068,
-  "total": 3279,
-  "total_gz": 2034
+  "total": 3281,
+  "total_gz": 2036
 }

test/wasm_worker/wasm_worker_self_id.c

@@ -17,6 +17,7 @@ void test_success() {
 }
 
 void worker1_main() {
+  assert(emscripten_current_thread_is_wasm_worker());
   assert(emscripten_wasm_worker_self_id() != 0);
   assert(emscripten_wasm_worker_self_id() == worker1);
   if (emscripten_wasm_worker_self_id() == worker1) {
@@ -25,6 +26,7 @@ void worker1_main() {
 }
 
 void worker2_main() {
+  assert(emscripten_current_thread_is_wasm_worker());
   assert(emscripten_wasm_worker_self_id() != 0);
   assert(emscripten_wasm_worker_self_id() == worker2);
   if (emscripten_wasm_worker_self_id() == worker2) {
@@ -36,6 +38,7 @@ char stack1[1024];
 char stack2[1024];
 
 int main() {
+  assert(!emscripten_current_thread_is_wasm_worker());
   assert(emscripten_wasm_worker_self_id() == 0);
   worker1 = emscripten_create_wasm_worker(stack1, sizeof(stack1));
   worker2 = emscripten_create_wasm_worker(stack2, sizeof(stack2));