Support externref in EM_JS functions with dynamic linking (#20171)

Author: hoodmane

emscripten.py

@@ -620,6 +620,7 @@ def type_to_sig(type):
     webassembly.Type.I64: 'j',
     webassembly.Type.F32: 'f',
     webassembly.Type.F64: 'd',
+    webassembly.Type.EXTERNREF: 'e',
     webassembly.Type.VOID: 'v'
   }[type]
 

src/library_addfunction.js

@@ -29,6 +29,7 @@ addToLibrary({
       'j': 'i64',
       'f': 'f32',
       'd': 'f64',
+      'e': 'externref',
 #if MEMORY64
       'p': 'i64',
 #else

test/core/test_externref_emjs.c

@@ -0,0 +1,22 @@
+#include "emscripten/em_js.h"
+
+
+EM_JS(__externref_t, get_ref, (), {
+    return {a: 7, b: 9};
+});
+
+EM_JS(void, modify_ref, (__externref_t arg), {
+    arg.a += 3;
+    arg.b -= 3;
+});
+
+EM_JS(void, log_ref, (__externref_t arg), {
+    console.log(arg);
+});
+
+int main() {
+    __externref_t a = get_ref();
+    log_ref(a);
+    modify_ref(a);
+    log_ref(a);
+}

test/core/test_externref_emjs.out

@@ -0,0 +1,2 @@
+{ a: 7, b: 9 }
+{ a: 10, b: 6 }

test/test_core.py

@@ -9801,6 +9801,19 @@ def test_externref(self):
     self.emcc_args += ['-mreference-types']
     self.do_core_test('test_externref.c', libraries=['asm.o'])
 
+  @parameterized({
+    '': [False],
+    'dynlink': [True]
+  })
+  @requires_node
+  @no_wasm2js('wasm2js does not support reference types')
+  def test_externref_emjs(self, dynlink):
+    self.emcc_args += ['-mreference-types']
+    self.node_args += shared.node_reference_types_flags()
+    if dynlink:
+      self.set_setting('MAIN_MODULE', 2)
+    self.do_core_test('test_externref_emjs.c')
+
   def test_syscall_intercept(self):
     self.do_core_test('test_syscall_intercept.c')
 

tools/shared.py

@@ -356,6 +356,15 @@ def node_bigint_flags():
     return []
 
 
+def node_reference_types_flags():
+  node_version = check_node_version()
+  # reference types were enabled by default in node v18.
+  if node_version and node_version < (18, 0, 0):
+    return ['--experimental-wasm-reftypes']
+  else:
+    return []
+
+
 def node_memory64_flags():
   return ['--experimental-wasm-memory64']