Enable threads under node when running cmake checks (#15590)

Author: shanumante-sc

emcmake.py

@@ -35,7 +35,10 @@ def has_substr(args, substr):
 
   if not has_substr(args, '-DCMAKE_CROSSCOMPILING_EMULATOR'):
     node_js = config.NODE_JS[0]
-    args.append(f'-DCMAKE_CROSSCOMPILING_EMULATOR={node_js}')
+    # In order to allow cmake to run code built with pthreads we need to pass some extra flags to node.
+    # Note that we also need --experimental-wasm-bulk-memory which is true by default and hence not added here
+    # See https://github.com/emscripten-core/emscripten/issues/15522
+    args.append(f'-DCMAKE_CROSSCOMPILING_EMULATOR={node_js};--experimental-wasm-threads')
 
   # On Windows specify MinGW Makefiles or ninja if we have them and no other
   # toolchain was specified, to keep CMake from pulling in a native Visual

tests/test_other.py

@@ -721,6 +721,10 @@ def test_cmake_static_lib(self, custom):
     else:
       self.assertTrue(building.is_ar('libstatic_lib.a'))
 
+  # Tests that cmake functions which require evaluation via the node runtime run properly with pthreads
+  def test_cmake_pthreads(self):
+    self.run_process([EMCMAKE, 'cmake', '-DCMAKE_C_FLAGS=-pthread', test_file('cmake/target_js')])
+
   # Tests that the CMake variable EMSCRIPTEN_VERSION is properly provided to user CMake scripts
   def test_cmake_emscripten_version(self):
     self.run_process([EMCMAKE, 'cmake', test_file('cmake/emscripten_version')])