add test

Author: dschuff

test/test_other.py

@@ -10265,6 +10265,30 @@ def test_wasm_features_section(self, args):
     self.run_process([EMCC, test_file('hello_world.c'), '-O2'] + args)
     self.verify_custom_sec_existence('a.out.wasm', 'target_features', False)
 
+  def test_wasm_features(self):
+    # Test that wasm features are explicitly enabled or disabled based on target engine version
+    def verify_features_sec(feature, expect_in):
+      with webassembly.Module('hello_world.o') as module:
+        features = module.get_target_features()
+      if expect_in:
+        self.assertTrue(feature in features and features[feature] == webassembly.TargetFeaturePrefix.USED)
+      else:
+        self.assertFalse(feature in features)
+
+    def compile(flag):
+      self.run_process([EMCC, test_file('hello_world.c'), '-c', flag])
+
+    compile('')
+    verify_features_sec('bulk-memory', False)
+    verify_features_sec('nontrapping-fptoint', False)
+    verify_features_sec('sign-ext', True)
+    verify_features_sec('mutable-globals', True)
+    verify_features_sec('multivalue', True)
+
+    compile('-sMIN_SAFARI_VERSION=150000')
+    verify_features_sec('bulk-memory', True)
+    verify_features_sec('nontrapping-fptoint', True)
+
   def test_js_preprocess(self):
     # Use stderr rather than stdout here because stdout is redirected to the output JS file itself.
     create_file('lib.js', '''

tools/webassembly.py

@@ -162,6 +162,12 @@ class DylinkType(IntEnum):
   IMPORT_INFO = 4
 
 
+class TargetFeaturePrefix(IntEnum):
+  USED = 0x2b
+  DISALLOWED = 0x2d
+  REQUIRED = 0x3d
+
+
 class InvalidWasmError(BaseException):
   pass
 
@@ -561,6 +567,18 @@ def get_function_type(self, idx):
       func_type = self.get_function_types()[idx - self.num_imported_funcs()]
     return self.get_types()[func_type]
 
+  def get_target_features(self):
+    section = self.get_custom_section('target_features')
+    self.seek(section.offset)
+    assert self.read_string() == 'target_features'
+    features = {}
+    feature_count = self.read_byte()
+    while self.tell() < section.offset + section.size:
+      prefix = TargetFeaturePrefix(self.read_byte())
+      feature = self.read_string()
+      features[feature] = prefix
+    return features
+
 
 def parse_dylink_section(wasm_file):
   with Module(wasm_file) as module: