Binary format: Don't emit empty Memory sections (#5145)

If the only memories are imported, we don't need the section. We were already
doing that for tables, functions, etc.

3 files changed, 12 insertions, 2 deletions

diff --git a/test/unit/input/only-imported-memory.wasm b/test/unit/input/only-imported-memory.wasm
new file mode 100644
index 000000000..175113e10
--- /dev/null
+++ b/test/unit/input/only-imported-memory.wasm
diff --git a/test/unit/test_only_imported_memory.py b/test/unit/test_only_imported_memory.py
new file mode 100644
index 000000000..427f464d0
--- /dev/null
+++ b/test/unit/test_only_imported_memory.py
@@ -0,0 +1,8 @@
+from . import utils
+
+
+class OnlyImportedMemoryTest(utils.BinaryenTestCase):
+    def test_only_imported_memory(self):
+        # We should not create a memories section for a file with only an
+        # imported memory: such a module has no declared memories.
+        self.roundtrip('only-imported-memory.wasm', debug=False)
diff --git a/test/unit/utils.py b/test/unit/utils.py
index b75ed311c..b0391afad 100644
--- a/test/unit/utils.py
+++ b/test/unit/utils.py
@@ -9,9 +9,11 @@ class BinaryenTestCase(unittest.TestCase):
         return os.path.join(shared.options.binaryen_test, 'unit', 'input',
                             filename)
 
-    def roundtrip(self, filename, opts=[]):
+    def roundtrip(self, filename, opts=[], debug=True):
+        if debug:
+            opts = opts + ['-g']
         path = self.input_path(filename)
-        p = shared.run_process(shared.WASM_OPT + ['-g', '-o', 'a.wasm', path] +
+        p = shared.run_process(shared.WASM_OPT + ['-o', 'a.wasm', path] +
                                opts)
         self.assertEqual(p.returncode, 0)
         with open(path, 'rb') as f: