Run more of out tests with -sNO_DEFAULT_TO_CXX

We were previously only applying this flag to tests that use
`self.build` (i.e. most test).  Now we apply it to and even larger set.

The code size changes here only occur in debug builds where we enumerate
all known JS symbols, and there are come JS symbols are the C++ only.

Author: sbc100

test/common.py

@@ -833,6 +833,11 @@ def setUp(self):
     self.js_engines = config.JS_ENGINES.copy()
     self.settings_mods = {}
     self.emcc_args = ['-Wclosure', '-Werror', '-Wno-limited-postlink-optimizations']
+    # TODO(https://github.com/emscripten-core/emscripten/issues/11121)
+    # For historical reasons emcc compiles and links as C++ by default.
+    # However we want to run our tests in a more strict manner.  We can
+    # remove this if the issue above is ever fixed.
+    self.set_setting('NO_DEFAULT_TO_CXX')
     self.ldflags = []
     # Increate stack trace limit to maximise usefulness of test failure reports
     self.node_args = ['--stack-trace-limit=50']
@@ -954,9 +959,13 @@ def has_changed_setting(self, key):
   def clear_setting(self, key):
     self.settings_mods.pop(key, None)
 
-  def serialize_settings(self):
+  def serialize_settings(self, ldflags=True):
     ret = []
+    # Incomplete list of link-only settings
+    link_only_settings = ['NO_DEFAULT_TO_CXX']
     for key, value in self.settings_mods.items():
+      if not ldflags and key in link_only_settings:
+        continue
       if value == 1:
         ret.append(f'-s{key}')
       elif type(value) is list:
@@ -994,7 +1003,7 @@ def get_emcc_args(self, main_file=False, ldflags=True):
     def is_ldflag(f):
       return any(f.startswith(s) for s in ['-sENVIRONMENT=', '--pre-js=', '--post-js='])
 
-    args = self.serialize_settings() + self.emcc_args
+    args = self.serialize_settings(ldflags) + self.emcc_args
     if ldflags:
       args += self.ldflags
     else:
@@ -1034,12 +1043,6 @@ def build(self, filename, libraries=None, includes=None, force_c=False, js_outfi
       filename = test_file(filename)
     suffix = '.js' if js_outfile else '.wasm'
     compiler = [compiler_for(filename, force_c)]
-    if compiler[0] == EMCC:
-      # TODO(https://github.com/emscripten-core/emscripten/issues/11121)
-      # For historical reasons emcc compiles and links as C++ by default.
-      # However we want to run our tests in a more strict manner.  We can
-      # remove this if the issue above is ever fixed.
-      compiler.append('-sNO_DEFAULT_TO_CXX')
 
     if force_c:
       assert shared.suffix(filename) != '.c', 'force_c is not needed for source files ending in .c'

test/other/metadce/test_metadce_hello_O0.gzsize

@@ -1 +1 @@
-8422
+8391

test/other/metadce/test_metadce_hello_O0.jssize

@@ -1 +1 @@
-23089
+23004

test/other/metadce/test_metadce_minimal_O0.gzsize

@@ -1 +1 @@
-7251
+7218

test/other/metadce/test_metadce_minimal_O0.jssize

@@ -1 +1 @@
-19713
+19628