Only export user-requests symbols on the Module object. NFC

Some exports are only needed internally and those don't need to be
exported on the Module object.  This is save some space and avoids
unexpected exports on the public-facing Module.

Author: sbc100

emscripten.py

@@ -799,6 +799,15 @@ def make_export_wrappers(exports, delay_assignment):
     if name == '__cpp_exception':
       continue
     mangled = asmjs_mangle(name)
+    # We only export onto the Module object of the user requested the export.
+    # Some exports are used internally by library functions and don't need to be
+    # publically exported.
+    # The exception is `dynCall_` functions, which are dynamically used via the
+    # Module object (see dynCallLegacy in library.js).
+    if mangled in building.user_requested_exports or name.startswith('dynCall_'):
+      lhs = f'{mangled} = Module["{mangled}"]'
+    else:
+      lhs = f'{mangled}'
     # The emscripten stack functions are called very early (by writeStackCookie) before
     # the runtime is initialized so we can't create these wrappers that check for
     # runtimeInitialized.
@@ -808,27 +817,27 @@ def make_export_wrappers(exports, delay_assignment):
       if delay_assignment:
         wrappers.append('''\
 /** @type {function(...*):?} */
-var %(mangled)s = Module["%(mangled)s"] = createExportWrapper("%(name)s");
-''' % {'mangled': mangled, 'name': name})
+var %(lhs)s = createExportWrapper("%(name)s");
+''' % {'lhs': lhs, 'name': name})
       else:
         wrappers.append('''\
 /** @type {function(...*):?} */
-var %(mangled)s = Module["%(mangled)s"] = createExportWrapper("%(name)s", asm);
-''' % {'mangled': mangled, 'name': name})
+var %(lhs)s = createExportWrapper("%(name)s", asm);
+''' % {'lhs': lhs, 'name': name})
     elif delay_assignment:
       # With assertions disabled the wrapper will replace the global var and Module var on
       # first use.
       wrappers.append('''\
 /** @type {function(...*):?} */
-var %(mangled)s = Module["%(mangled)s"] = function() {
-  return (%(mangled)s = Module["%(mangled)s"] = Module["asm"]["%(name)s"]).apply(null, arguments);
+var %(lhs)s = function() {
+  return (%(lhs)s = Module["asm"]["%(name)s"]).apply(null, arguments);
 };
-''' % {'mangled': mangled, 'name': name})
+''' % {'lhs': lhs, 'name': name})
     else:
       wrappers.append('''\
 /** @type {function(...*):?} */
-var %(mangled)s = Module["%(mangled)s"] = asm["%(name)s"]
-''' % {'mangled': mangled, 'name': name})
+var %(lhs)s = asm["%(name)s"]
+''' % {'lhs': lhs, 'name': name})
   return wrappers
 
 

tests/code_size/random_printf_wasm.json

@@ -1,6 +1,6 @@
 {
-  "a.html": 12854,
-  "a.html.gz": 6948,
-  "total": 12854,
-  "total_gz": 6948
+  "a.html": 12862,
+  "a.html.gz": 6952,
+  "total": 12862,
+  "total_gz": 6952
 }

tests/code_size/random_printf_wasm2js.json

@@ -1,6 +1,6 @@
 {
-  "a.html": 17360,
-  "a.html.gz": 7495,
-  "total": 17360,
-  "total_gz": 7495
+  "a.html": 17362,
+  "a.html.gz": 7499,
+  "total": 17362,
+  "total_gz": 7499
 }

tests/other/metadce/test_metadce_cxx_ctors1.jssize

@@ -1 +1 @@
-26202
+25730

tests/other/metadce/test_metadce_cxx_ctors2.jssize

@@ -1 +1 @@
-26166
+25694

tests/other/metadce/test_metadce_cxx_except.jssize

@@ -1 +1 @@
-31595
+31079

tests/other/metadce/test_metadce_cxx_except_wasm.jssize

@@ -1 +1 @@
-26356
+25708

tests/other/metadce/test_metadce_cxx_mangle.jssize

@@ -1 +1 @@
-31695
+31079

tests/other/metadce/test_metadce_cxx_noexcept.jssize

@@ -1 +1 @@
-26202
+25730

tests/other/metadce/test_metadce_hello_O0.jssize

@@ -1 +1 @@
-26698
+26111