Address review: test the parsed path, skip custom page size, tidy

Author: rustyconover

src/lib/libdylink.js

@@ -295,7 +295,10 @@ var LibraryDylink = {
       // Detect immutable wasm global exports. These represent data addresses
       // which are relative to `memoryBase`.  `mutableGlobals`, when known,
       // saves probing each global.
-      if (mutableGlobals ? value instanceof WebAssembly.Global && !mutableGlobals.has(name) : isImmutableGlobal(value)) {
+      var immutable = mutableGlobals
+        ? value instanceof WebAssembly.Global && !mutableGlobals.has(name)
+        : isImmutableGlobal(value);
+      if (immutable) {
         return new WebAssembly.Global({'value': '{{{ POINTER_WASM_TYPE }}}'}, value.value + {{{ to64('memoryBase') }}});
       }
 
@@ -496,8 +499,9 @@ var LibraryDylink = {
 
       function skipLimits() {
         var flags = getU8();
-        getLEB();
-        if (flags & 1) getLEB();
+        getLEB(); // min
+        if (flags & 1) getLEB(); // max
+        if (flags & 8) getLEB(); // page size (custom-page-sizes)
       }
 
       while (offset < binary.length) {
@@ -525,7 +529,7 @@ var LibraryDylink = {
               if (op === 0x43) offset += 4; // f32.const
               else if (op === 0x44) offset += 8; // f64.const
               // i32.const, i64.const, global.get, ref.null, ref.func
-              else if ([0x41, 0x42, 0x23, 0xd0, 0xd2].includes(op)) getLEB();
+              else if (op === 0x41 || op === 0x42 || op === 0x23 || op === 0xd0 || op === 0xd2) getLEB();
               // Anything but the extended-const add, sub and mul instructions
               else if (!(op >= 0x6a && op <= 0x6c || op >= 0x7c && op <= 0x7e)) return;
             }

test/test_other.py

@@ -7340,6 +7340,12 @@ def test_dlopen_exported_globals(self):
         assert(side_data && side_data == side_data_addr());
         assert(*side_data == 42);
         EM_ASM({
+          // The loader read the mutable globals from the binary, rather than
+          // falling back to probing each one.
+          var metadata = getDylinkMetadata(new Uint8Array(require('fs').readFileSync('libside.wasm')));
+          assert(metadata.mutableGlobals, 'mutableGlobals not parsed');
+          assert(metadata.mutableGlobals.size == 1 && metadata.mutableGlobals.has('side_global'));
+
           var g = LDSO.loadedLibsByHandle[$0].exports['side_global'];
           assert(g instanceof WebAssembly.Global);
           g.value = 7;