From 8c0d524fcbdab525192703fe120df76f28151957 Mon Sep 17 00:00:00 2001
From: Sam Clegg <sbc@chromium.org>
Date: Mon, 8 Sep 2025 12:35:53 -0700
Subject: [PATCH] Remove global `currentModuleWeakSymbols` from dynamic linking
 code

Using a global has led to at least one bug: #25214
---
 src/lib/libdylink.js                          | 20 +++++++++----------
 src/preamble.js                               |  7 +++++--
 test/codesize/test_codesize_hello_dylink.json |  8 ++++----
 .../test_codesize_hello_dylink_all.json       |  4 ++--
 4 files changed, 21 insertions(+), 18 deletions(-)

diff --git a/src/lib/libdylink.js b/src/lib/libdylink.js
index 50020af24a7fc..87f8ea2ee1371 100644
--- a/src/lib/libdylink.js
+++ b/src/lib/libdylink.js
@@ -164,14 +164,15 @@ var LibraryDylink = {
   },
 
   $GOT: {},
-  $currentModuleWeakSymbols: '=new Set({{{ JSON.stringify(Array.from(WEAK_IMPORTS)) }}})',
 
-  // Create globals to each imported symbol.  These are all initialized to zero
-  // and get assigned later in `updateGOT`
+  // Proxy handler used for GOT.mem and GOT.func imports.  Each of these
+  // imports is fullfilled dynamically via the `get` method of this proxy
+  // handler.  We abuse the `target` of the Proxy in order to pass the set of
+  // weak imports to the handler.
   $GOTHandler__internal: true,
-  $GOTHandler__deps: ['$GOT', '$currentModuleWeakSymbols'],
+  $GOTHandler__deps: ['$GOT'],
   $GOTHandler: {
-    get(obj, symName) {
+    get(weakImports, symName) {
       var rtn = GOT[symName];
       if (!rtn) {
 #if DYLINK_DEBUG == 2
@@ -179,7 +180,7 @@ var LibraryDylink = {
 #endif
         rtn = GOT[symName] = new WebAssembly.Global({'value': '{{{ POINTER_WASM_TYPE }}}', 'mutable': true}, {{{ UNDEFINED_ADDR }}});
       }
-      if (!currentModuleWeakSymbols.has(symName)) {
+      if (!weakImports.has(symName)) {
         // Any non-weak reference to a symbol marks it as `required`, which
         // enabled `reportUndefinedSymbols` to report undefined symbol errors
         // correctly.
@@ -660,7 +661,6 @@ var LibraryDylink = {
     '$loadDynamicLibrary', '$getMemory', '$updateGOT',
     '$relocateExports', '$resolveGlobalSymbol', '$GOTHandler',
     '$getDylinkMetadata', '$alignMemory',
-    '$currentModuleWeakSymbols',
     '$updateTableMap',
     '$wasmTable',
     '$addOnPostCtor',
@@ -799,10 +799,10 @@ var LibraryDylink = {
         }
       };
       var proxy = new Proxy({}, proxyHandler);
-      currentModuleWeakSymbols = metadata.weakImports;
+      var GOTProxy = new Proxy(metadata.weakImports, GOTHandler);
       var info = {
-        'GOT.mem': new Proxy({}, GOTHandler),
-        'GOT.func': new Proxy({}, GOTHandler),
+        'GOT.mem': GOTProxy,
+        'GOT.func': GOTProxy,
         'env': proxy,
         '{{{ WASI_MODULE_NAME }}}': proxy,
       };
diff --git a/src/preamble.js b/src/preamble.js
index 2b09f06f615b9..c54ec203849bc 100644
--- a/src/preamble.js
+++ b/src/preamble.js
@@ -684,6 +684,9 @@ function getWasmImports() {
 #endif
 #endif
   // prepare imports
+#if MAIN_MODULE || RELOCATABLE
+  var GOTProxyHandler = new Proxy(new Set({{{ JSON.stringify(Array.from(WEAK_IMPORTS)) }}}), GOTHandler);
+#endif
   var imports = {
 #if MINIFY_WASM_IMPORTED_MODULES
     'a': wasmImports,
@@ -692,8 +695,8 @@ function getWasmImports() {
     '{{{ WASI_MODULE_NAME }}}': wasmImports,
 #endif // MINIFY_WASM_IMPORTED_MODULES
 #if MAIN_MODULE || RELOCATABLE
-    'GOT.mem': new Proxy(wasmImports, GOTHandler),
-    'GOT.func': new Proxy(wasmImports, GOTHandler),
+    'GOT.mem': GOTProxyHandler,
+    'GOT.func': GOTProxyHandler,
 #endif
   };
 #if SPLIT_MODULE
diff --git a/test/codesize/test_codesize_hello_dylink.json b/test/codesize/test_codesize_hello_dylink.json
index fc8649404fd3b..565c180431299 100644
--- a/test/codesize/test_codesize_hello_dylink.json
+++ b/test/codesize/test_codesize_hello_dylink.json
@@ -1,10 +1,10 @@
 {
-  "a.out.js": 26552,
-  "a.out.js.gz": 11345,
+  "a.out.js": 26546,
+  "a.out.js.gz": 11349,
   "a.out.nodebug.wasm": 17761,
   "a.out.nodebug.wasm.gz": 9003,
-  "total": 44313,
-  "total_gz": 20348,
+  "total": 44307,
+  "total_gz": 20352,
   "sent": [
     "__syscall_stat64",
     "emscripten_resize_heap",
diff --git a/test/codesize/test_codesize_hello_dylink_all.json b/test/codesize/test_codesize_hello_dylink_all.json
index 09de86abc7a59..0c2e7110427d1 100644
--- a/test/codesize/test_codesize_hello_dylink_all.json
+++ b/test/codesize/test_codesize_hello_dylink_all.json
@@ -1,7 +1,7 @@
 {
-  "a.out.js": 245483,
+  "a.out.js": 245475,
   "a.out.nodebug.wasm": 573783,
-  "total": 819266,
+  "total": 819258,
   "sent": [
     "IMG_Init",
     "IMG_Load",