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Author: hoodmane

Makefile.pre.in

@@ -3118,7 +3118,7 @@ Python/emscripten_trampoline_inner.wasm: $(srcdir)/Python/emscripten_trampoline_
 	$$(dirname $$(dirname $(CC)))/bin/clang -o $@ $< -mgc -O2 -Wl,--no-entry -Wl,--import-table -Wl,--import-memory -target wasm32-unknown-unknown -nostdlib
 
 Python/emscripten_trampoline_wasm.c: Python/emscripten_trampoline_inner.wasm
-	$(PYTHON_FOR_REGEN) $(srcdir)/Tools/wasm/emscripten/prepare_wat.py $< $@ getWasmTrampolineModule
+	$(PYTHON_FOR_REGEN) $(srcdir)/Tools/wasm/emscripten/prepare_external_wasm.py $< $@ getWasmTrampolineModule
 
 Python/emscripten_trampoline_wasm.o: Python/emscripten_trampoline_wasm.c
 	$(CC) -c $(PY_CORE_CFLAGS) -o $@ $<

Python/emscripten_trampoline.c

@@ -3,30 +3,44 @@
 #include <emscripten.h>             // EM_JS, EM_JS_DEPS
 #include <Python.h>
 
-// We have to be careful to work correctly with memory snapshots. Even if we are
-// loading a memory snapshot, we need to perform the JS initialization work.
-// That means we can't call the initialization code from C. Instead, we export
-// this function pointer to JS and then fill it in a preRun function which runs
-// unconditionally.
-/**
- * Backwards compatible trampoline works with all JS runtimes
- */
 EM_JS(
 PyObject*,
 _PyEM_TrampolineCall_inner, (int* success,
                              PyCFunctionWithKeywords func,
                              PyObject *arg1,
                              PyObject *arg2,
                              PyObject *arg3), {
+    // JavaScript fallback trampoline
     return wasmTable.get(func)(arg1, arg2, arg3);
 }
-try {
-  const trampolineModule = getWasmTrampolineModule();
-  const trampolineInstance = new WebAssembly.Instance(trampolineModule, {
-    env: { __indirect_function_table: wasmTable, memory: wasmMemory },
-  });
-  _PyEM_TrampolineCall_inner = trampolineInstance.exports.trampoline_call;
-} catch (e) {}
+// Try to replace the JS definition of _PyEM_TrampolineCall_inner with a wasm
+// version.
+(function () {
+    // iOS ships broken wasm-gc, so feature detect and turn it off
+    const isIOS =
+        globalThis.navigator &&
+        (/iPad|iPhone|iPod/.test(navigator.userAgent) ||
+            // Starting with iPadOS 13, iPads might send a platform string that looks like a desktop Mac.
+            // To differentiate, we check if the platform is 'MacIntel' (common for Macs and newer iPads)
+            // AND if the device has multi-touch capabilities (navigator.maxTouchPoints > 1)
+            (navigator.platform === "MacIntel" &&
+                typeof navigator.maxTouchPoints !== "undefined" &&
+                navigator.maxTouchPoints > 1));
+    if (isIOS) {
+        return;
+    }
+    try {
+        const trampolineModule = getWasmTrampolineModule();
+        const trampolineInstance = new WebAssembly.Instance(trampolineModule, {
+            env: { __indirect_function_table: wasmTable, memory: wasmMemory },
+        });
+        _PyEM_TrampolineCall_inner = trampolineInstance.exports.trampoline_call;
+        console.log("Assigned _PyEM_TrampolineCall_inner!");
+    } catch (e) {
+        // Compilation error due to missing wasm-gc support, fall back to JS
+        // trampoline
+    }
+})();
 );
 
 PyObject*

Python/emscripten_trampoline_inner.c

@@ -1,3 +1,8 @@
+// This file must be compiled with -mgc to enable the extra wasm-gc
+// instructions. It has to be compiled separately because not enough JS runtimes
+// support wasm-gc yet. If the JS runtime does not support wasm-gc (or has buggy
+// support like iOS), we will use the JS trampoline fallback.
+
 typedef void PyObject;
 
 typedef PyObject* (*three_arg)(PyObject*, PyObject*, PyObject*);

Tools/wasm/emscripten/prepare_wat.py renamed to Tools/wasm/emscripten/prepare_external_wasm.py

@@ -3,7 +3,6 @@
 import argparse
 import sys
 from pathlib import Path
-from shutil import which
 
 JS_TEMPLATE = """
 #include "emscripten.h"
@@ -20,22 +19,7 @@
 }});
 """
 
-
-def find_wasm_as():
-    emcc_path = which("emcc")
-    if not emcc_path:
-        print("Error: emcc not found in PATH", file=sys.stderr)
-        return None
-
-    wasm_as_path = Path(emcc_path).parents[1] / "bin/wasm-as"
-
-    if not wasm_as_path.exists():
-        print(f"Error: wasm-as not found at {wasm_as_path}", file=sys.stderr)
-        return None
-    return wasm_as_path
-
-
-def compile_wat(input_file, output_file, function_name):
+def prepare_wasm(input_file, output_file, function_name):
     # Read the compiled WASM as binary and convert to hex
     wasm_bytes = Path(input_file).read_bytes()
 
@@ -63,7 +47,7 @@ def main():
 
     args = parser.parse_args()
 
-    return compile_wat(args.input_file, args.output_file, args.function_name)
+    return prepare_wasm(args.input_file, args.output_file, args.function_name)
 
 
 if __name__ == "__main__":