From 72ea3c030a81262af64ebcae2e83ce2ff529bcef Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C5=81ukasz=20Langa?= <lukasz@langa.pl>
Date: Mon, 24 Feb 2025 00:26:04 +0100
Subject: [PATCH] gh-128627: Skip wasm-gc on iOS Safari where it's broken
 (#130418)

As of iOS 18.3.1, enabling wasm-gc breaks the interpreter. This disables the wasm-gc
trampoline on iOS.

Co-authored-by: Hood Chatham <roberthoodchatham@gmail.com>
---
 Python/emscripten_trampoline.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/Python/emscripten_trampoline.c b/Python/emscripten_trampoline.c
index 0293c7ea0f3..a7bb685bf3d 100644
--- a/Python/emscripten_trampoline.c
+++ b/Python/emscripten_trampoline.c
@@ -77,7 +77,13 @@ EM_JS(CountArgsFunc, _PyEM_GetCountArgsPtr, (), {
 //         i32.const -1
 //     )
 // )
-addOnPreRun(() => {
+
+function getPyEMCountArgsPtr() {
+    let isIOS = globalThis.navigator && /iPad|iPhone|iPod/.test(navigator.platform);
+    if (isIOS) {
+        return 0;
+    }
+
     // Try to initialize countArgsFunc
     const code = new Uint8Array([
         0x00, 0x61, 0x73, 0x6d, // \0asm magic number
@@ -149,15 +155,19 @@ addOnPreRun(() => {
             0x41, 0x7f,       // i32.const -1
             0x0b // end function
     ]);
-    let ptr = 0;
     try {
         const mod = new WebAssembly.Module(code);
         const inst = new WebAssembly.Instance(mod, { e: { t: wasmTable } });
-        ptr = addFunction(inst.exports.f);
+        return addFunction(inst.exports.f);
     } catch (e) {
         // If something goes wrong, we'll null out _PyEM_CountFuncParams and fall
         // back to the JS trampoline.
+        return 0;
     }
+}
+
+addOnPreRun(() => {
+    const ptr = getPyEMCountArgsPtr();
     Module._PyEM_CountArgsPtr = ptr;
     const offset = HEAP32[__PyEM_EMSCRIPTEN_COUNT_ARGS_OFFSET / 4];
     HEAP32[(__PyRuntime + offset) / 4] = ptr;