Android aarch64 build with Luau JIT fails due to missing `__clear_cache` symbol

[rafaelqcc]

Building mlua with Luau JIT enabled fails on Android/aarch64 because the linker cannot resolve the __clear_cache symbol required by Luau's JIT code allocator.

Environment

• Android aarch64
• Termux
• Rust target: aarch64-linux-android
• mlua features:

mlua = { version = "0.12.0", features = ["luau", "luau-jit", "vendored"] }

Error

During linking:

ld.lld: error: undefined symbol: __clear_cache

referenced by CodeAllocator.cpp
flushInstructionCache(unsigned char*, unsigned long)

The error happens inside Luau JIT code:

luau/CodeGen/src/CodeAllocator.cpp

Tested versions

mlua 0.11.6

Dependencies:

mlua-sys 0.10.0
luau0-src 0.18.3+luau709

The build can succeed after adding a manual __clear_cache stub, but Luau JIT execution can trigger a SIGTRAP.

mlua 0.12.0

Dependencies:

mlua-sys 0.11.0
luau0-src 0.20.7+luau728

The same missing symbol happens during linking.

Workaround

Adding a manual stub allows the linker to continue:

#[unsafe(no_mangle)]
pub extern "C" fn __clear_cache(
    _begin: *mut u8,
    _end: *mut u8,
) {
}

However, this is only a workaround and may not be the correct solution for JIT instruction cache invalidation.

Expected behavior

mlua with luau-jit should build successfully on Android/aarch64 without requiring users to manually define __clear_cache.

Additional information

The same Luau JIT configuration works on other platforms where __clear_cache is available.

It appears that the Android/aarch64 build needs a proper implementation or compatibility handling for instruction cache flushing when using Luau JIT.