libunwind is broken in Android API levels under 29 without --no-rosegment linker flag (ARM backtraces)

[lassade]

Hi, I counldn't make stacktraces work with arm, even worse the native android crash dump backtrace are pointing at the worng place.
While debuging using Android Studio the stack looks fine.

Any ideas?

[lassade]

Full story: https://discord.com/channels/605571803288698900/1429809292747476992

TLDR:
with the latestes zig 0.16.0-dev.747+493ad58ff you will have to obj and link it your self adding --no-rosegment and -zseparate-code to the linker args.

[silbinarywolf]

Seems like others have hit this issue previously: android/ndk#1426 (comment)

Maybe a fix for upstream Zig could be something like adding a rule, similar to this one but instead it adds --no-rosegment
https://github.com/ziglang/zig/blob/4b5351bc0ddc248d6935d7d160a57cb4dfe4dedd/src/link/Lld.zig#L1003-L1010

Alternatively, it might be better to make the Zig Android SDK build logic work on the std.Build.Module to create an object file, then invoke the Android SDKs linker (ie. ~/Android/Sdk/build-tools/35.0.1/lld-bin/)

For example, maybe something in this logic here where we just get the artifact.root_module and get its object, then invoke lld directly to create the dynamic library:

var obj = b.addObject(.{
    .root_module = artifact.root_module,
    // NDK uses LLVM and LLD, for both of their use for consistency
    .use_llvm = true,
    .use_lld = true,
});

This logic would likely go here:

zig-android-sdk/src/androidbuild/apk.zig

Lines 431 to 437 in 870c7c2

	// Add build artifacts, usually a shared library targetting:
	// - aarch64-linux-android
	// - arm-linux-androideabi
	// - i686-linux-android
	// - x86_64-linux-android
	for (apk.artifacts.items, 0..) |artifact, artifact_index| {
	const target: ResolvedTarget = artifact.root_module.resolved_target orelse {

This isn't something I'm going to look at doing anytime soon as I'm not developing any Android applications for the time-being, but if someone wants to explore doing this work, I figured I'd at least write-up what I'm thinking.