Revert 'Bump MSRV to 1.68'

.github/workflows/ci.yml

@@ -16,8 +16,9 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        # See top README for MSRV policy
-        rust_version: [1.68.0, stable]
+        # XXX: We are currently constrained by Winit's MSRV policy + CI system
+        # See Cargo.toml for details
+        rust_version: [1.64.0, stable]
     steps:
       - uses: actions/checkout@v3
 
@@ -34,7 +35,10 @@ jobs:
           i686-linux-android
 
       - name: Install cargo-ndk
-        run: cargo install cargo-ndk
+        # XXX: We have to use an old version of cargo-ndk that supports the
+        # libgcc linker workaround for rust < 1.68 because Winit's CI system
+        # currently requires this crate to be buildable with 1.64
+        run: cargo install cargo-ndk --version "^2"
 
       - name: Setup Java
         uses: actions/setup-java@v3

android-activity/Cargo.toml

@@ -9,7 +9,19 @@ repository = "https://github.com/rust-mobile/android-activity"
 documentation = "https://docs.rs/android-activity"
 description = "Glue for building Rust applications on Android with NativeActivity or GameActivity"
 license = "MIT OR Apache-2.0"
-rust-version = "1.68.0"
+
+# XXX: Even though we have our own MSRV policy that says we only promise to
+# support stable releases over the last three months we actually end up
+# constrained by the MSRV policy of Winit, which is currently based on
+# supporting Alacritty on Debian Sid, and requires a > 10 month old Rust version
+#
+# This Winit policiy is unfortunately in conflict with what makes sense for
+# Android because versions below 1.68 for Android requires awkward toolchain
+# linker workarounds, and can't even be compiled with newer versions of
+# `cargo ndk` that removed these linker workarounds.
+#
+# TODO: Open a PR for Winit's CI to test Android builds using a newer toolchain.
+rust-version = "1.64"
 
 [features]
 # Note: we don't enable any backend by default since features

android-activity/src/game_activity/mod.rs

@@ -759,6 +759,7 @@ extern "Rust" {
 // `app_main` function. This is run on a dedicated thread spawned
 // by android_native_app_glue.
 #[no_mangle]
+#[allow(unused_unsafe)] // Otherwise rust 1.64 moans about using unsafe{} in unsafe functions
 pub unsafe extern "C" fn _rust_glue_entry(native_app: *mut ffi::android_app) {
     abort_on_panic(|| {
         // Maybe make this stdout/stderr redirection an optional / opt-in feature?...

android-activity/src/native_activity/glue.rs

@@ -828,6 +828,7 @@ unsafe extern "C" fn on_content_rect_changed(
 
 /// This is the native entrypoint for our cdylib library that `ANativeActivity` will look for via `dlsym`
 #[no_mangle]
+#[allow(unused_unsafe)] // Otherwise rust 1.64 moans about using unsafe{} in unsafe functions
 extern "C" fn ANativeActivity_onCreate(
     activity: *mut ndk_sys::ANativeActivity,
     saved_state: *const libc::c_void,