1 files changed, 67 insertions, 0 deletions
diff --git a/tests/run-make/wasm-exceptions-nostd/src/arena_alloc.rs b/tests/run-make/wasm-exceptions-nostd/src/arena_alloc.rs
new file mode 100644
index 000000000..572d25330
--- /dev/null
+++ b/tests/run-make/wasm-exceptions-nostd/src/arena_alloc.rs
@@ -0,0 +1,67 @@
+use core::alloc::{GlobalAlloc, Layout};
+use core::cell::UnsafeCell;
+
+#[global_allocator]
+static ALLOCATOR: ArenaAllocator = ArenaAllocator::new();
+
+/// Very simple allocator which never deallocates memory
+///
+/// Based on the example from
+/// https://doc.rust-lang.org/stable/std/alloc/trait.GlobalAlloc.html
+pub struct ArenaAllocator {
+    arena: UnsafeCell<Arena>,
+}
+
+impl ArenaAllocator {
+    pub const fn new() -> Self {
+        Self {
+            arena: UnsafeCell::new(Arena::new()),
+        }
+    }
+}
+
+/// Safe because we are singlethreaded
+unsafe impl Sync for ArenaAllocator {}
+
+unsafe impl GlobalAlloc for ArenaAllocator {
+    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+        let arena = &mut *self.arena.get();
+        arena.alloc(layout)
+    }
+
+    unsafe fn dealloc(&self, _ptr: *mut u8, _layout: Layout) {}
+}
+
+const ARENA_SIZE: usize = 64 * 1024; // more than enough
+
+#[repr(C, align(4096))]
+struct Arena {
+    buf: [u8; ARENA_SIZE], // aligned at 4096
+    allocated: usize,
+}
+
+impl Arena {
+    pub const fn new() -> Self {
+        Self {
+            buf: [0x55; ARENA_SIZE],
+            allocated: 0,
+        }
+    }
+
+    pub unsafe fn alloc(&mut self, layout: Layout) -> *mut u8 {
+        if layout.align() > 4096 || layout.size() > ARENA_SIZE {
+            return core::ptr::null_mut();
+        }
+
+        let align_minus_one = layout.align() - 1;
+        let start = (self.allocated + align_minus_one) & !align_minus_one; // round up
+        let new_cursor = start + layout.size();
+
+        if new_cursor >= ARENA_SIZE {
+            return core::ptr::null_mut();
+        }
+
+        self.allocated = new_cursor;
+        self.buf.as_mut_ptr().add(start)
+    }
+}