test: add test case cannot_alloc_max_usize_minus_some

crates/rlsf/tests/global.rs

@@ -1,6 +1,9 @@
 // Adopted from
 // https://github.com/alexcrichton/dlmalloc-rs/blob/master/tests/global.rs
-use std::collections::HashMap;
+use std::{
+    alloc::{GlobalAlloc, Layout},
+    collections::HashMap,
+};
 
 #[global_allocator]
 #[cfg(any(all(target_arch = "wasm32", not(target_feature = "atomics")), unix))]
@@ -52,3 +55,15 @@ fn test_larger_than_word_alignment() {
         }
     }
 }
+
+#[test]
+fn cannot_alloc_max_usize_minus_some() {
+    // The test should complete without causing OOM
+    for offset in (0..64).step_by(8) {
+        let layout = Layout::from_size_align(usize::MAX - offset, 1).unwrap();
+        for _ in 0..1000000 {
+            let result = unsafe { A.alloc(layout) };
+            assert!(result.is_null());
+        }
+    }
+}