Add basic allocator

library/std/src/sys/pal/mikros/alloc.rs

@@ -1,23 +1,26 @@
-use crate::alloc::{GlobalAlloc, Layout, System};
-use crate::ptr::null_mut;
+use crate::{
+    alloc::{GlobalAlloc, Layout, System},
+    ptr::null_mut,
+};
+
+static mut HEAP: [u8; 16384] = [0u8; 16384];
+static mut HEAP_USED: usize = 0;
 
 #[stable(feature = "alloc_system_type", since = "1.28.0")]
 unsafe impl GlobalAlloc for System {
     #[inline]
-    unsafe fn alloc(&self, _layout: Layout) -> *mut u8 {
-        null_mut()
-    }
-
-    #[inline]
-    unsafe fn alloc_zeroed(&self, _layout: Layout) -> *mut u8 {
-        null_mut()
+    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+        unsafe {
+            if 16384 - HEAP_USED < layout.size() {
+                null_mut()
+            } else {
+                let ptr = &mut HEAP[HEAP_USED] as *mut u8;
+                HEAP_USED += layout.size();
+                ptr
+            }
+        }
     }
 
     #[inline]
     unsafe fn dealloc(&self, _ptr: *mut u8, _layout: Layout) {}
-
-    #[inline]
-    unsafe fn realloc(&self, _ptr: *mut u8, _layout: Layout, _new_size: usize) -> *mut u8 {
-        null_mut()
-    }
 }