Check allocations for OOM

src/backport.rs

@@ -22,7 +22,9 @@ pub(crate) mod alloc {
 
     pub mod alloc {
         use std::mem;
+        use std::process;
 
+        #[derive(Copy, Clone)]
         pub struct Layout {
             size: usize,
         }
@@ -47,5 +49,12 @@ pub(crate) mod alloc {
             let len_u16 = (layout.size + 1) / 2;
             unsafe { Vec::from_raw_parts(ptr as *mut u16, 0, len_u16) };
         }
+
+        pub fn handle_alloc_error(_layout: Layout) -> ! {
+            // This is unreachable because the alloc implementation above never
+            // returns null; Vec::reserve_exact would already have called std's
+            // internal handle_alloc_error.
+            process::abort();
+        }
     }
 }

src/identifier.rs

@@ -66,7 +66,7 @@
 // repr, leaving it available as a niche for downstream code. For example this
 // allows size_of::<Version>() == size_of::<Option<Version>>().
 
-use crate::alloc::alloc::{alloc, dealloc, Layout};
+use crate::alloc::alloc::{alloc, dealloc, handle_alloc_error, Layout};
 use core::mem;
 use core::num::{NonZeroU64, NonZeroUsize};
 use core::ptr::{self, NonNull};
@@ -123,6 +123,9 @@ impl Identifier {
                 let layout = unsafe { Layout::from_size_align_unchecked(size, align) };
                 // SAFETY: layout's size is nonzero.
                 let ptr = unsafe { alloc(layout) };
+                if ptr.is_null() {
+                    handle_alloc_error(layout);
+                }
                 let mut write = ptr;
                 let mut varint_remaining = len;
                 while varint_remaining > 0 {
@@ -203,6 +206,9 @@ impl Clone for Identifier {
             let layout = unsafe { Layout::from_size_align_unchecked(size, align) };
             // SAFETY: layout's size is nonzero.
             let clone = unsafe { alloc(layout) };
+            if clone.is_null() {
+                handle_alloc_error(layout);
+            }
             // SAFETY: new allocation cannot overlap the previous one (this was
             // not a realloc). The argument ptrs are readable/writeable
             // respectively for size bytes.