add to CI

.github/workflows/fuzz.yml

@@ -22,4 +22,5 @@ jobs:
         set -e
         (cd profiling && cargo bolero test collections::string_table::tests::fuzz_string_table -T 1min)
         (cd profiling && cargo bolero test collections::string_table::tests::fuzz_arena_allocator -T 1min)
+        (cd alloc && cargo bolero test chain::tests::fuzz -T 1min)
 

alloc/src/chain.rs

@@ -238,10 +238,7 @@ unsafe impl<A: Allocator + Clone> Allocator for ChainAllocator<A> {
 
         debug_assert!(chain_node.remaining_capacity() >= layout.size());
 
-        let result = chain_node.linear.allocate(layout);
-        // If this fails, there's a bug in the allocator.
-        debug_assert!(result.is_ok());
-        result
+        chain_node.linear.allocate(layout)
     }
 
     unsafe fn deallocate(&self, _ptr: NonNull<u8>, _layout: Layout) {
@@ -290,29 +287,59 @@ mod tests {
     use super::*;
     use allocator_api2::alloc::Global;
 
+    /// https://doc.rust-lang.org/beta/std/primitive.pointer.html#method.is_aligned_to
+    /// Convenience function until the std lib standardizes this.
+    fn is_aligned_to<T: ?Sized>(p: *const T, align: usize) -> bool {
+        (p as *const u8 as usize) % align == 0
+    }
+
     #[test]
     fn fuzz() {
         bolero::check!()
-            .with_type::<(usize, usize, u32)>()
-            .for_each(|(size_hint, size, align_bits)| {
+            .with_type::<(usize, Vec<(usize, u32, usize, u8)>)>()
+            .for_each(|(size_hint, size_align_vec)| {
+                const MAX_SIZE: usize = 0x10000000;
+                // avoid SUMMARY: libFuzzer: out-of-memory
+                if *size_hint > MAX_SIZE {
+                    return;
+                }
                 let allocator = ChainAllocator::new_in(*size_hint, Global);
-                if *size == 0 {return};
-                assert!(false);
 
-                // for now, only test 2**8 alignments
-                if *align_bits > 8 {return};
-                let Some(align) = 2usize.checked_pow(*align_bits) else {
-                    return;
-                };
-                assert!(false);
+                for (size, align_bits, idx, val) in size_align_vec {
+                    if *size == 0 || *size > MAX_SIZE {
+                        return;
+                    };
+                    if idx >= size {
+                        return;
+                    }
 
-                let Ok(layout) = Layout::from_size_align(*size, align) else {
-                    return;
-                };
-                let ptr = allocator.allocate(layout).unwrap();
-                // deallocate doesn't return memory to the allocator, but it shouldn't
-                // panic, as that prevents its use in containers like Vec.
-                unsafe { allocator.deallocate(ptr.cast(), layout) };
+                    // Exit early if the alignment alone would be too big
+                    if *align_bits > 32 {
+                        return;
+                    };
+
+                    let align = 1usize << *align_bits;
+                    let layout = Layout::from_size_align(*size, align).unwrap();
+
+                    if layout.pad_to_align().size() > MAX_SIZE {
+                        return;
+                    };
+
+                    if let Ok(mut ptr) = allocator.allocate(layout) {
+                        assert!(is_aligned_to(ptr.as_ptr(), align));
+                        let obj = unsafe { ptr.as_mut() };
+                        // The object is guaranteed to be at least size, but can be larger
+                        assert!(obj.len() >= *size);
+
+                        // Test that writing and reading a random index in the object works.
+                        obj[*idx] = *val;
+                        assert_eq!(obj[*idx], *val);
+
+                        // deallocate doesn't return memory to the allocator, but it shouldn't
+                        // panic, as that prevents its use in containers like Vec.
+                        unsafe { allocator.deallocate(ptr.cast(), layout) };
+                    }
+                }
             })
     }