sizeof(Node0) also needs to be < kBytesPerKey

Also remove vestigial comment.

CC #9

ConflictSet.cpp

@@ -47,9 +47,7 @@ limitations under the License.
 #if __has_builtin(__builtin_assume)
 #define assume(e) __builtin_assume(e)
 #else
-#define assume(e)                                                              \
-  if (!(e))                                                                    \
-  __builtin_unreachable()
+#define assume(e) __attribute__((assume(e)))
 #endif
 #else
 #define assume assert
@@ -145,20 +143,20 @@ private:
 };
 
 bool BitSet::test(int i) const {
-  assume(0 <= i);
-  assume(i < 256);
+  assert(0 <= i);
+  assert(i < 256);
   return words[i >> 6] & (uint64_t(1) << (i & 63));
 }
 
 void BitSet::set(int i) {
-  assume(0 <= i);
-  assume(i < 256);
+  assert(0 <= i);
+  assert(i < 256);
   words[i >> 6] |= uint64_t(1) << (i & 63);
 }
 
 void BitSet::reset(int i) {
-  assume(0 <= i);
-  assume(i < 256);
+  assert(0 <= i);
+  assert(i < 256);
   words[i >> 6] &= ~(uint64_t(1) << (i & 63));
 }
 
@@ -273,9 +271,8 @@ static_assert(sizeof(Node256) < kMinChildrenNode256 * kBytesPerKey);
 static_assert(sizeof(Node48) < kMinChildrenNode48 * kBytesPerKey);
 static_assert(sizeof(Node16) < kMinChildrenNode16 * kBytesPerKey);
 static_assert(sizeof(Node4) < kMinChildrenNode4 * kBytesPerKey);
+static_assert(sizeof(Node0) < kBytesPerKey);
 
-// Bounds memory usage in free list, but does not account for memory for partial
-// keys.
 template <class T, int64_t kMemoryBound = (1 << 20),
           int64_t kMaxIndividual = (1 << 10)>
 struct BoundedFreeListAllocator {
@@ -958,7 +955,7 @@ struct SearchStepWise {
   SearchStepWise() {}
   SearchStepWise(Node *n, std::span<const uint8_t> remaining)
       : n(n), remaining(remaining) {
-    assume(n->partialKeyLen == 0);
+    assert(n->partialKeyLen == 0);
   }
 
   bool step() {
@@ -1582,7 +1579,7 @@ template <bool kBegin>
         auto *old = *self;
         int64_t oldMaxVersion = maxVersion(old, impl);
 
-        *self = allocators->node4.allocate(partialKeyIndex);
+        *self = allocators->node0.allocate(partialKeyIndex);
 
         memcpy((char *)*self + kNodeCopyBegin, (char *)old + kNodeCopyBegin,
                kNodeCopySize);