libexpr: Move *StackReservation constants to gc-small-vector.hh

There are other places where it's useful to use these constants
(notably in eval.hh).

src/libexpr/include/nix/expr/gc-small-vector.hh

@@ -26,4 +26,20 @@ using SmallValueVector = SmallVector<Value *, nItems>;
 template<size_t nItems>
 using SmallTemporaryValueVector = SmallVector<Value, nItems>;
 
+/**
+ * For functions where we do not expect deep recursion, we can use a sizable
+ * part of the stack a free allocation space.
+ *
+ * Note: this is expected to be multiplied by sizeof(Value), or about 24 bytes.
+ */
+constexpr size_t nonRecursiveStackReservation = 128;
+
+/**
+ * Functions that maybe applied to self-similar inputs, such as concatMap on a
+ * tree, should reserve a smaller part of the stack for allocation.
+ *
+ * Note: this is expected to be multiplied by sizeof(Value), or about 24 bytes.
+ */
+constexpr size_t conservativeStackReservation = 16;
+
 } // namespace nix

src/libexpr/include/nix/expr/primops.hh

@@ -8,22 +8,6 @@
 
 namespace nix {
 
-/**
- * For functions where we do not expect deep recursion, we can use a sizable
- * part of the stack a free allocation space.
- *
- * Note: this is expected to be multiplied by sizeof(Value), or about 24 bytes.
- */
-constexpr size_t nonRecursiveStackReservation = 128;
-
-/**
- * Functions that maybe applied to self-similar inputs, such as concatMap on a
- * tree, should reserve a smaller part of the stack for allocation.
- *
- * Note: this is expected to be multiplied by sizeof(Value), or about 24 bytes.
- */
-constexpr size_t conservativeStackReservation = 16;
-
 struct RegisterPrimOp
 {
     typedef std::vector<PrimOp> PrimOps;