Arrays: Zero new items of trivial types on resize() (bindings only)

This is not enabled by default in the core version for performance reasons,
as Vector/CowData are used in critical code paths where not zero'ing memory
which is going to be set later on can be important.

But for bindings / the scripting API, we make zero the new items by default
(which already happened for built types like Vector3, etc., but not for
trivial types like int, float).

Fixes #43033.

Co-authored-by: David Hoppenbrouwers <david@salt-inc.org>

2 files changed, 5 insertions, 0 deletions

diff --git a/core/templates/cowdata.h b/core/templates/cowdata.h
index e760fc2176..5f13f4a6be 100644
--- a/core/templates/cowdata.h
+++ b/core/templates/cowdata.h
@@ -158,6 +158,7 @@ public:
 		return _ptr[p_index];
 	}
 
+	template <bool p_ensure_zero = false>
 	Error resize(int p_size);
 
 	_FORCE_INLINE_ void remove_at(int p_index) {
@@ -257,6 +258,7 @@ uint32_t CowData<T>::_copy_on_write() {
 }
 
 template <class T>
+template <bool p_ensure_zero>
 Error CowData<T>::resize(int p_size) {
 	ERR_FAIL_COND_V(p_size < 0, ERR_INVALID_PARAMETER);
 
@@ -306,6 +308,8 @@ Error CowData<T>::resize(int p_size) {
 			for (int i = *_get_size(); i < p_size; i++) {
 				memnew_placement(&_ptr[i], T);
 			}
+		} else if (p_ensure_zero) {
+			memset((void *)(_ptr + current_size), 0, (p_size - current_size) * sizeof(T));
 		}
 
 		*_get_size() = p_size;
diff --git a/core/templates/vector.h b/core/templates/vector.h
index f3f5ed76a7..51595a75f5 100644
--- a/core/templates/vector.h
+++ b/core/templates/vector.h
@@ -89,6 +89,7 @@ public:
 	_FORCE_INLINE_ void set(int p_index, const T &p_elem) { _cowdata.set(p_index, p_elem); }
 	_FORCE_INLINE_ int size() const { return _cowdata.size(); }
 	Error resize(int p_size) { return _cowdata.resize(p_size); }
+	Error resize_zeroed(int p_size) { return _cowdata.template resize<true>(p_size); }
 	_FORCE_INLINE_ const T &operator[](int p_index) const { return _cowdata.get(p_index); }
 	Error insert(int p_pos, T p_val) { return _cowdata.insert(p_pos, p_val); }
 	int find(const T &p_val, int p_from = 0) const { return _cowdata.find(p_val, p_from); }