Index: godot-cpp/include/core/Defs.hpp
--- godot-cpp/include/core/Defs.hpp.orig
+++ godot-cpp/include/core/Defs.hpp
@@ -92,6 +92,8 @@ enum class Error {
 // alloca() is non-standard. When using MSVC, it's in malloc.h.
 #if defined(__linux__) || defined(__APPLE__)
 #include <alloca.h>
+#elif defined(__OpenBSD__)
+#include <stdlib.h>
 #else
 #include <malloc.h>
 #endif
