gvalue

GValue is a generic value container in the GLib/GObject type system. It is designed to hold a value of any type registered in the GType system, enabling generic property access, signal marshalling, and value passing in a type-safe way. GValue is commonly used by the GObject property system and related APIs, and it provides a uniform mechanism to store, copy, and transfer values of diverse types.

A GValue must be initialized with a specific GType using g_value_init, which establishes the type of value that the container will hold. Once initialized, values can be set and retrieved with type-specific functions such as g_value_set_int, g_value_get_int, g_value_set_string, and g_value_get_string. There are corresponding “take” and “copy” operations to manage ownership and lifetime of stored data, for example g_value_copy duplicates a value and g_value_unset frees resources held by the container. The type safety of operations is enforced at runtime; attempting to set a value with an incompatible type can trigger warnings or errors.

GValue supports a variety of GTypes, including primitive types, strings, pointers, objects, and boxed types. Some stored values require special memory handling, so developers should use the appropriate take or free functions as documented for each type. The lifecycle of a GValue typically involves initialization, optional set/get operations, copying when needed, and unsetting to release resources.

In practice, GValue is most relevant for interacting with GObject properties, signal marshalling, and wrappers that need to abstract over multiple possible types. For newer code emphasizing modern data interchange, GLib also provides other mechanisms such as GVariant, but GValue remains a core, compatible facility within the GLib ecosystem.