ObjectSpace

ObjectSpace is a term used in several programming environments to describe the set of all live objects currently allocated in a program's memory, or a runtime facility to inspect and manipulate that set. It serves as an abstraction for introspection, debugging, and memory profiling by exposing the objects that exist during execution and, in some systems, their relationships.

In Ruby, ObjectSpace is a module that provides facilities to enumerate living objects and interact with the garbage collector. It includes methods that allow iterating over objects of a given class and gathering information about memory usage. This can help detect leaks, analyze object lifetimes, or study memory patterns, but it can incur performance overhead and may not enumerate every object in all runtimes.

In Smalltalk environments, notably Squeak and Pharo, the runtime concept often described as object space or object memory refers to the heap that stores all Smalltalk objects. Tools integrated with the image expose the object graph, enabling inspection of individual objects, references, and memory usage. This supports live programming and incremental development by providing a view of objects as the program runs.

Beyond these specific implementations, object space is used in a broader sense to describe the abstraction for object identity and lifetime within a runtime, with implications for memory management and debugging. Limitations typically include partial visibility of non-managed resources, performance costs, and variations across runtimes.

See also: garbage collection, memory profiling, reflection, debugging, object graph.