Principle:Tensorflow Serving Type Safe Erasure
| Knowledge Sources | |
|---|---|
| Domains | Type System |
| Last Updated | 2026-02-13 00:00 GMT |
Overview
A type erasure technique that wraps void pointers with compile-time type identifiers, providing type-safe access that returns nullptr on type mismatch rather than allowing unsafe casts.
Description
Type-Safe Erasure addresses the need for heterogeneous containers or polymorphic return types where the actual type varies but intermediate code is type-agnostic. The approach stores a void pointer alongside a type identifier generated at compile time using the address of a static local variable (one per type instantiation). This FastTypeId technique avoids RTTI overhead and works across shared library boundaries within a single binary. When accessing the stored value, the requested type's identifier is compared against the stored identifier; a mismatch returns nullptr rather than performing an unsafe cast. This pattern extends to owning semantics (UniqueAnyPtr) by pairing the type-erased pointer with a type-erased deleter (a function pointer that knows the correct type for deletion). The deleter is also generated via template instantiation, maintaining zero overhead compared to a virtual destructor approach.
Usage
Use this when you need to pass or store objects of varying types through type-agnostic interfaces, such as managing heterogeneous dependencies or implementing containers that hold objects of different types. It should be used when two disjoint pieces of code agree on a type but the intermediary is agnostic.
Theoretical Basis
This technique is a form of type erasure, a fundamental concept in generic programming where type information is hidden behind a uniform interface. The FastTypeId approach is a compile-time type tagging mechanism that exploits the C++ guarantee that each function-local static variable has a unique address. It is related to std::any (C++17) but more lightweight, and to boost::any but without RTTI. The owning variant follows the type-erased deleter pattern used in std::shared_ptr, but with function pointers instead of std::function for zero overhead.