extmodules

Extmodules, or external modules, are software components that extend the functionality of a host application without changing its core codebase. They are packaged separately and loaded into the host at runtime, enabling customization and feature expansion while maintaining a stable base system.

An extmodule typically exposes a defined interface or set of entry points that the host calls to register functionality, handle events, or extend data models. A module manifest or descriptor often specifies the module's name, version, author, dependencies, and compatible host versions. A module loader or plugin manager in the host handles discovery, validation, loading, initialization, and, if supported, unloading.

Loading can occur through dynamic linking of shared libraries (for example, platform-specific .dll, .so, or .dylib files) or via interpreters and scripting languages that load modules at runtime. Some ecosystems use a registry or plugin directory to locate extmodules.

Development and deployment considerations include maintaining stable APIs, abi compatibility, clear documentation of dependencies, version pinning, and minimal startup overhead. Security concerns involve signing, trust models, isolation, and sandboxing to prevent a loaded module from compromising the host or other data. Testing should cover compatibility across host versions and platforms.

Common domains for extmodules include kernel or system plugins, database extensions that add functions or data types, language runtimes that support native extensions, and application ecosystems that rely on plugins or addons to provide extra tools and integrations.

See also: plugin architecture, extension mechanism, dynamic loading, module system.