// Copyright 2016 The Go Authors. All rights reserved. // Use of this source code is governed by a BSD-style // license that can be found in the LICENSE file. // Package plugin implements loading and symbol resolution of Go plugins. // // A plugin is a Go main package with exported functions and variables that // has been built with: // // go build -buildmode=plugin // // When a plugin is first opened, the init functions of all packages not // already part of the program are called. The main function is not run. // A plugin is only initialized once, and cannot be closed. // // # Warnings // // The ability to dynamically load parts of an application during // execution, perhaps based on user-defined configuration, may be a // useful building block in some designs. In particular, because // applications and dynamically loaded functions can share data // structures directly, plugins may enable very high-performance // integration of separate parts. // // However, the plugin mechanism has many significant drawbacks that // should be considered carefully during the design. For example: // // - Plugins are currently supported only on Linux, FreeBSD, and // macOS, making them unsuitable for applications intended to be // portable. // // - Applications that use plugins may require careful configuration // to ensure that the various parts of the program be made available // in the correct location in the file system (or container image). // By contrast, deploying an application consisting of a single static // executable is straightforward. // // - Reasoning about program initialization is more difficult when // some packages may not be initialized until long after the // application has started running. // // - Bugs in applications that load plugins could be exploited by // an attacker to load dangerous or untrusted libraries. // // - Runtime crashes are likely to occur unless all parts of the // program (the application and all its plugins) are compiled // using exactly the same version of the toolchain, the same build // tags, and the same values of certain flags and environment // variables. // // - Similar crashing problems are likely to arise unless all common // dependencies of the application and its plugins are built from // exactly the same source code. // // - Together, these restrictions mean that, in practice, the // application and its plugins must all be built together by a // single person or component of a system. In that case, it may // be simpler for that person or component to generate Go source // files that blank-import the desired set of plugins and then // compile a static executable in the usual way. // // For these reasons, many users decide that traditional interprocess // communication (IPC) mechanisms such as sockets, pipes, remote // procedure call (RPC), shared memory mappings, or file system // operations may be more suitable despite the performance overheads. package plugin // Plugin is a loaded Go plugin. type Plugin struct { pluginpath string err string // set if plugin failed to load loaded chan struct{} // closed when loaded syms map[string]any } // Open opens a Go plugin. // If a path has already been opened, then the existing *[Plugin] is returned. // It is safe for concurrent use by multiple goroutines. func Open(path string) (*Plugin, error) { return open(path) } // Lookup searches for a symbol named symName in plugin p. // A symbol is any exported variable or function. // It reports an error if the symbol is not found. // It is safe for concurrent use by multiple goroutines. func (p *Plugin) Lookup(symName string) (Symbol, error) { return lookup(p, symName) } // A Symbol is a pointer to a variable or function. // // For example, a plugin defined as // // package main // // import "fmt" // // var V int // // func F() { fmt.Printf("Hello, number %d\n", V) } // // may be loaded with the [Open] function and then the exported package // symbols V and F can be accessed // // p, err := plugin.Open("plugin_name.so") // if err != nil { // panic(err) // } // v, err := p.Lookup("V") // if err != nil { // panic(err) // } // f, err := p.Lookup("F") // if err != nil { // panic(err) // } // *v.(*int) = 7 // f.(func())() // prints "Hello, number 7" type Symbol any