[][src]Crate dlopen

Library for opening and working with dynamic link libraries (also known as shared object).


This library is an effort to make use of dynamic link libraries in Rust simple. Previously existing solutions were either unsafe, provided huge overhead of required writing too much code to achieve simple things. I hope that this library will help you to quickly get what you need and avoid errors.

Quick example

extern crate dlopen;
extern crate dlopen_derive;
use dlopen::wrapper::{Container, WrapperApi};

struct Api<'a> {
    example_rust_fun: fn(arg: i32) -> u32,
    example_c_fun: unsafe extern "C" fn(),
    example_reference: &'a mut i32,

fn main(){
    let mut cont: Container<Api> =
        unsafe { Container::load("libexample.so") }.expect("Could not open library or load symbols");
    *cont.example_reference_mut() = 5;


Main features

  • Supports majority of platforms and is platform independent.
  • Is consistent with Rust error handling mechanism and makes making mistakes much more difficult.
  • Is very lightweight. It mostly uses zero cost wrappers to create safer abstractions over platform API.
  • Is thread safe.
  • Is object-oriented programming friendly.
  • Has a low-level API that provides full flexibility of using libraries.
  • Has two high-level APIs that protect against dangling symbols - each in its own way.
  • High level APIs support automatic loading of symbols into structures. You only need to define a structure that represents an API. The rest happens automatically and requires only minimal amount of code.
  • Automatic loading of symbols helps you to follow the DRY paradigm.

Compare with other libraries

Basic functionalityYesYesYes
Dangling symbol preventionYesYesYes
Thread safetyYesPotential problem with SetErrorMode() on older Windows platformsNo support for SetErrorMode (library may block the application on Windows)
Loading of symbols into structuresYesNoNo
OverheadMinimalMinimalSome overhead
Low-level, unsafe APIYesYesYes
Object-oriented friendlyYesNoYes
Load from the program itselfYesNoNo
Obtaining address information (dladdr)YesUnix onlyNo


Please note that while Rust aims at being 100% safe language, it does not yet provide mechanisms that would allow me to create a 100% safe library, so I had to settle on 99%. Also the nature of dynamic link libraries requires casting obtained pointers into types that are defined on the application side. And this cannot be safe. Having said that I still think that this library provides the best approach and greatest safety possible in Rust.



dlopen = "0.1"


Cargo documentation




This code is licensed under MIT license.


Special thanks to Simonas Kazlauskas whose libloading became code base for my project.

Comparison of APIs:

  • raw - a low-level API. It is mainly intended to give you full flexibility if you decide to create you own custom solution for handling dynamic link libraries. For typical operations you probably should use one of high-level APIs.

  • symbor - a high-level API. It prevents dangling symbols by creating zero cost structural wrappers around symbols obtained from the library. These wrappers use Rust borrowing mechanism to make sure that the library will never get released before obtained symbols.

  • wrapper - a high-level API. It prevents dangling symbols by creating zero cost functional wrappers around symbols obtained from the library. These wrappers prevent accidental copying of raw symbols from library API. Dangling symbols are prevented by keeping library and its API in one structure - this makes sure that symbols and library are released together.

Additionally both high-level APIs provide a way to automatically load symbols into a structure using Rust reflection mechanism. Decision which API should be used is a matter of taste - please check documentation of both of them and use the one that you prefer. At the moment none seems to have any reasonable advantage over the other.



Low-level API for opening and getting raw symbols from dynamic link libraries.


High-level and safe API for opening and getting symbols from dynamic libraries. It is based on symbol borrowing mechanism and supports automatic loading of symbols into structures.


Utilities for working with dynamic link libraries.


High-level and safe API for opening and getting symbols from dynamic link libraries. It is based on wrapping private symbols with public functions to prevent direct access and supports automatic loading of symbols into structures.



This is a library-specific error that is returned by all calls to all APIs.