Dynamic libraries

std::dynlib opens a loadable library and binds an extern interface. It is how a compiled Echo app loads a #[target: lib] it did not have at link time.

use std::dynlib;

echo dynlib::file_name('greeter');

On Darwin that prints libgreeter.dylib. On Linux libgreeter.so. On Windows greeter.dll. WASI does not compile this namespace: there is no dlopen there.

The contract is Extern interfaces. The host recipe is Libraries and plugins. This page is the surface.

library::open

use std::dynlib;

dynlib::library $plug = guard dynlib::library::open($path) else ($e) {
    echo $e->message();
    return 1;
};

The path is the path. No lib prefix, no suffix invented. A missing file is dynerror::not_found. A dlopen failure is load_failed.

The class owns the handle. Dropping the last binding unloads the image. There is no close().

bind and load

greeter $g = guard dynlib::load<greeter>($dir, 'english') else ($e) {
    die($e->message());
};
echo $g->add(2, 3);

load is open(path_of($dir, $name)) then bind<T>(). Missing table is missing_interface. A header that does not match is abi_mismatch. bind_symbols<T>() fills slots by each requirement's link name instead.

address

string $name = 'add';
ptr<uint8> $raw = guard $plug->address($name) else {
    die('missing export');
};

unsafe {
    extern function<int32(int32, int32)> $add =
        $raw:$ as extern function<int32(int32, int32)>;
    echo $add(2, 3);
}

A missing name is null. The recast is your promise, and it is unsafe. Bind the name to a local first: passing 'add' straight into address will not compile.

file_name and path_of

use std::dynlib;

echo dynlib::file_name('greeter');

path_of($dir, $stem) joins them with a slash. load uses that.

Next

• Extern interfaces
• Libraries and plugins
• C interop for extern function<...>