Creating a dylib with Go

A small project showing how to create a dynamic library (dylib) using the basic Go compiler, and then how to incorporate and call that dylib from a Xojo desktop app.

(All macOS only.)

Download the Go compiler etc from golang.org...

The dylib is already prebuilt in the “go dylib” subdirectory, but to start from scratch, delete the dylib and simplemath.h files.

In the Terminal, cd to the directory, then run:

go build -buildmode=c-shared -o simplemath.dylib simplemath.go

The new dylib and header file are generated. (For our purposes here we don’t need the .h file.)

This dylib can then be used as you would any other.

Use in a Xojo app...

In a Xojo project, this is usually done by incorporating the dylib into your app via a copy build step (don’t forget that this copy step will come AFTER the main “compile and build” step).

The copy should (usually) be done to your app’s Frameworks directory.

In your code, you set up a constant with the path to your lib:

const dylibPath as String = "@executable_path/../Frameworks/simplemath.dylib"

(The @executable_path part of the path string above is not a Xojo feature as such, it’s part of OSX’s system of resolving dylib locations. A brief explanation of @executable path, @load path and @rpath.)

You can then test the availability of the functions using System.IsFunctionAvailable:

var isAvailable as Boolean = System.IsFunctionAvailable( "Add", dylibPath )

To actually use the function:

soft declare function Add lib dylibPath ( x as integer, y as integer ) as integer

var result as Integer = Add( 1, 2 )

If you are not using IsFunctionAvailable, or you want to be ultra-safe you might wrap the whole thing with some exception handling:

try
  
    soft declare function Add lib dylibPath ( x as integer, y as integer ) as integer
  
    var result as Integer = Add( 1, 2 )

catch e as FunctionNotFoundException
  
    // various ways of checking e, via e.Message, e.ErrorNumber etc, to see what the problem is
  
end try

Xojo Documention for “FunctionNotFoundException”