Ada-Zig-FFI

Ada bindings for calling Zig libraries via FFI.

Overview

This library provides type-safe Ada bindings to Zig libraries. Zig exports C-compatible functions that Ada can call through its Interfaces.C mechanism.

Architecture

Ada → Interfaces.C → Zig (C ABI)

Ada’s pragma Import(C, …​) can directly call C-compatible functions exported by Zig shared libraries.

Usage

Importing Zig Functions

with Interfaces.C;
use Interfaces.C;

package Zig_Lib is
   -- Import Zig function
   function Add (A, B : int) return int
      with Import => True,
           Convention => C,
           External_Name => "add";

   function Multiply (A, B : int) return int
      with Import => True,
           Convention => C,
           External_Name => "multiply";
end Zig_Lib;

Using the Bindings

with Ada.Text_IO;
with Zig_Lib;

procedure Main is
   Result : Interfaces.C.int;
begin
   Result := Zig_Lib.Add (2, 3);
   Ada.Text_IO.Put_Line ("2 + 3 =" & Result'Image);
end Main;

Building

Building Zig Library

cd zig-lib
zig build -Doptimize=ReleaseFast

Building Ada Project

gprbuild -P ada_zig_ffi.gpr

Linking

-- In your .gpr file:
package Linker is
   for Default_Switches ("Ada") use ("-L./zig-lib/zig-out/lib", "-lzigffi");
end Linker;

Type Mappings

Ada Type	Zig Type	Notes
Interfaces.C.int	c_int / i32	C int
Interfaces.C.long	c_long / i64	C long
Interfaces.C.unsigned	c_uint / u32	C unsigned
Interfaces.C.double	f64	64-bit float
Interfaces.C.char_array	[*:0]const u8	String
System.Address	*anyopaque	Raw pointer

Safety Considerations

Ada’s strong typing provides additional safety when calling Zig code:

• Type mismatches are caught at compile time

• Range checks can validate Zig return values

• Pre/postconditions can wrap FFI calls

Examples

The examples/ directory contains complete working examples:

Basic Example

Demonstrates calling Zig functions from Ada:

cd examples
gprbuild -P examples.gpr basic_example.adb
./bin/basic_example

Features demonstrated: * Version information retrieval * Arithmetic operations (add, multiply) * Mathematical functions (factorial, fibonacci) * String operations

Callback Example

Demonstrates bidirectional FFI with callbacks from Zig to Ada:

cd examples
gprbuild -P examples.gpr callback_example.adb
./bin/callback_example

Features demonstrated: * Registering Ada procedures as callbacks * Invoking callbacks from Zig * Iterator pattern with Ada-style termination control

Safety Example

Demonstrates safety-critical patterns with error handling:

cd examples
gprbuild -P examples.gpr safety_example.adb
./bin/safety_example

Features demonstrated: * Safe division with error callbacks * Bounds-checked array access * Buffer operations

RSR Compliance

This library follows the Rhodium Standard Repository guidelines:

• Ada for safety-critical systems

• Zig for performance-critical FFI

• No C wrapper code required

License

PMPL-1.0-or-later