add.zig

const std = @import("std");

pub fn add(a: u32, b: u32) !u32 {
    return a + b + try getExtraVal();
}

const envVarName = "EXTRA_VAL";

fn getExtraVal() !u32 {
    // Just a little hack, linking libc wasn't working.
    const old = std.os.environ;
    defer std.os.environ = old;
    std.os.environ = makeSlice();

    if (!std.process.hasEnvVarConstant(envVarName)) {
        return error.MissingEnvVar;
    }

    return std.process.parseEnvVarInt(envVarName, u32, 10);
}

extern var environ: [*][*:0]u8;

fn makeSlice() [][*:0]u8 {
    var count: usize = 0;
    while (@as(?[*:0]u8, environ[count])) |_| : (count += 1) {}
    return environ[0..count];
}