Zigの色々なAllocator

const std = @import("std");
const builtin = @import("builtin");

// Global variable
// pub var allocator: std.mem.Allocator = undefined;

pub fn main() !void {
    {
        // General Purpose
        var general_purpose_allocator = std.heap.GeneralPurposeAllocator(.{}){};
        const gpa = general_purpose_allocator.allocator();

        _ = gpa;
    }
    {
        // Heap
        var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
        defer arena.deinit();
        const allocator = arena.allocator();

        _ = allocator;
    }
    {
        // C allocator :: -lc or exe.linkLibC()
        var arr = std.ArrayList(u8).init(std.heap.c_allocator);
        try arr.append('z');
    }
    {
        // Fixed Buffer (stack)
        var buffer: [10]u8 = undefined;
        var fba = std.heap.FixedBufferAllocator.init(&buffer);
        const allocator = fba.allocator();

        const a = try allocator.alloc(u8, 10);
        _ = a;
        // const b = try allocator.alloc(u8, 1); // OOM
        // _ = b;
    }
    {
        // GPA(debug) and c_allocator(release)
        var gpa = std.heap.GeneralPurposeAllocator(.{}){};
        const allocator = if (builtin.mode == .Debug) gpa.allocator() else std.heap.c_allocator;
        defer if (builtin.mode == .Debug) std.debug.assert(gpa.deinit() == .ok);
        _ = allocator;
    }
}