diff --git a/lib/CGroup.zig b/lib/CGroup.zig
new file mode 100644
index 0000000..2ba9c4d
--- /dev/null
+++ b/lib/CGroup.zig
@@ -0,0 +1,6 @@
+const CGroup = @This();
+
+gid: u32,
+name: [:0]const u8,
+// https://github.com/ziglang/zig/issues/7517
+members: [:null]const ?[*:0]const u8,
diff --git a/lib/Corpus.zig b/lib/Corpus.zig
index 9914f44..80219c5 100644
--- a/lib/Corpus.zig
+++ b/lib/Corpus.zig
@@ -86,7 +86,7 @@ pub fn init(
         members.len = 0;
 
         for (groupmembers) |member_name| {
-            if (name2user.get(member_name.?)) |user_idx| {
+            if (name2user.get(member_name)) |user_idx| {
                 members.len += 1;
                 members[members.len - 1] = user_idx;
                 try user2groups[user_idx].append(allocator, @intCast(u32, i));
@@ -203,16 +203,16 @@ pub fn testCorpus(allocator: Allocator) !Corpus {
         .shell = "/usr/sbin/nologin",
     } };
 
-    var members0 = &[_:null]?[*:0]const u8{"root"};
-    var members1 = &[_:null]?[*:0]const u8{"vidmantas"};
-    var members2 = &[_:null]?[*:0]const u8{ "svc-bar", "vidmantas" };
-    var members3 = &[_:null]?[*:0]const u8{ "svc-bar", "Name" ** 8, "vidmantas", "root" };
+    var members0 = &[_][]const u8{"root"};
+    var members1 = &[_][]const u8{"vidmantas"};
+    var members2 = &[_][]const u8{ "svc-bar", "vidmantas" };
+    var members3 = &[_][]const u8{ "svc-bar", "Name" ** 8, "vidmantas", "root" };
 
     const groups = [_]Group{
-        Group{ .gid = 0, .name = "root", .members = members0 },
-        Group{ .gid = 128, .name = "vidmantas", .members = members1 },
-        Group{ .gid = 9999, .name = "all", .members = members3 },
-        Group{ .gid = 100000, .name = "service-account", .members = members2 },
+        try Group.init(allocator, 0, "root", members0),
+        try Group.init(allocator, 128, "vidmantas", members1),
+        try Group.init(allocator, 9999, "all", members3),
+        try Group.init(allocator, 100000, "service-account", members2),
     };
 
     return try Corpus.init(allocator, users[0..], groups[0..]);
diff --git a/lib/DB.zig b/lib/DB.zig
index dff0566..c7ec2a6 100644
--- a/lib/DB.zig
+++ b/lib/DB.zig
@@ -15,6 +15,7 @@ const pad = @import("padding.zig");
 const compress = @import("compress.zig");
 const PackedUser = @import("PackedUser.zig");
 const User = @import("User.zig");
+const CGroup = @import("CGroup.zig");
 const Group = @import("Group.zig");
 const PackedGroup = @import("PackedGroup.zig");
 const GroupStored = PackedGroup.GroupStored;
@@ -219,10 +220,12 @@ pub fn fromBytes(buf: []align(8) const u8) InvalidHeader!DB {
 }
 
 const GroupMemberNames = struct {
+    _buf: []u8,
     arr: [:null]const ?[*:0]const u8,
 
     pub fn deinit(self: *GroupMemberNames, allocator: Allocator) void {
-        allocator.free(self.arr[0]);
+        if (self._buf.len == 0) return;
+        allocator.free(self._buf);
         allocator.free(self.arr);
     }
 };
@@ -236,22 +239,26 @@ fn groupMemberNames(
 ) error{OutOfMemory}!GroupMemberNames {
     const v = compress.uvarintMust(self.groupmembers[offset..]);
     const total_members_len = v.value;
-    offset += v.bytes_read;
-    var vit = compress.VarintSliceIteratorMust(self.groupmembers[offset..]);
+    const offset2 = offset + v.bytes_read;
+    var vit = compress.VarintSliceIteratorMust(self.groupmembers[offset2..]);
     const num_members = vit.remaining;
-    if (num_members == 0) return null;
+    if (num_members == 0)
+        return GroupMemberNames{
+            ._buf = &[0]u8{},
+            .arr = &[1:null]?[*:0]const u8{null},
+        };
 
     // TODO (zig 0.10+) make result type sentinel-aware and stop
     // the terminating-null-pointer-dancing.
-    var result = try allocator.alloc(?[:0]const u8, num_members + 1);
-    errdefer allocator.free(result);
-    result.len = num_members + 1;
-    result[num_members] = null;
-    result.len = num_members;
+    var arr = try allocator.alloc(?[*:0]const u8, num_members + 1);
+    errdefer allocator.free(arr);
+    arr.len = num_members + 1;
+    arr[num_members] = null;
+    arr.len = num_members;
 
     var buf = try allocator.alloc(u8, total_members_len + num_members);
     errdefer allocator.free(buf);
-    var it = compress.DeltaCompressionIterator(&vit);
+    var it = compress.DeltaDecompressionIterator(&vit);
     var i: usize = 0;
     while (it.nextMust()) |member_offset| : (i += 1) {
         const entry = PackedUser.fromBytes(self.users[member_offset..]);
@@ -260,9 +267,9 @@ fn groupMemberNames(
         buf.len += name.len + 1;
         mem.copy(u8, buf[old_len..], name);
         buf[buf.len - 1] = 0;
-        result[i] = buf[old_len..buf.len :0];
+        arr[i] = buf[old_len..buf.len :0];
     }
-    return GroupMemberNames{ .arr = result };
+    return GroupMemberNames{ ._buf = buf, .arr = arr };
 }
 
 // getgrtnam returns a Group entry by name. The Group must be
@@ -271,7 +278,7 @@ fn getgrnam(
     self: *const DB,
     allocator: Allocator,
     name: []const u8,
-) error{OutOfMemory}!?Group {
+) error{OutOfMemory}!?CGroup {
     const idx = bdz.search(self.bdz_groupname, name);
     const offset = self.idx_groupname2group[idx];
     const group = PackedGroup.fromBytes(self.groups[offset..]).group;
@@ -283,7 +290,7 @@ fn getgrnam(
     const namez = try allocator.dupeZ(u8, name);
     errdefer allocator.free(namez);
 
-    return Group{
+    return CGroup{
         .name = namez,
         .gid = group.gid(),
         .members = members.arr,
diff --git a/lib/Group.zig b/lib/Group.zig
index c71180a..47ed53b 100644
--- a/lib/Group.zig
+++ b/lib/Group.zig
@@ -2,67 +2,56 @@ const std = @import("std");
 
 const mem = std.mem;
 const Allocator = mem.Allocator;
-
 const Group = @This();
 
 gid: u32,
-name: [:0]const u8,
-// should be [:null]const ?[:0]const u8, but it crashes the compiler. See
-// https://github.com/ziglang/zig/issues/7517.
-// members[members.len] is always null for cloned groups. Once the bug
-// in the compiler is fixed, we should update the return type here.
-members: [:null]const ?[*:0]const u8,
+name: []const u8,
+members: []align(1) const []const u8,
 
-// storage of name + members
+// storage of name, members and members strings. for no particular reason.
+// Everything (name, members, member strings) could be allocated separately
+// (one extreme) and only once (another extreme). For some reason I chose the
+// right extreme, but it doesn't have to be this way.
 _buf: []const u8,
 
-pub fn new(
+pub fn init(
     allocator: Allocator,
     gid: u32,
     name: []const u8,
-    members: []const []const u8,
+    members: []align(1) const []const u8,
 ) error{OutOfMemory}!Group {
-    const buf_len = blk: {
+    const buf_len = @sizeOf([]const u8) * members.len + name.len + blk: {
         var sum: usize = 0;
         for (members) |member| sum += member.len;
+        std.debug.print("\nsum: {d}\n", .{sum});
         break :blk @intCast(u32, sum);
     };
-    _ = buf_len;
-    _ = allocator;
-    _ = gid;
-    _ = name;
-    _ = members;
-    return error.OutOfMemory;
-}
-
-pub fn clone(self: *const Group, allocator: Allocator) error{OutOfMemory}!Group {
-    var members = try allocator.allocSentinel(?[*:0]const u8, self.members.len, null);
-    errdefer allocator.free(members);
-
-    var buf = try allocator.alloc(u8, self._buf.len);
+    var buf = try allocator.alloc(u8, buf_len);
     errdefer allocator.free(buf);
-    mem.copy(u8, buf, self._buf);
-
-    const our_begin = @ptrToInt(members.ptr);
-    const their_begin = @ptrToInt(self.members.ptr);
-    for (self.members) |*name_ptr, i| {
-        const offset = @ptrToInt(name_ptr) - their_begin;
-        members[i] = @intToPtr([*:0]const u8, our_begin + offset);
+    var ptr_end = @sizeOf([]const u8) * members.len;
+    var members_ptr = mem.bytesAsSlice([]const u8, buf[0..ptr_end]);
+    var start: usize = name.len;
+    for (members) |member, i| {
+        mem.copy(u8, buf[start..], member);
+        members_ptr[i] = buf[start .. start + member.len];
+        start += member.len;
     }
-
+    mem.copy(u8, buf[start..], name);
     return Group{
-        .gid = self.gid,
-        .name = buf[0..self.name.len],
-        .members = members[0.. :null],
+        .gid = gid,
+        .name = buf[start .. start + name.len],
+        .members = members_ptr,
         ._buf = buf,
     };
 }
 
+// This could be made more efficient, but clone() is never in the hot path.
+pub fn clone(self: *const Group, allocator: Allocator) error{OutOfMemory}!Group {
+    return init(allocator, self.gid, self.name, self.members);
+}
+
 pub fn deinit(self: *Group, allocator: Allocator) void {
-    allocator.free(self.name);
-    if (self.members[0]) |firstmember|
-        allocator.free(firstmember);
-    allocator.free(self.members);
+    allocator.free(self._buf);
     self.* = undefined;
 }
 
@@ -73,11 +62,7 @@ test "Group.clone" {
     var member1 = mem.sliceTo(try testing.allocator.dupeZ(u8, "member1"), 0);
     defer testing.allocator.free(member1);
 
-    var group = Group{
-        .gid = 1,
-        .name = "foo",
-        .members = &[_:null]?[*:0]const u8{ member1, "member2" },
-    };
+    var group = try init(testing.allocator, 1, "foo", &[_][]const u8{ member1, "member2" });
 
     var cloned = try group.clone(testing.allocator);
     defer cloned.deinit(testing.allocator);
@@ -87,5 +72,5 @@ test "Group.clone" {
     member1[0] = 'x';
     try testing.expectEqual(cloned.gid, 1);
     try testing.expectEqualSlices(u8, cloned.name, "foo");
-    //try testing.expectEqualSlices(u8, @as([*:0]const u8, cloned.members[0].?), "member1");
+    try testing.expectEqualSlices(u8, cloned.members[0], "member1");
 }
diff --git a/lib/compress.zig b/lib/compress.zig
index 322eb8c..c792815 100644
--- a/lib/compress.zig
+++ b/lib/compress.zig
@@ -166,6 +166,12 @@ const deltaDecompressionIterator = struct {
     pub fn remaining(self: *const deltaDecompressionIterator) usize {
         return self.vit.remaining;
     }
+
+    pub fn nextMust(self: *deltaDecompressionIterator) ?u64 {
+        return self.next() catch |err| switch (err) {
+            error.Overflow => unreachable,
+        };
+    }
 };
 
 pub fn DeltaDecompressionIterator(vit: *varintSliceIterator) deltaDecompressionIterator {