macho: migrate InternalObject and Dylib

3 files changed, 778 insertions, 344 deletions

diff --git a/src/link/MachO.zig b/src/link/MachO.zig
index 99424b6f40..9f7a306a74 100644
--- a/src/link/MachO.zig
+++ b/src/link/MachO.zig
@@ -3823,145 +3823,6 @@ pub fn getFileHandle(self: MachO, index: File.HandleIndex) File.Handle {
     return self.file_handles.items[index];
 }
 
-pub fn addAtom(self: *MachO) error{OutOfMemory}!Atom.Index {
-    const index = @as(Atom.Index, @intCast(self.atoms.items.len));
-    const atom = try self.atoms.addOne(self.base.comp.gpa);
-    atom.* = .{};
-    return index;
-}
-
-pub fn getAtom(self: *MachO, index: Atom.Index) ?*Atom {
-    if (index == 0) return null;
-    assert(index < self.atoms.items.len);
-    return &self.atoms.items[index];
-}
-
-pub fn addAtomExtra(self: *MachO, extra: Atom.Extra) !u32 {
-    const fields = @typeInfo(Atom.Extra).Struct.fields;
-    try self.atoms_extra.ensureUnusedCapacity(self.base.comp.gpa, fields.len);
-    return self.addAtomExtraAssumeCapacity(extra);
-}
-
-pub fn addAtomExtraAssumeCapacity(self: *MachO, extra: Atom.Extra) u32 {
-    const index = @as(u32, @intCast(self.atoms_extra.items.len));
-    const fields = @typeInfo(Atom.Extra).Struct.fields;
-    inline for (fields) |field| {
-        self.atoms_extra.appendAssumeCapacity(switch (field.type) {
-            u32 => @field(extra, field.name),
-            else => @compileError("bad field type"),
-        });
-    }
-    return index;
-}
-
-pub fn getAtomExtra(self: *MachO, index: u32) ?Atom.Extra {
-    if (index == 0) return null;
-    const fields = @typeInfo(Atom.Extra).Struct.fields;
-    var i: usize = index;
-    var result: Atom.Extra = undefined;
-    inline for (fields) |field| {
-        @field(result, field.name) = switch (field.type) {
-            u32 => self.atoms_extra.items[i],
-            else => @compileError("bad field type"),
-        };
-        i += 1;
-    }
-    return result;
-}
-
-pub fn setAtomExtra(self: *MachO, index: u32, extra: Atom.Extra) void {
-    assert(index > 0);
-    const fields = @typeInfo(Atom.Extra).Struct.fields;
-    inline for (fields, 0..) |field, i| {
-        self.atoms_extra.items[index + i] = switch (field.type) {
-            u32 => @field(extra, field.name),
-            else => @compileError("bad field type"),
-        };
-    }
-}
-
-pub fn addSymbol(self: *MachO) !Symbol.Index {
-    const index = @as(Symbol.Index, @intCast(self.symbols.items.len));
-    const symbol = try self.symbols.addOne(self.base.comp.gpa);
-    symbol.* = .{};
-    return index;
-}
-
-pub fn getSymbol(self: *MachO, index: Symbol.Index) *Symbol {
-    assert(index < self.symbols.items.len);
-    return &self.symbols.items[index];
-}
-
-pub fn addSymbolExtra(self: *MachO, extra: Symbol.Extra) !u32 {
-    const fields = @typeInfo(Symbol.Extra).Struct.fields;
-    try self.symbols_extra.ensureUnusedCapacity(self.base.comp.gpa, fields.len);
-    return self.addSymbolExtraAssumeCapacity(extra);
-}
-
-pub fn addSymbolExtraAssumeCapacity(self: *MachO, extra: Symbol.Extra) u32 {
-    const index = @as(u32, @intCast(self.symbols_extra.items.len));
-    const fields = @typeInfo(Symbol.Extra).Struct.fields;
-    inline for (fields) |field| {
-        self.symbols_extra.appendAssumeCapacity(switch (field.type) {
-            u32 => @field(extra, field.name),
-            else => @compileError("bad field type"),
-        });
-    }
-    return index;
-}
-
-pub fn getSymbolExtra(self: MachO, index: u32) ?Symbol.Extra {
-    if (index == 0) return null;
-    const fields = @typeInfo(Symbol.Extra).Struct.fields;
-    var i: usize = index;
-    var result: Symbol.Extra = undefined;
-    inline for (fields) |field| {
-        @field(result, field.name) = switch (field.type) {
-            u32 => self.symbols_extra.items[i],
-            else => @compileError("bad field type"),
-        };
-        i += 1;
-    }
-    return result;
-}
-
-pub fn setSymbolExtra(self: *MachO, index: u32, extra: Symbol.Extra) void {
-    assert(index > 0);
-    const fields = @typeInfo(Symbol.Extra).Struct.fields;
-    inline for (fields, 0..) |field, i| {
-        self.symbols_extra.items[index + i] = switch (field.type) {
-            u32 => @field(extra, field.name),
-            else => @compileError("bad field type"),
-        };
-    }
-}
-
-const GetOrCreateGlobalResult = struct {
-    found_existing: bool,
-    index: Symbol.Index,
-};
-
-pub fn getOrCreateGlobal(self: *MachO, off: u32) !GetOrCreateGlobalResult {
-    const gpa = self.base.comp.gpa;
-    const gop = try self.globals.getOrPut(gpa, off);
-    if (!gop.found_existing) {
-        const index = try self.addSymbol();
-        const global = self.getSymbol(index);
-        global.name = off;
-        global.flags.global = true;
-        gop.value_ptr.* = index;
-    }
-    return .{
-        .found_existing = gop.found_existing,
-        .index = gop.value_ptr.*,
-    };
-}
-
-pub fn getGlobalByName(self: *MachO, name: []const u8) ?Symbol.Index {
-    const off = self.strings.getOffset(name) orelse return null;
-    return self.globals.get(off);
-}
-
 pub fn addThunk(self: *MachO) !Thunk.Index {
     const index = @as(Thunk.Index, @intCast(self.thunks.items.len));
     const thunk = try self.thunks.addOne(self.base.comp.gpa);
diff --git a/src/link/MachO/Dylib.zig b/src/link/MachO/Dylib.zig
index 458b66d433..6bb3056a61 100644
--- a/src/link/MachO/Dylib.zig
+++ b/src/link/MachO/Dylib.zig
@@ -7,6 +7,8 @@ id: ?Id = null,
 ordinal: u16 = 0,
 
 symbols: std.ArrayListUnmanaged(Symbol.Index) = .{},
+symbols_extra: std.ArrayListUnmanaged(u32) = .{},
+globals: std.ArrayListUnmanaged(MachO.SymbolResolver.Index) = .{},
 dependents: std.ArrayListUnmanaged(Id) = .{},
 rpaths: std.StringArrayHashMapUnmanaged(void) = .{},
 umbrella: File.Index = 0,
@@ -37,6 +39,8 @@ pub fn deinit(self: *Dylib, allocator: Allocator) void {
     self.strtab.deinit(allocator);
     if (self.id) |*id| id.deinit(allocator);
     self.symbols.deinit(allocator);
+    self.symbols_extra.deinit(allocator);
+    self.globals.deinit(allocator);
     for (self.dependents.items) |*id| {
         id.deinit(allocator);
     }
@@ -494,13 +498,21 @@ fn addObjCExport(
 pub fn initSymbols(self: *Dylib, macho_file: *MachO) !void {
     const gpa = macho_file.base.comp.gpa;
 
-    try self.symbols.ensureTotalCapacityPrecise(gpa, self.exports.items(.name).len);
-
-    for (self.exports.items(.name)) |noff| {
-        const name = self.getString(noff);
-        const off = try macho_file.strings.insert(gpa, name);
-        const gop = try macho_file.getOrCreateGlobal(off);
-        self.symbols.addOneAssumeCapacity().* = gop.index;
+    const nsyms = self.exports.items(.name).len;
+    try self.symbols.ensureTotalCapacityPrecise(gpa, nsyms);
+    try self.symbols_extra.ensureTotalCapacityPrecise(gpa, nsyms * @sizeOf(Symbol.Extra));
+    try self.globals.ensureTotalCapacityPrecise(gpa, nsyms);
+    self.globals.resize(gpa, nsyms) catch unreachable;
+    @memset(self.globals.items, 0);
+
+    for (self.exports.items(.name), self.exports.items(.flags)) |noff, flags| {
+        const index = self.addSymbolAssumeCapacity();
+        const symbol = &self.symbols.items[index];
+        symbol.name = noff;
+        symbol.extra = self.addSymbolExtraAssumeCapacity(.{});
+        symbol.flags.weak = flags.weak;
+        symbol.flags.tlv = flags.tlv;
+        symbol.visibility = .global;
     }
 }
 
@@ -510,37 +522,31 @@ pub fn resolveSymbols(self: *Dylib, macho_file: *MachO) void {
 
     if (!self.explicit and !self.hoisted) return;
 
-    for (self.symbols.items, self.exports.items(.flags)) |index, flags| {
-        const global = macho_file.getSymbol(index);
+    const gpa = macho_file.base.comp.gpa;
+
+    for (self.exports.items(.flags), self.globals.items, 0..) |flags, *global, i| {
+        const gop = try macho_file.resolver.getOrPut(gpa, .{
+            .index = @intCast(i),
+            .file = self.index,
+        }, macho_file);
+        if (!gop.found_existing) {
+            gop.ref.* = .{ .index = 0, .file = 0 };
+        }
+        global.* = gop.index;
+
+        if (gop.ref.getFile(macho_file) == null) {
+            gop.ref.* = .{ .index = @intCast(i), .file = self.index };
+            continue;
+        }
+
         if (self.asFile().getSymbolRank(.{
             .weak = flags.weak,
-        }) < global.getSymbolRank(macho_file)) {
-            global.value = 0;
-            global.atom = 0;
-            global.nlist_idx = 0;
-            global.file = self.index;
-            global.flags.weak = flags.weak;
-            global.flags.tlv = flags.tlv;
-            global.flags.dyn_ref = false;
-            global.flags.tentative = false;
-            global.visibility = .global;
+        }) < gop.ref.getSymbol(macho_file).?.getSymbolRank(macho_file)) {
+            gop.ref.* = .{ .index = @intCast(i), .file = self.index };
         }
     }
 }
 
-pub fn resetGlobals(self: *Dylib, macho_file: *MachO) void {
-    for (self.symbols.items) |sym_index| {
-        const sym = macho_file.getSymbol(sym_index);
-        const name = sym.name;
-        const global = sym.flags.global;
-        const weak_ref = sym.flags.weak_ref;
-        sym.* = .{};
-        sym.name = name;
-        sym.flags.global = global;
-        sym.flags.weak_ref = weak_ref;
-    }
-}
-
 pub fn isAlive(self: Dylib, macho_file: *MachO) bool {
     if (!macho_file.dead_strip_dylibs) return self.explicit or self.referenced or self.needed;
     return self.referenced or self.needed;
@@ -550,48 +556,52 @@ pub fn markReferenced(self: *Dylib, macho_file: *MachO) void {
     const tracy = trace(@src());
     defer tracy.end();
 
-    for (self.symbols.items) |global_index| {
-        const global = macho_file.getSymbol(global_index);
-        const file_ptr = global.getFile(macho_file) orelse continue;
-        if (file_ptr.getIndex() != self.index) continue;
+    for (0..self.symbols.items.len) |i| {
+        const ref = self.getSymbolRef(@intCast(i), macho_file);
+        const file = ref.getFile(macho_file) orelse continue;
+        if (file.getIndex() != self.index) continue;
+        const global = ref.getSymbol(macho_file).?;
         if (global.isLocal()) continue;
         self.referenced = true;
         break;
     }
 }
 
-pub fn calcSymtabSize(self: *Dylib, macho_file: *MachO) !void {
+pub fn calcSymtabSize(self: *Dylib, macho_file: *MachO) void {
     const tracy = trace(@src());
     defer tracy.end();
 
-    for (self.symbols.items) |global_index| {
-        const global = macho_file.getSymbol(global_index);
-        const file_ptr = global.getFile(macho_file) orelse continue;
-        if (file_ptr.getIndex() != self.index) continue;
-        if (global.isLocal()) continue;
-        assert(global.flags.import);
-        global.flags.output_symtab = true;
-        try global.addExtra(.{ .symtab = self.output_symtab_ctx.nimports }, macho_file);
+    for (self.symbols.items, 0..) |*sym, i| {
+        const ref = self.getSymbolRef(@intCast(i), macho_file);
+        const file = ref.getFile(macho_file) orelse continue;
+        if (file.getIndex() != self.index) continue;
+        if (sym.isLocal()) continue;
+        assert(sym.flags.import);
+        sym.flags.output_symtab = true;
+        sym.addExtra(.{ .symtab = self.output_symtab_ctx.nimports }, macho_file);
         self.output_symtab_ctx.nimports += 1;
-        self.output_symtab_ctx.strsize += @as(u32, @intCast(global.getName(macho_file).len + 1));
+        self.output_symtab_ctx.strsize += @as(u32, @intCast(sym.getName(macho_file).len + 1));
     }
 }
 
-pub fn writeSymtab(self: Dylib, macho_file: *MachO, ctx: anytype) void {
+pub fn writeSymtab(self: Dylib, macho_file: *MachO) void {
     const tracy = trace(@src());
     defer tracy.end();
 
-    for (self.symbols.items) |global_index| {
-        const global = macho_file.getSymbol(global_index);
-        const file = global.getFile(macho_file) orelse continue;
+    var n_strx = self.output_symtab_ctx.stroff;
+    for (self.symbols.items, 0..) |sym, i| {
+        const ref = self.getSymbolRef(@intCast(i), macho_file);
+        const file = ref.getFile(macho_file) orelse continue;
         if (file.getIndex() != self.index) continue;
-        const idx = global.getOutputSymtabIndex(macho_file) orelse continue;
-        const n_strx = @as(u32, @intCast(ctx.strtab.items.len));
-        ctx.strtab.appendSliceAssumeCapacity(global.getName(macho_file));
-        ctx.strtab.appendAssumeCapacity(0);
-        const out_sym = &ctx.symtab.items[idx];
+        const idx = sym.getOutputSymtabIndex(macho_file) orelse continue;
+        const out_sym = &macho_file.symtab.items[idx];
         out_sym.n_strx = n_strx;
-        global.setOutputSym(macho_file, out_sym);
+        sym.setOutputSym(macho_file, out_sym);
+        const name = sym.getName(macho_file);
+        @memcpy(macho_file.strtab.items[n_strx..][0..name.len], name);
+        n_strx += @intCast(name.len);
+        macho_file.strtab.items[n_strx] = 0;
+        n_strx += 1;
     }
 }
 
@@ -605,7 +615,7 @@ fn addString(self: *Dylib, allocator: Allocator, name: []const u8) !u32 {
     return off;
 }
 
-pub inline fn getString(self: Dylib, off: u32) [:0]const u8 {
+pub fn getString(self: Dylib, off: u32) [:0]const u8 {
     assert(off < self.strtab.items.len);
     return mem.sliceTo(@as([*:0]const u8, @ptrCast(self.strtab.items.ptr + off)), 0);
 }
@@ -614,6 +624,66 @@ pub fn asFile(self: *Dylib) File {
     return .{ .dylib = self };
 }
 
+fn addSymbol(self: *Dylib, allocator: Allocator) !Symbol.Index {
+    try self.symbols.ensureUnusedCapacity(allocator, 1);
+    return self.addSymbolAssumeCapacity();
+}
+
+fn addSymbolAssumeCapacity(self: *Dylib) Symbol.Index {
+    const index: Symbol.Index = @intCast(self.symbols.items.len);
+    const symbol = self.symbols.addOneAssumeCapacity();
+    symbol.* = .{ .file = self.index };
+    return index;
+}
+
+pub fn getSymbolRef(self: Dylib, index: Symbol.Index, macho_file: *MachO) MachO.Ref {
+    const global_index = self.globals.items[index];
+    if (macho_file.resolver.get(global_index)) |ref| return ref;
+    return .{ .index = index, .file = self.index };
+}
+
+pub fn addSymbolExtra(self: *Dylib, allocator: Allocator, extra: Symbol.Extra) !u32 {
+    const fields = @typeInfo(Symbol.Extra).Struct.fields;
+    try self.symbols_extra.ensureUnusedCapacity(allocator, fields.len);
+    return self.addSymbolExtraAssumeCapacity(extra);
+}
+
+fn addSymbolExtraAssumeCapacity(self: *Dylib, extra: Symbol.Extra) u32 {
+    const index = @as(u32, @intCast(self.symbols_extra.items.len));
+    const fields = @typeInfo(Symbol.Extra).Struct.fields;
+    inline for (fields) |field| {
+        self.symbols_extra.appendAssumeCapacity(switch (field.type) {
+            u32 => @field(extra, field.name),
+            else => @compileError("bad field type"),
+        });
+    }
+    return index;
+}
+
+pub fn getSymbolExtra(self: Dylib, index: u32) Symbol.Extra {
+    const fields = @typeInfo(Symbol.Extra).Struct.fields;
+    var i: usize = index;
+    var result: Symbol.Extra = undefined;
+    inline for (fields) |field| {
+        @field(result, field.name) = switch (field.type) {
+            u32 => self.symbols_extra.items[i],
+            else => @compileError("bad field type"),
+        };
+        i += 1;
+    }
+    return result;
+}
+
+pub fn setSymbolExtra(self: *Dylib, index: u32, extra: Symbol.Extra) void {
+    const fields = @typeInfo(Symbol.Extra).Struct.fields;
+    inline for (fields, 0..) |field, i| {
+        self.symbols_extra.items[index + i] = switch (field.type) {
+            u32 => @field(extra, field.name),
+            else => @compileError("bad field type"),
+        };
+    }
+}
+
 pub fn format(
     self: *Dylib,
     comptime unused_fmt_string: []const u8,
diff --git a/src/link/MachO/InternalObject.zig b/src/link/MachO/InternalObject.zig
index 83bbb8ee54..2499f01a03 100644
--- a/src/link/MachO/InternalObject.zig
+++ b/src/link/MachO/InternalObject.zig
@@ -1,12 +1,28 @@
 index: File.Index,
 
 sections: std.MultiArrayList(Section) = .{},
-atoms: std.ArrayListUnmanaged(Atom.Index) = .{},
-symbols: std.ArrayListUnmanaged(Symbol.Index) = .{},
+atoms: std.ArrayListUnmanaged(Atom) = .{},
+atoms_indexes: std.ArrayListUnmanaged(Atom.Index) = .{},
+atoms_extra: std.ArrayListUnmanaged(u32) = .{},
+symtab: std.ArrayListUnmanaged(macho.nlist_64) = .{},
+strtab: std.ArrayListUnmanaged(u8) = .{},
+symbols: std.ArrayListUnmanaged(Symbol) = .{},
+symbols_extra: std.ArrayListUnmanaged(u32) = .{},
+globals: std.ArrayListUnmanaged(MachO.SymbolResolver.Index) = .{},
 
 objc_methnames: std.ArrayListUnmanaged(u8) = .{},
 objc_selrefs: [@sizeOf(u64)]u8 = [_]u8{0} ** @sizeOf(u64),
 
+force_undefined: std.ArrayListUnmanaged(Symbol.Index) = .{},
+entry_index: ?Symbol.Index = null,
+dyld_stub_binder_index: ?Symbol.Index = null,
+dyld_private: ?Symbol.Index = null,
+objc_msg_send_index: ?Symbol.Index = null,
+mh_execute_header_index: ?Symbol.Index = null,
+mh_dylib_header_index: ?Symbol.Index = null,
+dso_handle_index: ?Symbol.Index = null,
+boundary_symbols: std.ArrayListUnmanaged(Symbol.Index) = .{},
+
 output_symtab_ctx: MachO.SymtabCtx = .{},
 
 pub fn deinit(self: *InternalObject, allocator: Allocator) void {
@@ -15,39 +31,224 @@ pub fn deinit(self: *InternalObject, allocator: Allocator) void {
     }
     self.sections.deinit(allocator);
     self.atoms.deinit(allocator);
+    self.atoms_indexes.deinit(allocator);
+    self.atoms_extra.deinit(allocator);
+    self.symtab.deinit(allocator);
+    self.strtab.deinit(allocator);
     self.symbols.deinit(allocator);
+    self.symbols_extra.deinit(allocator);
+    self.globals.deinit(allocator);
     self.objc_methnames.deinit(allocator);
+    self.force_undefined.deinit(allocator);
+    self.boundary_symbols.deinit(allocator);
+}
+
+pub fn init(self: *InternalObject, allocator: Allocator) !void {
+    // Atom at index 0 is reserved as null atom.
+    try self.atoms.append(allocator, .{});
+    try self.atoms_extra.append(allocator, 0);
+    // Null byte in strtab
+    try self.strtab.append(allocator, 0);
 }
 
-pub fn addSymbol(self: *InternalObject, name: [:0]const u8, macho_file: *MachO) !Symbol.Index {
+pub fn initSymbols(self: *InternalObject, macho_file: *MachO) !void {
+    const createSymbol = struct {
+        fn createSymbol(obj: *InternalObject, name: u32, args: struct {
+            type: u8 = macho.N_UNDF | macho.N_EXT,
+            desc: u16 = 0,
+        }) Symbol.Index {
+            const index = obj.addSymbolAssumeCapacity();
+            const symbol = &obj.symbols.items[index];
+            symbol.name = name;
+            symbol.extra = obj.addSymbolExtraAssumeCapacity(.{});
+            symbol.flags.dyn_ref = args.desc & macho.REFERENCED_DYNAMICALLY != 0;
+            symbol.visibility = if (args.type & macho.N_EXT != 0) blk: {
+                break :blk if (args.type & macho.N_PEXT != 0) .hidden else .global;
+            } else .local;
+
+            const nlist_idx: u32 = @intCast(obj.symtab.items.len);
+            const nlist = obj.symtab.addOneAssumeCapacity();
+            nlist.* = .{
+                .n_strx = name,
+                .n_type = args.type,
+                .n_sect = 0,
+                .n_desc = args.desc,
+                .n_value = 0,
+            };
+            symbol.nlist_idx = nlist_idx;
+            return index;
+        }
+    }.createSymbol;
+
     const gpa = macho_file.base.comp.gpa;
-    try self.symbols.ensureUnusedCapacity(gpa, 1);
-    const off = try macho_file.strings.insert(gpa, name);
-    const gop = try macho_file.getOrCreateGlobal(off);
-    self.symbols.addOneAssumeCapacity().* = gop.index;
-    const sym = macho_file.getSymbol(gop.index);
-    sym.file = self.index;
-    sym.value = 0;
-    sym.atom = 0;
-    sym.nlist_idx = 0;
-    sym.flags = .{ .global = true };
-    return gop.index;
+    var nsyms = macho_file.base.comp.force_undefined_symbols.keys().len;
+    nsyms += 1; // dyld_stub_binder
+    nsyms += 1; // _objc_msgSend
+    if (!macho_file.base.isDynLib()) {
+        nsyms += 1; // entry
+        nsyms += 1; // __mh_execute_header
+    } else {
+        nsyms += 1; // __mh_dylib_header
+    }
+    nsyms += 1; // ___dso_handle
+    nsyms += 1; // dyld_private
+
+    try self.symbols.ensureTotalCapacityPrecise(gpa, nsyms);
+    try self.symbols_extra.ensureTotalCapacityPrecise(gpa, nsyms * @sizeOf(Symbol.Extra));
+    try self.symtab.ensureTotalCapacityPrecise(gpa, nsyms);
+    try self.globals.ensureTotalCapacityPrecise(gpa, nsyms);
+    self.globals.resize(gpa, nsyms) catch unreachable;
+    @memset(self.globals.items, 0);
+
+    try self.force_undefined.ensureTotalCapacityPrecise(gpa, macho_file.base.comp.force_undefined_symbols.keys().len);
+    for (macho_file.base.comp.force_undefined_symbols.keys()) |name| {
+        self.force_undefined.addOneAssumeCapacity().* = createSymbol(self, try self.addString(gpa, name), .{});
+    }
+
+    self.dyld_stub_binder_index = createSymbol(self, try self.addString(gpa, "dyld_stub_binder"), .{});
+    self.objc_msg_send_index = createSymbol(self, try self.addString(gpa, "_objc_msgSend"), .{});
+
+    if (!macho_file.base.isDynLib()) {
+        self.entry_index = createSymbol(self, try self.addString(gpa, macho_file.entry_name orelse "_main"), .{});
+        self.mh_execute_header_index = createSymbol(self, try self.addString(gpa, "__mh_execute_header"), .{
+            .type = macho.N_SECT | macho.N_EXT,
+            .desc = macho.REFERENCED_DYNAMICALLY,
+        });
+    } else {
+        self.mh_dylib_header_index = createSymbol(self, try self.addString(gpa, "__mh_dylib_header"), .{
+            .type = macho.N_SECT | macho.N_EXT,
+        });
+    }
+
+    self.dso_handle_index = createSymbol(self, try self.addString(gpa, "___dso_handle"), .{
+        .type = macho.N_SECT | macho.N_EXT,
+    });
+    self.dyld_private_index = createSymbol(self, try self.addString(gpa, "dyld_private"), .{
+        .type = macho.N_SECT,
+    });
 }
 
-/// Creates a fake input sections __TEXT,__objc_methname and __DATA,__objc_selrefs.
-pub fn addObjcMsgsendSections(self: *InternalObject, sym_name: []const u8, macho_file: *MachO) !Atom.Index {
-    const methname_atom_index = try self.addObjcMethnameSection(sym_name, macho_file);
-    return try self.addObjcSelrefsSection(methname_atom_index, macho_file);
+pub fn resolveSymbols(self: *InternalObject, macho_file: *MachO) !void {
+    const tracy = trace(@src());
+    defer tracy.end();
+
+    const gpa = macho_file.base.comp.gpa;
+
+    for (self.symtab.items, self.globals.items, 0..) |nlist, *global, i| {
+        const gop = try macho_file.resolver.getOrPut(gpa, .{
+            .index = @intCast(i),
+            .file = self.index,
+        }, macho_file);
+        if (!gop.found_existing) {
+            gop.ref.* = .{ .index = 0, .file = 0 };
+        }
+        global.* = gop.index;
+
+        if (nlist.undf()) continue;
+        if (gop.ref.getFile(macho_file) == null) {
+            gop.ref.* = .{ .index = @intCast(i), .file = self.index };
+            continue;
+        }
+
+        if (self.asFile().getSymbolRank(.{
+            .archive = false,
+            .weak = false,
+            .tentative = false,
+        }) < gop.ref.getSymbol(macho_file).?.getSymbolRank(macho_file)) {
+            gop.ref.* = .{ .index = @intCast(i), .file = self.index };
+        }
+    }
 }
 
-fn addObjcMethnameSection(self: *InternalObject, methname: []const u8, macho_file: *MachO) !Atom.Index {
+pub fn resolveBoundarySymbols(self: *InternalObject, macho_file: *MachO) !void {
+    const tracy = trace(@src());
+    defer tracy.end();
+
     const gpa = macho_file.base.comp.gpa;
-    const atom_index = try macho_file.addAtom();
-    try self.atoms.append(gpa, atom_index);
+    var boundary_symbols = std.StringArrayHashMap(MachO.Ref).init(gpa);
+    defer boundary_symbols.deinit();
+
+    for (macho_file.objects.items) |index| {
+        const object = macho_file.getFile(index).?.object;
+        for (object.symbols.items, 0..) |sym, i| {
+            const nlist = object.symtab.items(.nlist)[i];
+            if (!nlist.undf() or !nlist.ext()) continue;
+            const ref = object.getSymbolRef(@intCast(i), macho_file);
+            if (ref.getFile(macho_file) != null) continue;
+            const name = sym.getName(macho_file);
+            if (mem.startsWith(u8, name, "segment$start$") or
+                mem.startsWith(u8, name, "segment$stop$") or
+                mem.startsWith(u8, name, "section$start$") or
+                mem.startsWith(u8, name, "section$stop$"))
+            {
+                const gop = try boundary_symbols.getOrPut(name);
+                if (!gop.found_existing) {
+                    gop.value_ptr.* = .{ .index = @intCast(i), .file = index };
+                }
+            }
+        }
+    }
+
+    const nsyms = boundary_symbols.values().len;
+    try self.boundary_symbols.ensureTotalCapacityPrecise(gpa, nsyms);
+    try self.symbols.ensureUnusedCapacity(gpa, nsyms);
+    try self.symtab.ensureUnusedCapacity(gpa, nsyms);
+    try self.symbols_extra.ensureUnusedCapacity(gpa, nsyms * @sizeOf(Symbol.Extra));
+    try self.globals.ensureUnusedCapacity(gpa, nsyms);
+
+    for (boundary_symbols.keys(), boundary_symbols.values()) |name, ref| {
+        const name_off = try self.addString(gpa, name);
+        const sym_index = self.addSymbolAssumeCapacity();
+        self.boundary_symbols.appendAssumeCapacity(sym_index);
+        const sym = &self.symbols.items[sym_index];
+        sym.name = name_off;
+        sym.visibility = .local;
+        const nlist_idx: u32 = @intCast(self.symtab.items.len);
+        const nlist = self.symtab.addOneAssumeCapacity();
+        nlist.* = .{
+            .n_strx = name_off.pos,
+            .n_type = macho.N_SECT,
+            .n_sect = 0,
+            .n_desc = 0,
+            .n_value = 0,
+        };
+        sym.nlist_idx = nlist_idx;
+        sym.extra = self.addSymbolExtraAssumeCapacity(.{});
+
+        const idx = ref.getFile(macho_file).?.object.globals.items[ref.index];
+        self.globals.addOneAssumeCapacity().* = idx;
+        macho_file.resolver.values.items[idx - 1] = .{ .index = sym_index, .file = self.index };
+    }
+}
+
+pub fn markLive(self: *InternalObject, macho_file: *MachO) void {
+    const tracy = trace(@src());
+    defer tracy.end();
+
+    for (0..self.symbols.items.len) |i| {
+        const nlist = self.symtab.items[i];
+        if (!nlist.ext()) continue;
+
+        const ref = self.getSymbolRef(@intCast(i), macho_file);
+        const file = ref.getFile(macho_file) orelse continue;
+        if (file == .object and !file.object.alive) {
+            file.object.alive = true;
+            file.object.markLive(macho_file);
+        }
+    }
+}
 
-    const atom = macho_file.getAtom(atom_index).?;
-    atom.atom_index = atom_index;
-    atom.file = self.index;
+/// Creates a fake input sections __TEXT,__objc_methname and __DATA,__objc_selrefs.
+pub fn addObjcMsgsendSections(self: *InternalObject, sym_name: []const u8, macho_file: *MachO) !Symbol.Index {
+    const methname_sym_index = try self.addObjcMethnameSection(sym_name, macho_file);
+    return try self.addObjcSelrefsSection(methname_sym_index, macho_file);
+}
+
+fn addObjcMethnameSection(self: *InternalObject, methname: []const u8, macho_file: *MachO) !Symbol.Index {
+    const gpa = macho_file.base.comp.gpa;
+    const atom_index = try self.addAtom(gpa);
+    try self.atoms_indexes.append(gpa, atom_index);
+    const atom = self.getAtom(atom_index).?;
     atom.size = methname.len + 1;
     atom.alignment = .@"1";
 
@@ -63,19 +264,34 @@ fn addObjcMethnameSection(self: *InternalObject, methname: []const u8, macho_fil
     try self.objc_methnames.ensureUnusedCapacity(gpa, methname.len + 1);
     self.objc_methnames.writer(gpa).print("{s}\x00", .{methname}) catch unreachable;
 
+    const name_str = try self.addString(gpa, "ltmp");
+    const sym_index = try self.addSymbol(gpa);
+    const sym = &self.symbols.items[sym_index];
+    sym.name = name_str;
+    sym.atom_ref = .{ .index = atom_index, .file = self.index };
+    sym.extra = try self.addSymbolExtra(gpa, .{});
+    const nlist_idx: u32 = @intCast(self.symtab.items.len);
+    const nlist = try self.symtab.addOne(gpa);
+    nlist.* = .{
+        .n_strx = name_str.pos,
+        .n_type = macho.N_SECT,
+        .n_sect = @intCast(n_sect + 1),
+        .n_desc = 0,
+        .n_value = 0,
+    };
+    sym.nlist_idx = nlist_idx;
+    try self.globals.append(gpa, 0);
+
     return atom_index;
 }
 
-fn addObjcSelrefsSection(self: *InternalObject, methname_atom_index: Atom.Index, macho_file: *MachO) !Atom.Index {
-    const gpa = macho_file.base.comp.gpa;
-    const atom_index = try macho_file.addAtom();
-    try self.atoms.append(gpa, atom_index);
-
-    const atom = macho_file.getAtom(atom_index).?;
-    atom.atom_index = atom_index;
-    atom.file = self.index;
+fn addObjcSelrefsSection(self: *InternalObject, methname_sym_index: Symbol.Index, macho_file: *MachO) !Symbol.Index {
+    const gpa = macho_file.base.allocator;
+    const atom_index = try self.addAtom(gpa);
+    try self.atoms_indexes.append(gpa, atom_index);
+    const atom = self.getAtom(atom_index).?;
     atom.size = @sizeOf(u64);
-    atom.alignment = .@"8";
+    atom.alignment = 3;
 
     const n_sect = try self.addSection(gpa, "__DATA", "__objc_selrefs");
     const sect = &self.sections.items(.header)[n_sect];
@@ -89,9 +305,9 @@ fn addObjcSelrefsSection(self: *InternalObject, methname_atom_index: Atom.Index,
     const relocs = &self.sections.items(.relocs)[n_sect];
     try relocs.ensureUnusedCapacity(gpa, 1);
     relocs.appendAssumeCapacity(.{
-        .tag = .local,
+        .tag = .@"extern",
         .offset = 0,
-        .target = methname_atom_index,
+        .target = methname_sym_index,
         .addend = 0,
         .type = .unsigned,
         .meta = .{
@@ -101,139 +317,283 @@ fn addObjcSelrefsSection(self: *InternalObject, methname_atom_index: Atom.Index,
             .has_subtractor = false,
         },
     });
-    try atom.addExtra(.{ .rel_index = 0, .rel_count = 1 }, macho_file);
-    atom.flags.relocs = true;
+    atom.addExtra(.{ .rel_index = 0, .rel_count = 1 }, macho_file);
+
+    const sym_index = try self.addSymbol(gpa);
+    const sym = &self.symbols.items[sym_index];
+    sym.atom_ref = .{ .index = atom_index, .file = self.index };
+    sym.extra = try self.addSymbolExtra(gpa, .{});
+    const nlist_idx: u32 = @intCast(self.symtab.items.len);
+    const nlist = try self.symtab.addOne(gpa);
+    nlist.* = .{
+        .n_strx = 0,
+        .n_type = macho.N_SECT,
+        .n_sect = @intCast(n_sect + 1),
+        .n_desc = 0,
+        .n_value = 0,
+    };
+    sym.nlist_idx = nlist_idx;
+    try self.globals.append(gpa, 0);
+    atom.addExtra(.{ .literal_symbol_index = sym_index }, macho_file);
 
-    return atom_index;
+    return sym_index;
+}
+
+pub fn resolveObjcMsgSendSymbols(self: *InternalObject, macho_file: *MachO) !void {
+    const tracy = trace(@src());
+    defer tracy.end();
+
+    const gpa = macho_file.base.comp.gpa;
+
+    var objc_msgsend_syms = std.StringArrayHashMap(MachO.Ref).init(gpa);
+    defer objc_msgsend_syms.deinit();
+
+    for (macho_file.objects.items) |index| {
+        const object = macho_file.getFile(index).?.object;
+
+        for (object.symbols.items, 0..) |sym, i| {
+            const nlist = object.symtab.items(.nlist)[i];
+            if (!nlist.ext()) continue;
+            if (!nlist.undf()) continue;
+
+            const ref = object.getSymbolRef(@intCast(i), macho_file);
+            if (ref.getFile(macho_file) != null) continue;
+
+            const name = sym.getName(macho_file);
+            if (mem.startsWith(u8, name, "_objc_msgSend$")) {
+                const gop = try objc_msgsend_syms.getOrPut(name);
+                if (!gop.found_existing) {
+                    gop.value_ptr.* = .{ .index = @intCast(i), .file = index };
+                }
+            }
+        }
+    }
+
+    for (objc_msgsend_syms.keys(), objc_msgsend_syms.values()) |sym_name, ref| {
+        const name = MachO.eatPrefix(sym_name, "_objc_msgSend$").?;
+        const selrefs_index = try self.addObjcMsgsendSections(name, macho_file);
+
+        const name_off = try self.addString(gpa, sym_name);
+        const sym_index = try self.addSymbol(gpa);
+        const sym = &self.symbols.items[sym_index];
+        sym.name = name_off;
+        sym.visibility = .hidden;
+        const nlist_idx: u32 = @intCast(self.symtab.items.len);
+        const nlist = try self.symtab.addOne(gpa);
+        nlist.* = .{
+            .n_strx = name_off,
+            .n_type = macho.N_SECT | macho.N_EXT | macho.N_PEXT,
+            .n_sect = 0,
+            .n_desc = 0,
+            .n_value = 0,
+        };
+        sym.nlist_idx = nlist_idx;
+        sym.extra = try self.addSymbolExtra(gpa, .{ .objc_selrefs = selrefs_index });
+        sym.setSectionFlags(.{ .objc_stubs = true });
+
+        const idx = ref.getFile(macho_file).?.object.globals.items[ref.index];
+        try self.globals.append(gpa, idx);
+        macho_file.resolver.values.items[idx - 1] = .{ .index = sym_index, .file = self.index };
+    }
 }
 
-pub fn resolveLiterals(self: InternalObject, lp: *MachO.LiteralPool, macho_file: *MachO) !void {
+pub fn resolveLiterals(self: *InternalObject, lp: *MachO.LiteralPool, macho_file: *MachO) !void {
+    const tracy = trace(@src());
+    defer tracy.end();
+
     const gpa = macho_file.base.comp.gpa;
 
     var buffer = std.ArrayList(u8).init(gpa);
     defer buffer.deinit();
 
     const slice = self.sections.slice();
-    for (slice.items(.header), self.atoms.items, 0..) |header, atom_index, n_sect| {
-        if (Object.isCstringLiteral(header) or Object.isFixedSizeLiteral(header)) {
-            const data = try self.getSectionData(@intCast(n_sect));
-            const atom = macho_file.getAtom(atom_index).?;
-            const res = try lp.insert(gpa, header.type(), data);
-            if (!res.found_existing) {
-                res.atom.* = atom_index;
-            }
-            atom.flags.literal_pool = true;
-            try atom.addExtra(.{ .literal_index = res.index }, macho_file);
-        } else if (Object.isPtrLiteral(header)) {
-            const atom = macho_file.getAtom(atom_index).?;
-            const relocs = atom.getRelocs(macho_file);
-            assert(relocs.len == 1);
-            const rel = relocs[0];
-            assert(rel.tag == .local);
-            const target = macho_file.getAtom(rel.target).?;
-            const addend = std.math.cast(u32, rel.addend) orelse return error.Overflow;
-            const target_size = std.math.cast(usize, target.size) orelse return error.Overflow;
-            try buffer.ensureUnusedCapacity(target_size);
-            buffer.resize(target_size) catch unreachable;
-            try target.getData(macho_file, buffer.items);
-            const res = try lp.insert(gpa, header.type(), buffer.items[addend..]);
-            buffer.clearRetainingCapacity();
-            if (!res.found_existing) {
-                res.atom.* = atom_index;
-            }
-            atom.flags.literal_pool = true;
-            try atom.addExtra(.{ .literal_index = res.index }, macho_file);
+    for (slice.items(.header), self.getAtoms()) |header, atom_index| {
+        if (!Object.isPtrLiteral(header)) continue;
+        const atom = self.getAtom(atom_index).?;
+        const relocs = atom.getRelocs(macho_file);
+        assert(relocs.len == 1);
+        const rel = relocs[0];
+        assert(rel.tag == .@"extern");
+        const target = rel.getTargetSymbol(atom.*, macho_file).getAtom(macho_file).?;
+        try buffer.ensureUnusedCapacity(target.size);
+        buffer.resize(target.size) catch unreachable;
+        @memcpy(buffer.items, self.getSectionData(target.n_sect));
+        const res = try lp.insert(gpa, header.type(), buffer.items);
+        buffer.clearRetainingCapacity();
+        if (!res.found_existing) {
+            res.ref.* = .{ .index = atom.getExtra(macho_file).literal_symbol_index, .file = self.index };
+        } else {
+            const lp_sym = lp.getSymbol(res.index, macho_file);
+            const lp_atom = lp_sym.getAtom(macho_file).?;
+            lp_atom.alignment = @max(lp_atom.alignment, atom.alignment);
+            atom.flags.alive = false;
         }
+        atom.addExtra(.{ .literal_pool_index = res.index }, macho_file);
     }
 }
 
-pub fn dedupLiterals(self: InternalObject, lp: MachO.LiteralPool, macho_file: *MachO) void {
-    for (self.atoms.items) |atom_index| {
-        const atom = macho_file.getAtom(atom_index) orelse continue;
-        if (!atom.flags.alive) continue;
-        if (!atom.flags.relocs) continue;
+pub fn dedupLiterals(self: *InternalObject, lp: MachO.LiteralPool, macho_file: *MachO) void {
+    const tracy = trace(@src());
+    defer tracy.end();
+
+    for (self.getAtoms()) |atom_index| {
+        const atom = self.getAtom(atom_index) orelse continue;
+        if (!atom.alive.load(.seq_cst)) continue;
 
         const relocs = blk: {
-            const extra = atom.getExtra(macho_file).?;
+            const extra = atom.getExtra(macho_file);
             const relocs = self.sections.items(.relocs)[atom.n_sect].items;
             break :blk relocs[extra.rel_index..][0..extra.rel_count];
         };
-        for (relocs) |*rel| switch (rel.tag) {
-            .local => {
-                const target = macho_file.getAtom(rel.target).?;
-                if (target.getLiteralPoolIndex(macho_file)) |lp_index| {
-                    const lp_atom = lp.getAtom(lp_index, macho_file);
-                    if (target.atom_index != lp_atom.atom_index) {
-                        lp_atom.alignment = lp_atom.alignment.max(target.alignment);
-                        target.flags.alive = false;
-                        rel.target = lp_atom.atom_index;
-                    }
-                }
-            },
-            .@"extern" => {
-                const target_sym = rel.getTargetSymbol(macho_file);
-                if (target_sym.getAtom(macho_file)) |target_atom| {
-                    if (target_atom.getLiteralPoolIndex(macho_file)) |lp_index| {
-                        const lp_atom = lp.getAtom(lp_index, macho_file);
-                        if (target_atom.atom_index != lp_atom.atom_index) {
-                            lp_atom.alignment = lp_atom.alignment.max(target_atom.alignment);
-                            target_atom.flags.alive = false;
-                            target_sym.atom = lp_atom.atom_index;
-                        }
-                    }
-                }
-            },
+        for (relocs) |*rel| {
+            if (rel.tag != .@"extern") continue;
+            const target_sym_ref = rel.getTargetSymbolRef(atom.*, macho_file);
+            const file = target_sym_ref.getFile(macho_file) orelse continue;
+            if (file.getIndex() != self.index) continue;
+            const target_sym = target_sym_ref.getSymbol(macho_file).?;
+            const target_atom = target_sym.getAtom(macho_file) orelse continue;
+            if (!Object.isPtrLiteral(target_atom.getInputSection(macho_file))) continue;
+            const lp_index = target_atom.getExtra(macho_file).literal_pool_index;
+            const lp_sym = lp.getSymbol(lp_index, macho_file);
+            const lp_atom_ref = lp_sym.atom_ref;
+            if (target_atom.atom_index != lp_atom_ref.index or target_atom.file != lp_atom_ref.file) {
+                target_sym.atom_ref = lp_atom_ref;
+            }
+        }
+    }
+
+    for (self.symbols.items) |*sym| {
+        if (!sym.getSectionFlags().objc_stubs) continue;
+        const extra = sym.getExtra(macho_file);
+        const file = sym.getFile(macho_file).?;
+        if (file.getIndex() != self.index) continue;
+        const tsym = switch (file) {
+            .dylib => unreachable,
+            inline else => |x| &x.symbols.items[extra.objc_selrefs],
         };
+        const atom = tsym.getAtom(macho_file) orelse continue;
+        if (!Object.isPtrLiteral(atom.getInputSection(macho_file))) continue;
+        const lp_index = atom.getExtra(macho_file).literal_pool_index;
+        const lp_sym = lp.getSymbol(lp_index, macho_file);
+        const lp_atom_ref = lp_sym.atom_ref;
+        if (atom.atom_index != lp_atom_ref.index or atom.file != lp_atom_ref.file) {
+            tsym.atom_ref = lp_atom_ref;
+        }
     }
+}
+
+pub fn scanRelocs(self: *InternalObject, macho_file: *MachO) void {
+    const tracy = trace(@src());
+    defer tracy.end();
 
-    for (self.symbols.items) |sym_index| {
-        const sym = macho_file.getSymbol(sym_index);
-        if (!sym.flags.objc_stubs) continue;
-        var extra = sym.getExtra(macho_file).?;
-        const atom = macho_file.getAtom(extra.objc_selrefs).?;
-        if (atom.getLiteralPoolIndex(macho_file)) |lp_index| {
-            const lp_atom = lp.getAtom(lp_index, macho_file);
-            if (atom.atom_index != lp_atom.atom_index) {
-                lp_atom.alignment = lp_atom.alignment.max(atom.alignment);
-                atom.flags.alive = false;
-                extra.objc_selrefs = lp_atom.atom_index;
-                sym.setExtra(extra, macho_file);
+    if (self.getEntryRef(macho_file)) |ref| {
+        if (ref.getFile(macho_file) != null) {
+            const sym = ref.getSymbol(macho_file).?;
+            if (sym.flags.import) sym.flags.stubs = true;
+        }
+    }
+    if (self.getDyldStubBinderRef(macho_file)) |ref| {
+        if (ref.getFile(macho_file) != null) {
+            const sym = ref.getSymbol(macho_file).?;
+            sym.flags.got = true;
+        }
+    }
+    if (self.getObjcMsgSendRef(macho_file)) |ref| {
+        if (ref.getFile(macho_file) != null) {
+            const sym = ref.getSymbol(macho_file).?;
+            // TODO is it always needed, or only if we are synthesising fast stubs
+            sym.flags.got = true;
+        }
+    }
+}
+
+pub fn allocateSyntheticSymbols(self: *InternalObject, macho_file: *MachO) void {
+    const text_seg = macho_file.getTextSegment();
+
+    if (self.mh_execute_header_index) |index| {
+        const ref = self.getSymbolRef(index, macho_file);
+        if (ref.getFile(macho_file)) |file| {
+            if (file.getIndex() == self.index) {
+                const sym = &self.symbols.items[index];
+                sym.value = text_seg.vmaddr;
+            }
+        }
+    }
+
+    if (macho_file.data_sect_index) |idx| {
+        const sect = macho_file.sections.items(.header)[idx];
+        for (&[_]?Symbol.Index{
+            self.dso_handle_index,
+            self.mh_dylib_header_index,
+            self.dyld_private_index,
+        }) |maybe_index| {
+            if (maybe_index) |index| {
+                const ref = self.getSymbolRef(index, macho_file);
+                if (ref.getFile(macho_file)) |file| {
+                    if (file.getIndex() == self.index) {
+                        const sym = &self.symbols.items[index];
+                        sym.value = sect.addr;
+                        sym.out_n_sect = idx;
+                    }
+                }
             }
         }
     }
 }
 
-pub fn calcSymtabSize(self: *InternalObject, macho_file: *MachO) !void {
-    for (self.symbols.items) |sym_index| {
-        const sym = macho_file.getSymbol(sym_index);
-        if (sym.getFile(macho_file)) |file| if (file.getIndex() != self.index) continue;
+pub fn calcSymtabSize(self: *InternalObject, macho_file: *MachO) void {
+    for (self.symbols.items, 0..) |*sym, i| {
+        const ref = self.getSymbolRef(@intCast(i), macho_file);
+        const file = ref.getFile(macho_file) orelse continue;
+        if (file.getIndex() != self.index) continue;
+        if (sym.getName(macho_file).len == 0) continue;
         sym.flags.output_symtab = true;
         if (sym.isLocal()) {
-            try sym.addExtra(.{ .symtab = self.output_symtab_ctx.nlocals }, macho_file);
+            sym.addExtra(.{ .symtab = self.output_symtab_ctx.nlocals }, macho_file);
             self.output_symtab_ctx.nlocals += 1;
         } else if (sym.flags.@"export") {
-            try sym.addExtra(.{ .symtab = self.output_symtab_ctx.nexports }, macho_file);
+            sym.addExtra(.{ .symtab = self.output_symtab_ctx.nexports }, macho_file);
             self.output_symtab_ctx.nexports += 1;
         } else {
             assert(sym.flags.import);
-            try sym.addExtra(.{ .symtab = self.output_symtab_ctx.nimports }, macho_file);
+            sym.addExtra(.{ .symtab = self.output_symtab_ctx.nimports }, macho_file);
             self.output_symtab_ctx.nimports += 1;
         }
         self.output_symtab_ctx.strsize += @as(u32, @intCast(sym.getName(macho_file).len + 1));
     }
 }
 
-pub fn writeSymtab(self: InternalObject, macho_file: *MachO, ctx: anytype) void {
-    for (self.symbols.items) |sym_index| {
-        const sym = macho_file.getSymbol(sym_index);
-        if (sym.getFile(macho_file)) |file| if (file.getIndex() != self.index) continue;
+pub fn writeAtoms(self: *InternalObject, macho_file: *MachO) !void {
+    const tracy = trace(@src());
+    defer tracy.end();
+
+    for (self.getAtoms()) |atom_index| {
+        const atom = self.getAtom(atom_index) orelse continue;
+        if (!atom.alive.load(.seq_cst)) continue;
+        const sect = atom.getInputSection(macho_file);
+        if (sect.isZerofill()) continue;
+        const off = atom.value;
+        const buffer = macho_file.sections.items(.out)[atom.out_n_sect].items[off..][0..atom.size];
+        @memcpy(buffer, self.getSectionData(atom.n_sect));
+        try atom.resolveRelocs(macho_file, buffer);
+    }
+}
+
+pub fn writeSymtab(self: InternalObject, macho_file: *MachO) void {
+    var n_strx = self.output_symtab_ctx.stroff;
+    for (self.symbols.items, 0..) |sym, i| {
+        const ref = self.getSymbolRef(@intCast(i), macho_file);
+        const file = ref.getFile(macho_file) orelse continue;
+        if (file.getIndex() != self.index) continue;
         const idx = sym.getOutputSymtabIndex(macho_file) orelse continue;
-        const n_strx = @as(u32, @intCast(ctx.strtab.items.len));
-        ctx.strtab.appendSliceAssumeCapacity(sym.getName(macho_file));
-        ctx.strtab.appendAssumeCapacity(0);
-        const out_sym = &ctx.symtab.items[idx];
+        const out_sym = &macho_file.symtab.items[idx];
         out_sym.n_strx = n_strx;
         sym.setOutputSym(macho_file, out_sym);
+        const name = sym.getName(macho_file);
+        @memcpy(macho_file.strtab.items[n_strx..][0..name.len], name);
+        n_strx += @intCast(name.len);
+        macho_file.strtab.items[n_strx] = 0;
+        n_strx += 1;
     }
 }
 
@@ -262,32 +622,167 @@ fn getSectionData(self: *const InternalObject, index: u32) error{Overflow}![]con
         @panic("ref to non-existent section");
 }
 
-pub fn getAtomData(self: *const InternalObject, atom: Atom, buffer: []u8) error{Overflow}!void {
-    assert(buffer.len == atom.size);
-    const data = try self.getSectionData(atom.n_sect);
-    const off = std.math.cast(usize, atom.off) orelse return error.Overflow;
-    const size = std.math.cast(usize, atom.size) orelse return error.Overflow;
-    @memcpy(buffer, data[off..][0..size]);
-}
-
-pub fn getAtomRelocs(self: *const InternalObject, atom: Atom, macho_file: *MachO) []const Relocation {
-    if (!atom.flags.relocs) return &[0]Relocation{};
-    const extra = atom.getExtra(macho_file).?;
-    const relocs = self.sections.items(.relocs)[atom.n_sect];
-    return relocs.items[extra.rel_index..][0..extra.rel_count];
+pub fn addString(self: *InternalObject, allocator: Allocator, name: []const u8) !u32 {
+    const off: u32 = @intCast(self.strtab.items.len);
+    try self.strtab.ensureUnusedCapacity(allocator, name.len + 1);
+    self.strtab.appendSliceAssumeCapacity(name);
+    self.strtab.appendAssumeCapacity(0);
+    return off;
 }
 
 pub fn getString(self: InternalObject, off: u32) [:0]const u8 {
-    _ = self;
-    _ = off;
-    // We don't have any local strings for synthetic atoms.
-    return "";
+    assert(off < self.strtab.items.len);
+    return mem.sliceTo(@as([*:0]const u8, @ptrCast(self.strtab.items.ptr + off)), 0);
 }
 
 pub fn asFile(self: *InternalObject) File {
     return .{ .internal = self };
 }
 
+fn addAtom(self: *InternalObject, allocator: Allocator) !Atom.Index {
+    const atom_index: Atom.Index = @intCast(self.atoms.items.len);
+    const atom = try self.atoms.addOne(allocator);
+    atom.* = .{
+        .file = self.index,
+        .atom_index = atom_index,
+        .extra = try self.addAtomExtra(allocator, .{}),
+    };
+    return atom_index;
+}
+
+pub fn getAtom(self: *InternalObject, atom_index: Atom.Index) ?*Atom {
+    if (atom_index == 0) return null;
+    assert(atom_index < self.atoms.items.len);
+    return &self.atoms.items[atom_index];
+}
+
+pub fn getAtoms(self: InternalObject) []const Atom.Index {
+    return self.atoms_indexes.items;
+}
+
+fn addAtomExtra(self: *InternalObject, allocator: Allocator, extra: Atom.Extra) !u32 {
+    const fields = @typeInfo(Atom.Extra).Struct.fields;
+    try self.atoms_extra.ensureUnusedCapacity(allocator, fields.len);
+    return self.addAtomExtraAssumeCapacity(extra);
+}
+
+fn addAtomExtraAssumeCapacity(self: *InternalObject, extra: Atom.Extra) u32 {
+    const index = @as(u32, @intCast(self.atoms_extra.items.len));
+    const fields = @typeInfo(Atom.Extra).Struct.fields;
+    inline for (fields) |field| {
+        self.atoms_extra.appendAssumeCapacity(switch (field.type) {
+            u32 => @field(extra, field.name),
+            else => @compileError("bad field type"),
+        });
+    }
+    return index;
+}
+
+pub fn getAtomExtra(self: InternalObject, index: u32) Atom.Extra {
+    const fields = @typeInfo(Atom.Extra).Struct.fields;
+    var i: usize = index;
+    var result: Atom.Extra = undefined;
+    inline for (fields) |field| {
+        @field(result, field.name) = switch (field.type) {
+            u32 => self.atoms_extra.items[i],
+            else => @compileError("bad field type"),
+        };
+        i += 1;
+    }
+    return result;
+}
+
+pub fn setAtomExtra(self: *InternalObject, index: u32, extra: Atom.Extra) void {
+    assert(index > 0);
+    const fields = @typeInfo(Atom.Extra).Struct.fields;
+    inline for (fields, 0..) |field, i| {
+        self.atoms_extra.items[index + i] = switch (field.type) {
+            u32 => @field(extra, field.name),
+            else => @compileError("bad field type"),
+        };
+    }
+}
+
+pub fn getEntryRef(self: InternalObject, macho_file: *MachO) ?MachO.Ref {
+    const index = self.entry_index orelse return null;
+    return self.getSymbolRef(index, macho_file);
+}
+
+pub fn getDyldStubBinderRef(self: InternalObject, macho_file: *MachO) ?MachO.Ref {
+    const index = self.dyld_stub_binder_index orelse return null;
+    return self.getSymbolRef(index, macho_file);
+}
+
+pub fn getDyldPrivateRef(self: InternalObject, macho_file: *MachO) ?MachO.Ref {
+    const index = self.dyld_private_index orelse return null;
+    return self.getSymbolRef(index, macho_file);
+}
+
+pub fn getObjcMsgSendRef(self: InternalObject, macho_file: *MachO) ?MachO.Ref {
+    const index = self.objc_msg_send_index orelse return null;
+    return self.getSymbolRef(index, macho_file);
+}
+
+pub fn addSymbol(self: *InternalObject, allocator: Allocator) !Symbol.Index {
+    try self.symbols.ensureUnusedCapacity(allocator, 1);
+    return self.addSymbolAssumeCapacity();
+}
+
+pub fn addSymbolAssumeCapacity(self: *InternalObject) Symbol.Index {
+    const index: Symbol.Index = @intCast(self.symbols.items.len);
+    const symbol = self.symbols.addOneAssumeCapacity();
+    symbol.* = .{ .file = self.index };
+    return index;
+}
+
+pub fn getSymbolRef(self: InternalObject, index: Symbol.Index, macho_file: *MachO) MachO.Ref {
+    const global_index = self.globals.items[index];
+    if (macho_file.resolver.get(global_index)) |ref| return ref;
+    return .{ .index = index, .file = self.index };
+}
+
+pub fn addSymbolExtra(self: *InternalObject, allocator: Allocator, extra: Symbol.Extra) !u32 {
+    const fields = @typeInfo(Symbol.Extra).Struct.fields;
+    try self.symbols_extra.ensureUnusedCapacity(allocator, fields.len);
+    return self.addSymbolExtraAssumeCapacity(extra);
+}
+
+fn addSymbolExtraAssumeCapacity(self: *InternalObject, extra: Symbol.Extra) u32 {
+    const index = @as(u32, @intCast(self.symbols_extra.items.len));
+    const fields = @typeInfo(Symbol.Extra).Struct.fields;
+    inline for (fields) |field| {
+        self.symbols_extra.appendAssumeCapacity(switch (field.type) {
+            u32 => @field(extra, field.name),
+            else => @compileError("bad field type"),
+        });
+    }
+    return index;
+}
+
+pub fn getSymbolExtra(self: InternalObject, index: u32) Symbol.Extra {
+    const fields = @typeInfo(Symbol.Extra).Struct.fields;
+    var i: usize = index;
+    var result: Symbol.Extra = undefined;
+    inline for (fields) |field| {
+        @field(result, field.name) = switch (field.type) {
+            u32 => self.symbols_extra.items[i],
+            else => @compileError("bad field type"),
+        };
+        i += 1;
+    }
+    return result;
+}
+
+pub fn setSymbolExtra(self: *InternalObject, index: u32, extra: Symbol.Extra) void {
+    const fields = @typeInfo(Symbol.Extra).Struct.fields;
+    inline for (fields, 0..) |field, i| {
+        self.symbols_extra.items[index + i] = switch (field.type) {
+            u32 => @field(extra, field.name),
+            else => @compileError("bad field type"),
+        };
+    }
+}
+
 const FormatContext = struct {
     self: *InternalObject,
     macho_file: *MachO,
@@ -309,8 +804,8 @@ fn formatAtoms(
     _ = unused_fmt_string;
     _ = options;
     try writer.writeAll("  atoms\n");
-    for (ctx.self.atoms.items) |atom_index| {
-        const atom = ctx.macho_file.getAtom(atom_index).?;
+    for (ctx.self.getAtoms()) |atom_index| {
+        const atom = ctx.self.getAtom(atom_index) orelse continue;
         try writer.print("    {}\n", .{atom.fmt(ctx.macho_file)});
     }
 }
@@ -330,10 +825,17 @@ fn formatSymtab(
 ) !void {
     _ = unused_fmt_string;
     _ = options;
+    const macho_file = ctx.macho_file;
+    const self = ctx.self;
     try writer.writeAll("  symbols\n");
-    for (ctx.self.symbols.items) |index| {
-        const global = ctx.macho_file.getSymbol(index);
-        try writer.print("    {}\n", .{global.fmt(ctx.macho_file)});
+    for (self.symbols.items, 0..) |sym, i| {
+        const ref = self.getSymbolRef(@intCast(i), macho_file);
+        if (ref.getFile(macho_file) == null) {
+            // TODO any better way of handling this?
+            try writer.print("    {s} : unclaimed\n", .{sym.getName(macho_file)});
+        } else {
+            try writer.print("    {}\n", .{ref.getSymbol(macho_file).?.fmt(macho_file)});
+        }
     }
 }
 
@@ -352,6 +854,7 @@ const assert = std.debug.assert;
 const macho = std.macho;
 const mem = std.mem;
 const std = @import("std");
+const trace = @import("../../tracy.zig").trace;
 
 const Allocator = std.mem.Allocator;
 const Atom = @import("Atom.zig");