macho: fix text block management

For the time being, until we rewrite how atoms are handled across
linkers, store two tables in the MachO linker: one for TextBlocks
directly created and managed by the linker, and one for TextBlocks
that were spawned by Module.Decl. This allows for correct memory
clean up after linking is done.

src/link/MachO.zig

@@ -188,9 +188,21 @@ text_block_free_list: std.ArrayListUnmanaged(*TextBlock) = .{},
 /// Pointer to the last allocated text block
 last_text_block: ?*TextBlock = null,
 
-managed_blocks: std.ArrayListUnmanaged(TextBlock) = .{},
+/// List of TextBlocks that are owned directly by the linker.
+/// Currently these are only TextBlocks that are the result of linking
+/// object files. TextBlock which take part in incremental linking are 
+/// at present owned by Module.Decl.
+/// TODO consolidate this.
+managed_blocks: std.ArrayListUnmanaged(*TextBlock) = .{},
+
 blocks: std.AutoHashMapUnmanaged(MatchingSection, *TextBlock) = .{},
 
+/// List of Decls that are currently alive.
+/// We store them here so that we can properly dispose of any allocated
+/// memory within the TextBlock in the incremental linker.
+/// TODO consolidate this.
+decls: std.ArrayListUnmanaged(*Module.Decl) = .{},
+
 /// A list of all PIE fixups required for this run of the linker.
 /// Warning, this is currently NOT thread-safe. See the TODO below.
 /// TODO Move this list inside `updateDecl` where it should be allocated
@@ -203,7 +215,7 @@ pie_fixups: std.ArrayListUnmanaged(PIEFixup) = .{},
 const StringIndexContext = struct {
     strtab: *std.ArrayListUnmanaged(u8),
 
-    pub fn eql(self: StringIndexContext, a: u32, b: u32) bool {
+    pub fn eql(_: StringIndexContext, a: u32, b: u32) bool {
         return a == b;
     }
 
@@ -2224,7 +2236,6 @@ fn resolveSymbols(self: *MachO) !void {
     for (self.tentatives.items) |sym| {
         if (symbolIsNull(sym)) continue;
 
-        const sym_name = self.getString(sym.n_strx);
         const match: MatchingSection = blk: {
             if (self.common_section_index == null) {
                 const data_seg = &self.load_commands.items[self.data_segment_cmd_index.?].Segment;
@@ -2263,12 +2274,13 @@ fn resolveSymbols(self: *MachO) !void {
             .local_sym_index = local_sym_index,
         };
 
-        const block = try self.managed_blocks.addOne(self.base.allocator);
+        const block = try self.base.allocator.create(TextBlock);
         block.* = TextBlock.empty;
         block.local_sym_index = local_sym_index;
         block.code = code;
         block.size = size;
         block.alignment = alignment;
+        try self.managed_blocks.append(self.base.allocator, block);
 
         // Update target section's metadata
         // TODO should we update segment's size here too?
@@ -2403,12 +2415,13 @@ fn resolveSymbols(self: *MachO) !void {
         // We create an empty atom for this symbol.
         // TODO perhaps we should special-case special symbols? Create a separate
         // linked list of atoms?
-        const block = try self.managed_blocks.addOne(self.base.allocator);
+        const block = try self.base.allocator.create(TextBlock);
         block.* = TextBlock.empty;
         block.local_sym_index = local_sym_index;
         block.code = try self.base.allocator.alloc(u8, 0);
         block.size = 0;
         block.alignment = 0;
+        try self.managed_blocks.append(self.base.allocator, block);
 
         if (self.blocks.getPtr(match)) |last| {
             last.*.next = block;
@@ -3306,12 +3319,18 @@ pub fn deinit(self: *MachO) void {
     }
     self.load_commands.deinit(self.base.allocator);
 
-    for (self.managed_blocks.items) |*block| {
+    for (self.managed_blocks.items) |block| {
         block.deinit(self.base.allocator);
+        self.base.allocator.destroy(block);
     }
     self.managed_blocks.deinit(self.base.allocator);
     self.blocks.deinit(self.base.allocator);
     self.text_block_free_list.deinit(self.base.allocator);
+
+    for (self.decls.items) |decl| {
+        decl.link.macho.deinit(self.base.allocator);
+    }
+    self.decls.deinit(self.base.allocator);
 }
 
 pub fn closeFiles(self: MachO) void {
@@ -3325,7 +3344,7 @@ pub fn closeFiles(self: MachO) void {
 
 fn freeTextBlock(self: *MachO, text_block: *TextBlock) void {
     log.debug("freeTextBlock {*}", .{text_block});
-    // text_block.deinit(self.base.allocator);
+    text_block.deinit(self.base.allocator);
 
     var already_have_free_list_node = false;
     {
@@ -3412,6 +3431,9 @@ pub fn allocateDeclIndexes(self: *MachO, decl: *Module.Decl) !void {
 
     try self.locals.ensureUnusedCapacity(self.base.allocator, 1);
     try self.got_entries.ensureUnusedCapacity(self.base.allocator, 1);
+    try self.decls.ensureUnusedCapacity(self.base.allocator, 1);
+
+    self.decls.appendAssumeCapacity(decl);
 
     if (self.locals_free_list.popOrNull()) |i| {
         log.debug("reusing symbol index {d} for {s}", .{ i, decl.name });
@@ -3497,7 +3519,6 @@ pub fn updateDecl(self: *MachO, module: *Module, decl: *Module.Decl) !void {
             .externally_managed => |x| break :blk x,
             .appended => {
                 decl.link.macho.code = code_buffer.toOwnedSlice();
-                log.warn("WAT", .{});
                 break :blk decl.link.macho.code;
             },
             .fail => |em| {

src/link/MachO/Object.zig

@@ -723,12 +723,13 @@ pub fn parseTextBlocks(self: *Object, macho_file: *MachO) !void {
                 break :blk block_local_sym_index;
             };
 
-            const block = try macho_file.managed_blocks.addOne(macho_file.base.allocator);
+            const block = try macho_file.base.allocator.create(TextBlock);
             block.* = TextBlock.empty;
             block.local_sym_index = block_local_sym_index;
             block.code = try self.allocator.dupe(u8, code);
             block.size = sect.size;
             block.alignment = sect.@"align";
+            try macho_file.managed_blocks.append(macho_file.base.allocator, block);
 
             try block.parseRelocsFromObject(self.allocator, relocs, self, .{
                 .base_addr = 0,