From 6b617afe2a3904ad3d5c9e3542a30bd7f35ed54e Mon Sep 17 00:00:00 2001
From: Jakub Konka <kubkon@jakubkonka.com>
Date: Thu, 11 Jan 2024 18:50:53 +0100
Subject: [PATCH] macho: resolve synthetic symbols

---
 src/link/MachO.zig                | 48 +++++++++++++++++++++++++++++++
 src/link/MachO/InternalObject.zig | 12 ++++----
 2 files changed, 54 insertions(+), 6 deletions(-)

diff --git a/src/link/MachO.zig b/src/link/MachO.zig
index 8a43526fab..9514d6d71f 100644
--- a/src/link/MachO.zig
+++ b/src/link/MachO.zig
@@ -498,6 +498,7 @@ pub fn flushModule(self: *MachO, arena: Allocator, prog_node: *std.Progress.Node
 
     try self.addUndefinedGlobals();
     try self.resolveSymbols();
+    try self.resolveSyntheticSymbols();
 
     state_log.debug("{}", .{self.dumpState()});
 
@@ -1215,6 +1216,53 @@ fn markLive(self: *MachO) void {
     }
 }
 
+fn resolveSyntheticSymbols(self: *MachO) !void {
+    const internal = self.getInternalObject() orelse return;
+
+    if (!self.base.isDynLib()) {
+        self.mh_execute_header_index = try internal.addSymbol("__mh_execute_header", self);
+        const sym = self.getSymbol(self.mh_execute_header_index.?);
+        sym.flags.@"export" = true;
+        sym.flags.dyn_ref = true;
+        sym.visibility = .global;
+    } else {
+        self.mh_dylib_header_index = try internal.addSymbol("__mh_dylib_header", self);
+    }
+
+    self.dso_handle_index = try internal.addSymbol("___dso_handle", self);
+    self.dyld_private_index = try internal.addSymbol("dyld_private", self);
+
+    {
+        const gpa = self.base.comp.gpa;
+        var boundary_symbols = std.AutoHashMap(Symbol.Index, void).init(gpa);
+        defer boundary_symbols.deinit();
+
+        for (self.objects.items) |index| {
+            const object = self.getFile(index).?.object;
+            for (object.symbols.items, 0..) |sym_index, i| {
+                const nlist = object.symtab.items(.nlist)[i];
+                const name = self.getSymbol(sym_index).getName(self);
+                if (!nlist.undf() or !nlist.ext()) continue;
+                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$stop$"))
+                {
+                    _ = try boundary_symbols.put(sym_index, {});
+                }
+            }
+        }
+
+        try self.boundary_symbols.ensureTotalCapacityPrecise(gpa, boundary_symbols.count());
+
+        var it = boundary_symbols.iterator();
+        while (it.next()) |entry| {
+            _ = try internal.addSymbol(self.getSymbol(entry.key_ptr.*).getName(self), self);
+            self.boundary_symbols.appendAssumeCapacity(entry.key_ptr.*);
+        }
+    }
+}
+
 fn shrinkAtom(self: *MachO, atom_index: Atom.Index, new_block_size: u64) void {
     _ = self;
     _ = atom_index;
diff --git a/src/link/MachO/InternalObject.zig b/src/link/MachO/InternalObject.zig
index e139e4efab..26ec86bb67 100644
--- a/src/link/MachO/InternalObject.zig
+++ b/src/link/MachO/InternalObject.zig
@@ -20,9 +20,9 @@ pub fn deinit(self: *InternalObject, allocator: Allocator) void {
 }
 
 pub fn addSymbol(self: *InternalObject, name: [:0]const u8, macho_file: *MachO) !Symbol.Index {
-    const gpa = macho_file.base.allocator;
+    const gpa = macho_file.base.comp.gpa;
     try self.symbols.ensureUnusedCapacity(gpa, 1);
-    const off = try macho_file.string_intern.insert(gpa, name);
+    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);
@@ -37,7 +37,7 @@ pub fn addObjcMsgsendSections(self: *InternalObject, sym_name: []const u8, macho
 }
 
 fn addObjcMethnameSection(self: *InternalObject, methname: []const u8, macho_file: *MachO) !Atom.Index {
-    const gpa = macho_file.base.allocator;
+    const gpa = macho_file.base.comp.gpa;
     const atom_index = try macho_file.addAtom();
     try self.atoms.append(gpa, atom_index);
 
@@ -45,7 +45,7 @@ fn addObjcMethnameSection(self: *InternalObject, methname: []const u8, macho_fil
     defer gpa.free(name);
     const atom = macho_file.getAtom(atom_index).?;
     atom.atom_index = atom_index;
-    atom.name = try macho_file.string_intern.insert(gpa, name);
+    atom.name = try macho_file.strings.insert(gpa, name);
     atom.file = self.index;
     atom.size = methname.len + 1;
     atom.alignment = 0;
@@ -71,7 +71,7 @@ fn addObjcSelrefsSection(
     methname_atom_index: Atom.Index,
     macho_file: *MachO,
 ) !Atom.Index {
-    const gpa = macho_file.base.allocator;
+    const gpa = macho_file.base.comp.gpa;
     const atom_index = try macho_file.addAtom();
     try self.atoms.append(gpa, atom_index);
 
@@ -79,7 +79,7 @@ fn addObjcSelrefsSection(
     defer gpa.free(name);
     const atom = macho_file.getAtom(atom_index).?;
     atom.atom_index = atom_index;
-    atom.name = try macho_file.string_intern.insert(gpa, name);
+    atom.name = try macho_file.strings.insert(gpa, name);
     atom.file = self.index;
     atom.size = @sizeOf(u64);
     atom.alignment = 3;