macho: emit local symbols for thunks

Author: kubkon

src/link/MachO.zig

@@ -1909,7 +1909,7 @@ fn calcSectionSizes(self: *MachO) !void {
             }
         }
 
-        // At this point, we can also calculate symtab and data-in-code linkedit section sizes
+        // At this point, we can also calculate most of the symtab and data-in-code linkedit section sizes
         if (self.getZigObject()) |zo| {
             tp.spawnWg(&wg, File.calcSymtabSize, .{ zo.asFile(), self });
         }
@@ -2463,6 +2463,9 @@ fn writeSectionsAndUpdateLinkeditSizes(self: *MachO) !void {
         if (self.getInternalObject()) |obj| {
             tp.spawnWg(&wg, File.writeSymtab, .{ obj.asFile(), self, self });
         }
+        if (self.requiresThunks()) for (self.thunks.items) |th| {
+            tp.spawnWg(&wg, Thunk.writeSymtab, .{ th, self, self });
+        };
     }
 
     if (self.has_errors.swap(false, .seq_cst)) return error.FlushFailure;
@@ -2725,6 +2728,14 @@ fn calcSymtabSize(self: *MachO) !void {
     var nimports: u32 = 0;
     var strsize: u32 = 1;
 
+    if (self.requiresThunks()) for (self.thunks.items) |*th| {
+        th.output_symtab_ctx.ilocal = nlocals;
+        th.output_symtab_ctx.stroff = strsize;
+        th.calcSymtabSize(self);
+        nlocals += th.output_symtab_ctx.nlocals;
+        strsize += th.output_symtab_ctx.strsize;
+    };
+
     for (files.items) |index| {
         const file = self.getFile(index).?;
         const ctx = switch (file) {

src/link/MachO/thunks.zig

@@ -85,6 +85,7 @@ pub const Thunk = struct {
     value: u64 = 0,
     out_n_sect: u8 = 0,
     symbols: std.AutoArrayHashMapUnmanaged(MachO.Ref, void) = .{},
+    output_symtab_ctx: MachO.SymtabCtx = .{},
 
     pub fn deinit(thunk: *Thunk, allocator: Allocator) void {
         thunk.symbols.deinit(allocator);
@@ -116,6 +117,34 @@ pub const Thunk = struct {
         }
     }
 
+    pub fn calcSymtabSize(thunk: *Thunk, macho_file: *MachO) void {
+        thunk.output_symtab_ctx.nlocals = @as(u32, @intCast(thunk.symbols.keys().len));
+        for (thunk.symbols.keys()) |ref| {
+            const sym = ref.getSymbol(macho_file).?;
+            thunk.output_symtab_ctx.strsize += @as(u32, @intCast(sym.getName(macho_file).len + "__thunk".len + 1));
+        }
+    }
+
+    pub fn writeSymtab(thunk: Thunk, macho_file: *MachO, ctx: anytype) void {
+        var n_strx = thunk.output_symtab_ctx.stroff;
+        for (thunk.symbols.keys(), thunk.output_symtab_ctx.ilocal..) |ref, ilocal| {
+            const sym = ref.getSymbol(macho_file).?;
+            const name = sym.getName(macho_file);
+            const out_sym = &ctx.symtab.items[ilocal];
+            out_sym.n_strx = n_strx;
+            @memcpy(ctx.strtab.items[n_strx..][0..name.len], name);
+            n_strx += @intCast(name.len);
+            @memcpy(ctx.strtab.items[n_strx..][0.."__thunk".len], "__thunk");
+            n_strx += @intCast("__thunk".len);
+            ctx.strtab.items[n_strx] = 0;
+            n_strx += 1;
+            out_sym.n_type = macho.N_SECT;
+            out_sym.n_sect = @intCast(thunk.out_n_sect + 1);
+            out_sym.n_value = @intCast(thunk.getTargetAddress(ref, macho_file));
+            out_sym.n_desc = 0;
+        }
+    }
+
     pub fn format(
         thunk: Thunk,
         comptime unused_fmt_string: []const u8,