macho: use MappedFile to parse input Dylibs

Author: kubkon

src/link/MachO.zig

@@ -1456,14 +1456,6 @@ fn parseArchive(self: *MachO, path: []const u8, force_load: bool) !bool {
     return true;
 }
 
-const ParseDylibError = error{
-    OutOfMemory,
-    EmptyStubFile,
-    MismatchedCpuArchitecture,
-    UnsupportedCpuArchitecture,
-    EndOfStream,
-} || fs.File.OpenError || std.os.PReadError || Dylib.Id.ParseError;
-
 const DylibCreateOpts = struct {
     syslibroot: ?[]const u8,
     id: ?Dylib.Id = null,
@@ -1472,12 +1464,12 @@ const DylibCreateOpts = struct {
     weak: bool = false,
 };
 
-pub fn parseDylib(
+fn parseDylib(
     self: *MachO,
     path: []const u8,
     dependent_libs: anytype,
     opts: DylibCreateOpts,
-) ParseDylibError!bool {
+) !bool {
     const gpa = self.base.allocator;
     const file = fs.cwd().openFile(path, .{}) catch |err| switch (err) {
         error.FileNotFound => return false,
@@ -1491,11 +1483,10 @@ pub fn parseDylib(
     const reader = file.reader();
     const fat_offset = math.cast(usize, try fat.getLibraryOffset(reader, cpu_arch)) orelse
         return error.Overflow;
-    try file.seekTo(fat_offset);
     file_size -= fat_offset;
 
-    const data = try file.readToEndAlloc(gpa, file_size);
-    defer gpa.free(data);
+    const data = try MappedFile.mapWithOptions(gpa, file, file_size, fat_offset);
+    defer data.unmap(gpa);
 
     const dylib_id = @intCast(u16, self.dylibs.items.len);
     var dylib = Dylib{ .weak = opts.weak };

src/link/MachO/Dylib.zig

@@ -15,6 +15,7 @@ const CrossTarget = std.zig.CrossTarget;
 const LibStub = @import("../tapi.zig").LibStub;
 const LoadCommandIterator = macho.LoadCommandIterator;
 const MachO = @import("../MachO.zig");
+const MappedFile = @import("../MappedFile.zig");
 
 id: ?Id = null,
 weak: bool = false,
@@ -124,9 +125,10 @@ pub fn parseFromBinary(
     dylib_id: u16,
     dependent_libs: anytype,
     name: []const u8,
-    data: []const u8,
+    data: MappedFile,
 ) !void {
-    var stream = std.io.fixedBufferStream(data);
+    const slice = data.slice();
+    var stream = std.io.fixedBufferStream(slice);
     const reader = stream.reader();
 
     log.debug("parsing shared library '{s}'", .{name});
@@ -151,17 +153,18 @@ pub fn parseFromBinary(
     const should_lookup_reexports = header.flags & macho.MH_NO_REEXPORTED_DYLIBS == 0;
     var it = LoadCommandIterator{
         .ncmds = header.ncmds,
-        .buffer = data[@sizeOf(macho.mach_header_64)..][0..header.sizeofcmds],
+        .buffer = slice[@sizeOf(macho.mach_header_64)..][0..header.sizeofcmds],
     };
     while (it.next()) |cmd| {
         switch (cmd.cmd()) {
             .SYMTAB => {
                 const symtab_cmd = cmd.cast(macho.symtab_command).?;
+                // SYMTAB in a final binary file (exe or lib) has to be aligned in file
                 const symtab = @ptrCast(
                     [*]const macho.nlist_64,
-                    @alignCast(@alignOf(macho.nlist_64), &data[symtab_cmd.symoff]),
+                    @alignCast(@alignOf(macho.nlist_64), slice.ptr + symtab_cmd.symoff),
                 )[0..symtab_cmd.nsyms];
-                const strtab = data[symtab_cmd.stroff..][0..symtab_cmd.strsize];
+                const strtab = slice[symtab_cmd.stroff..][0..symtab_cmd.strsize];
 
                 for (symtab) |sym| {
                     const add_to_symtab = sym.ext() and (sym.sect() or sym.indr());