Merge pull request #12405 from ziglang/macho-aligned-ptrs

link.MachO: use accurate alignment attribute on pointers

Author: andrewrk

lib/std/array_list.zig

@@ -221,6 +221,30 @@ pub fn ArrayListAligned(comptime T: type, comptime alignment: ?u29) type {
             mem.copy(T, self.items[old_len..], items);
         }
 
+        /// Append an unaligned slice of items to the list. Allocates more
+        /// memory as necessary. Only call this function if calling
+        /// `appendSlice` instead would be a compile error.
+        pub fn appendUnalignedSlice(self: *Self, items: []align(1) const T) Allocator.Error!void {
+            try self.ensureUnusedCapacity(items.len);
+            self.appendUnalignedSliceAssumeCapacity(items);
+        }
+
+        /// Append the slice of items to the list, asserting the capacity is already
+        /// enough to store the new items. **Does not** invalidate pointers.
+        /// Only call this function if calling `appendSliceAssumeCapacity` instead
+        /// would be a compile error.
+        pub fn appendUnalignedSliceAssumeCapacity(self: *Self, items: []align(1) const T) void {
+            const old_len = self.items.len;
+            const new_len = old_len + items.len;
+            assert(new_len <= self.capacity);
+            self.items.len = new_len;
+            @memcpy(
+                @ptrCast([*]align(@alignOf(T)) u8, self.items.ptr + old_len),
+                @ptrCast([*]const u8, items.ptr),
+                items.len * @sizeOf(T),
+            );
+        }
+
         pub const Writer = if (T != u8)
             @compileError("The Writer interface is only defined for ArrayList(u8) " ++
                 "but the given type is ArrayList(" ++ @typeName(T) ++ ")")
@@ -592,6 +616,29 @@ pub fn ArrayListAlignedUnmanaged(comptime T: type, comptime alignment: ?u29) typ
             mem.copy(T, self.items[old_len..], items);
         }
 
+        /// Append the slice of items to the list. Allocates more
+        /// memory as necessary. Only call this function if a call to `appendSlice` instead would
+        /// be a compile error.
+        pub fn appendUnalignedSlice(self: *Self, allocator: Allocator, items: []align(1) const T) Allocator.Error!void {
+            try self.ensureUnusedCapacity(allocator, items.len);
+            self.appendUnalignedSliceAssumeCapacity(items);
+        }
+
+        /// Append an unaligned slice of items to the list, asserting the capacity is enough
+        /// to store the new items. Only call this function if a call to `appendSliceAssumeCapacity`
+        /// instead would be a compile error.
+        pub fn appendUnalignedSliceAssumeCapacity(self: *Self, items: []align(1) const T) void {
+            const old_len = self.items.len;
+            const new_len = old_len + items.len;
+            assert(new_len <= self.capacity);
+            self.items.len = new_len;
+            @memcpy(
+                @ptrCast([*]align(@alignOf(T)) u8, self.items.ptr + old_len),
+                @ptrCast([*]const u8, items.ptr),
+                items.len * @sizeOf(T),
+            );
+        }
+
         pub const WriterContext = struct {
             self: *Self,
             allocator: Allocator,
@@ -899,6 +946,14 @@ test "std.ArrayList/ArrayListUnmanaged.basic" {
         try testing.expect(list.pop() == 1);
         try testing.expect(list.items.len == 9);
 
+        var unaligned: [3]i32 align(1) = [_]i32{ 4, 5, 6 };
+        list.appendUnalignedSlice(&unaligned) catch unreachable;
+        try testing.expect(list.items.len == 12);
+        try testing.expect(list.pop() == 6);
+        try testing.expect(list.pop() == 5);
+        try testing.expect(list.pop() == 4);
+        try testing.expect(list.items.len == 9);
+
         list.appendSlice(&[_]i32{}) catch unreachable;
         try testing.expect(list.items.len == 9);
 
@@ -941,6 +996,14 @@ test "std.ArrayList/ArrayListUnmanaged.basic" {
         try testing.expect(list.pop() == 1);
         try testing.expect(list.items.len == 9);
 
+        var unaligned: [3]i32 align(1) = [_]i32{ 4, 5, 6 };
+        list.appendUnalignedSlice(a, &unaligned) catch unreachable;
+        try testing.expect(list.items.len == 12);
+        try testing.expect(list.pop() == 6);
+        try testing.expect(list.pop() == 5);
+        try testing.expect(list.pop() == 4);
+        try testing.expect(list.items.len == 9);
+
         list.appendSlice(a, &[_]i32{}) catch unreachable;
         try testing.expect(list.items.len == 9);
 

src/link/MachO.zig

@@ -5315,10 +5315,10 @@ fn writeFunctionStarts(self: *MachO, ncmds: *u32, lc_writer: anytype) !void {
 }
 
 fn filterDataInCode(
-    dices: []const macho.data_in_code_entry,
+    dices: []align(1) const macho.data_in_code_entry,
     start_addr: u64,
     end_addr: u64,
-) []const macho.data_in_code_entry {
+) []align(1) const macho.data_in_code_entry {
     const Predicate = struct {
         addr: u64,
 
@@ -5825,7 +5825,7 @@ pub fn getEntryPoint(self: MachO) error{MissingMainEntrypoint}!SymbolWithLoc {
     return global;
 }
 
-pub fn findFirst(comptime T: type, haystack: []const T, start: usize, predicate: anytype) usize {
+pub fn findFirst(comptime T: type, haystack: []align(1) const T, start: usize, predicate: anytype) usize {
     if (!@hasDecl(@TypeOf(predicate), "predicate"))
         @compileError("Predicate is required to define fn predicate(@This(), T) bool");
 

src/link/MachO/Atom.zig

@@ -218,7 +218,7 @@ const RelocContext = struct {
     base_offset: i32 = 0,
 };
 
-pub fn parseRelocs(self: *Atom, relocs: []const macho.relocation_info, context: RelocContext) !void {
+pub fn parseRelocs(self: *Atom, relocs: []align(1) const macho.relocation_info, context: RelocContext) !void {
     const tracy = trace(@src());
     defer tracy.end();
 

src/link/MachO/Object.zig

@@ -24,7 +24,7 @@ mtime: u64,
 contents: []align(@alignOf(u64)) const u8,
 
 header: macho.mach_header_64 = undefined,
-in_symtab: []const macho.nlist_64 = undefined,
+in_symtab: []align(1) const macho.nlist_64 = undefined,
 in_strtab: []const u8 = undefined,
 
 symtab: std.ArrayListUnmanaged(macho.nlist_64) = .{},
@@ -100,12 +100,12 @@ pub fn parse(self: *Object, allocator: Allocator, cpu_arch: std.Target.Cpu.Arch)
             .SYMTAB => {
                 const symtab = cmd.cast(macho.symtab_command).?;
                 // Sadly, SYMTAB may be at an unaligned offset within the object file.
-                self.in_symtab = @alignCast(@alignOf(macho.nlist_64), @ptrCast(
+                self.in_symtab = @ptrCast(
                     [*]align(1) const macho.nlist_64,
                     self.contents.ptr + symtab.symoff,
-                ))[0..symtab.nsyms];
+                )[0..symtab.nsyms];
                 self.in_strtab = self.contents[symtab.stroff..][0..symtab.strsize];
-                try self.symtab.appendSlice(allocator, self.in_symtab);
+                try self.symtab.appendUnalignedSlice(allocator, self.in_symtab);
             },
             else => {},
         }
@@ -197,10 +197,10 @@ fn filterSymbolsByAddress(
 }
 
 fn filterRelocs(
-    relocs: []const macho.relocation_info,
+    relocs: []align(1) const macho.relocation_info,
     start_addr: u64,
     end_addr: u64,
-) []const macho.relocation_info {
+) []align(1) const macho.relocation_info {
     const Predicate = struct {
         addr: u64,
 
@@ -303,10 +303,10 @@ pub fn splitIntoAtomsOneShot(self: *Object, macho_file: *MachO, object_id: u32)
         const code: ?[]const u8 = if (!sect.isZerofill()) try self.getSectionContents(sect) else null;
 
         // Read section's list of relocations
-        const relocs = @alignCast(@alignOf(macho.relocation_info), @ptrCast(
+        const relocs = @ptrCast(
             [*]align(1) const macho.relocation_info,
             self.contents.ptr + sect.reloff,
-        ))[0..sect.nreloc];
+        )[0..sect.nreloc];
 
         // Symbols within this section only.
         const filtered_syms = filterSymbolsByAddress(
@@ -473,7 +473,7 @@ fn createAtomFromSubsection(
     size: u64,
     alignment: u32,
     code: ?[]const u8,
-    relocs: []const macho.relocation_info,
+    relocs: []align(1) const macho.relocation_info,
     indexes: []const SymbolAtIndex,
     match: u8,
     sect: macho.section_64,
@@ -539,7 +539,7 @@ pub fn getSourceSection(self: Object, index: u16) macho.section_64 {
     return self.sections.items[index];
 }
 
-pub fn parseDataInCode(self: Object) ?[]const macho.data_in_code_entry {
+pub fn parseDataInCode(self: Object) ?[]align(1) const macho.data_in_code_entry {
     var it = LoadCommandIterator{
         .ncmds = self.header.ncmds,
         .buffer = self.contents[@sizeOf(macho.mach_header_64)..][0..self.header.sizeofcmds],
@@ -549,10 +549,10 @@ pub fn parseDataInCode(self: Object) ?[]const macho.data_in_code_entry {
             .DATA_IN_CODE => {
                 const dice = cmd.cast(macho.linkedit_data_command).?;
                 const ndice = @divExact(dice.datasize, @sizeOf(macho.data_in_code_entry));
-                return @alignCast(@alignOf(macho.data_in_code_entry), @ptrCast(
+                return @ptrCast(
                     [*]align(1) const macho.data_in_code_entry,
                     self.contents.ptr + dice.dataoff,
-                ))[0..ndice];
+                )[0..ndice];
             },
             else => {},
         }