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link.MachO: use accurate alignment attribute on pointers

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Also adds a new method to ArrayList: appendUnalignedSlice
This commit is contained in:
Andrew Kelley 2022-08-10 22:26:29 -07:00
parent cc56400e62
commit fa620ef710
4 changed files with 80 additions and 16 deletions
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63
lib/std/array_list.zig
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@ -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);

6
src/link/MachO.zig
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@ -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");

2
src/link/MachO/Atom.zig
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@ -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();

25
src/link/MachO/Object.zig
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@ -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) = .{},
@ -99,12 +99,13 @@ 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 = @ptrCast(
[*]const macho.nlist_64,
@alignCast(@alignOf(macho.nlist_64), &self.contents[symtab.symoff]),
[*]align(1) const macho.nlist_64,
self.contents.ptr + symtab.symoff,
)[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 => {},
}
@ -196,10 +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,
@ -303,8 +304,8 @@ pub fn splitIntoAtomsOneShot(self: *Object, macho_file: *MachO, object_id: u32)
// Read section's list of relocations
const relocs = @ptrCast(
[*]const macho.relocation_info,
@alignCast(@alignOf(macho.relocation_info), &self.contents[sect.reloff]),
[*]align(1) const macho.relocation_info,
self.contents.ptr + sect.reloff,
)[0..sect.nreloc];
// Symbols within this section only.
@ -472,7 +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,
@ -538,7 +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],
@ -549,8 +550,8 @@ pub fn parseDataInCode(self: Object) ?[]const macho.data_in_code_entry {
const dice = cmd.cast(macho.linkedit_data_command).?;
const ndice = @divExact(dice.datasize, @sizeOf(macho.data_in_code_entry));
return @ptrCast(
[*]const macho.data_in_code_entry,
@alignCast(@alignOf(macho.data_in_code_entry), &self.contents[dice.dataoff]),
[*]align(1) const macho.data_in_code_entry,
self.contents.ptr + dice.dataoff,
)[0..ndice];
},
else => {},