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pub fn gcAtoms(macho_file: *MachO) !void {
const gpa = macho_file.base.comp.gpa;
var objects = try std.array_list.Managed(File.Index).initCapacity(gpa, macho_file.objects.items.len + 1);
defer objects.deinit();
for (macho_file.objects.items) |index| objects.appendAssumeCapacity(index);
if (macho_file.internal_object) |index| objects.appendAssumeCapacity(index);
var roots = std.array_list.Managed(*Atom).init(gpa);
defer roots.deinit();
try collectRoots(&roots, objects.items, macho_file);
mark(roots.items, objects.items, macho_file);
prune(objects.items, macho_file);
}
fn collectRoots(roots: *std.array_list.Managed(*Atom), objects: []const File.Index, macho_file: *MachO) !void {
for (objects) |index| {
const object = macho_file.getFile(index).?;
for (object.getSymbols(), 0..) |*sym, i| {
const ref = object.getSymbolRef(@intCast(i), macho_file);
const file = ref.getFile(macho_file) orelse continue;
if (file.getIndex() != index) continue;
if (sym.flags.no_dead_strip or (macho_file.base.isDynLib() and sym.visibility == .global))
try markSymbol(sym, roots, macho_file);
}
for (object.getAtoms()) |atom_index| {
const atom = object.getAtom(atom_index) orelse continue;
const isec = atom.getInputSection(macho_file);
switch (isec.type()) {
macho.S_MOD_INIT_FUNC_POINTERS,
macho.S_MOD_TERM_FUNC_POINTERS,
=> if (markAtom(atom)) try roots.append(atom),
else => if (isec.isDontDeadStrip() and markAtom(atom)) {
try roots.append(atom);
},
}
}
}
for (macho_file.objects.items) |index| {
const object = macho_file.getFile(index).?.object;
for (object.unwind_records_indexes.items) |cu_index| {
const cu = object.getUnwindRecord(cu_index);
if (!cu.alive) continue;
if (cu.getFde(macho_file)) |fde| {
if (fde.getCie(macho_file).getPersonality(macho_file)) |sym| try markSymbol(sym, roots, macho_file);
} else if (cu.getPersonality(macho_file)) |sym| try markSymbol(sym, roots, macho_file);
}
}
if (macho_file.getInternalObject()) |obj| {
for (obj.force_undefined.items) |sym_index| {
const ref = obj.getSymbolRef(sym_index, macho_file);
if (ref.getFile(macho_file) != null) {
const sym = ref.getSymbol(macho_file).?;
try markSymbol(sym, roots, macho_file);
}
}
for (&[_]?Symbol.Index{
obj.entry_index,
obj.dyld_stub_binder_index,
obj.objc_msg_send_index,
}) |index| {
if (index) |idx| {
const ref = obj.getSymbolRef(idx, macho_file);
if (ref.getFile(macho_file) != null) {
const sym = ref.getSymbol(macho_file).?;
try markSymbol(sym, roots, macho_file);
}
}
}
}
}
fn markSymbol(sym: *Symbol, roots: *std.array_list.Managed(*Atom), macho_file: *MachO) !void {
const atom = sym.getAtom(macho_file) orelse return;
if (markAtom(atom)) try roots.append(atom);
}
fn markAtom(atom: *Atom) bool {
const already_visited = atom.visited.swap(true, .seq_cst);
return atom.isAlive() and !already_visited;
}
fn mark(roots: []*Atom, objects: []const File.Index, macho_file: *MachO) void {
for (roots) |root| {
markLive(root, macho_file);
}
var loop: bool = true;
while (loop) {
loop = false;
for (objects) |index| {
const file = macho_file.getFile(index).?;
for (file.getAtoms()) |atom_index| {
const atom = file.getAtom(atom_index) orelse continue;
const isec = atom.getInputSection(macho_file);
if (isec.isDontDeadStripIfReferencesLive() and
!(mem.eql(u8, isec.sectName(), "__eh_frame") or
mem.eql(u8, isec.sectName(), "__compact_unwind") or
isec.attrs() & macho.S_ATTR_DEBUG != 0) and
!atom.isAlive() and refersLive(atom, macho_file))
{
markLive(atom, macho_file);
loop = true;
}
}
}
}
}
fn markLive(atom: *Atom, macho_file: *MachO) void {
assert(atom.visited.load(.seq_cst));
atom.setAlive(true);
track_live_log.debug("{f}marking live atom({d},{s})", .{
track_live_level,
atom.atom_index,
atom.getName(macho_file),
});
if (build_options.enable_logging)
track_live_level.incr();
for (atom.getRelocs(macho_file)) |rel| {
const target_atom = switch (rel.tag) {
.local => rel.getTargetAtom(atom.*, macho_file),
.@"extern" => blk: {
const ref = rel.getTargetSymbolRef(atom.*, macho_file);
break :blk if (ref.getSymbol(macho_file)) |sym| sym.getAtom(macho_file) else null;
},
};
if (target_atom) |ta| {
if (markAtom(ta)) markLive(ta, macho_file);
}
}
const file = atom.getFile(macho_file);
for (atom.getUnwindRecords(macho_file)) |cu_index| {
const cu = file.object.getUnwindRecord(cu_index);
const cu_atom = cu.getAtom(macho_file);
if (markAtom(cu_atom)) markLive(cu_atom, macho_file);
if (cu.getLsdaAtom(macho_file)) |lsda| {
if (markAtom(lsda)) markLive(lsda, macho_file);
}
if (cu.getFde(macho_file)) |fde| {
const fde_atom = fde.getAtom(macho_file);
if (markAtom(fde_atom)) markLive(fde_atom, macho_file);
if (fde.getLsdaAtom(macho_file)) |lsda| {
if (markAtom(lsda)) markLive(lsda, macho_file);
}
}
}
}
fn refersLive(atom: *Atom, macho_file: *MachO) bool {
for (atom.getRelocs(macho_file)) |rel| {
const target_atom = switch (rel.tag) {
.local => rel.getTargetAtom(atom.*, macho_file),
.@"extern" => blk: {
const ref = rel.getTargetSymbolRef(atom.*, macho_file);
break :blk if (ref.getSymbol(macho_file)) |sym| sym.getAtom(macho_file) else null;
},
};
if (target_atom) |ta| {
if (ta.isAlive()) return true;
}
}
return false;
}
fn prune(objects: []const File.Index, macho_file: *MachO) void {
for (objects) |index| {
const file = macho_file.getFile(index).?;
for (file.getAtoms()) |atom_index| {
const atom = file.getAtom(atom_index) orelse continue;
if (!atom.visited.load(.seq_cst)) {
if (atom.alive.cmpxchgStrong(true, false, .seq_cst, .seq_cst) == null) {
atom.markUnwindRecordsDead(macho_file);
}
}
}
}
}
const Level = struct {
value: usize = 0,
fn incr(self: *@This()) void {
self.value += 1;
}
pub fn format(self: *const @This(), w: *Writer) Writer.Error!void {
try w.splatByteAll(' ', self.value);
}
};
var track_live_level: Level = .{};
const assert = std.debug.assert;
const build_options = @import("build_options");
const log = std.log.scoped(.dead_strip);
const macho = std.macho;
const math = std.math;
const mem = std.mem;
const trace = @import("../../tracy.zig").trace;
const track_live_log = std.log.scoped(.dead_strip_track_live);
const std = @import("std");
const Writer = std.Io.Writer;
const Allocator = mem.Allocator;
const Atom = @import("Atom.zig");
const File = @import("file.zig").File;
const MachO = @import("../MachO.zig");
const Symbol = @import("Symbol.zig");
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