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macho: handle and test tentative definitions
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@kubkon
kubkon committed Nov 23, 2023
1 parent e5e74c4 commit c5570b5
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Showing 6 changed files with 102 additions and 13 deletions.
8 changes: 7 additions & 1 deletion src/MachO.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -256,8 +256,8 @@ pub fn flush(self: *MachO) !void {
}

// TODO kill __eh_frame atoms
// TODO convert tentative definitions

try self.convertTentativeDefinitions();
self.markImportsAndExports();

// TODO dead strip atoms
Expand Down Expand Up @@ -938,6 +938,12 @@ fn markLive(self: *MachO) void {
}
}

fn convertTentativeDefinitions(self: *MachO) !void {
for (self.objects.items) |index| {
try self.getFile(index).?.object.convertTentativeDefinitions(self);
}
}

fn markImportsAndExports(self: *MachO) void {
if (!self.options.dylib)
for (self.dylibs.items) |index| {
Expand Down
2 changes: 1 addition & 1 deletion src/MachO/Atom.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -45,7 +45,7 @@ pub fn getFile(self: Atom, macho_file: *MachO) File {
pub fn getInputSection(self: Atom, macho_file: *MachO) macho.section_64 {
return switch (self.getFile(macho_file)) {
.internal => |x| x.sections.items[self.n_sect],
.object => |x| x.sections[self.n_sect],
.object => |x| x.sections.items[self.n_sect],
else => unreachable,
};
}
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4 changes: 2 additions & 2 deletions src/MachO/Dylib.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -356,7 +356,7 @@ pub fn resolveSymbols(self: *Dylib, macho_file: *MachO) void {
const nlist_idx = @as(Symbol.Index, @intCast(i));
const nlist = self.symtab.items[nlist_idx];

if (nlist.undf()) continue;
if (nlist.undf() and !nlist.tentative()) continue;

const global = macho_file.getSymbol(index);
if (self.asFile().getSymbolRank(nlist, false) < global.getSymbolRank(macho_file)) {
Expand All @@ -372,7 +372,7 @@ pub fn resolveSymbols(self: *Dylib, macho_file: *MachO) void {
pub fn markLive(self: *Dylib, macho_file: *MachO) void {
for (self.symbols.items, 0..) |index, i| {
const nlist = self.symtab.items[i];
if (!nlist.undf()) continue;
if (!nlist.undf() or nlist.tentative()) continue;

const global = macho_file.getSymbol(index);
const file = global.getFile(macho_file) orelse continue;
Expand Down
2 changes: 1 addition & 1 deletion src/MachO/InternalObject.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -116,7 +116,7 @@ pub fn resolveSymbols(self: *InternalObject, macho_file: *MachO) void {
const nlist_idx = @as(Symbol.Index, @intCast(i));
const nlist = self.symtab.items[nlist_idx];

if (nlist.undf()) continue;
if (nlist.undf() and !nlist.tentative()) continue;

const global = macho_file.getSymbol(index);
if (self.asFile().getSymbolRank(nlist, false) < global.getSymbolRank(macho_file)) {
Expand Down
71 changes: 63 additions & 8 deletions src/MachO/Object.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,7 @@ data: []const u8,
index: File.Index,

header: ?macho.mach_header_64 = null,
sections: []align(1) const macho.section_64 = &[0]macho.section_64{},
sections: std.ArrayListUnmanaged(macho.section_64) = .{},
symtab: std.ArrayListUnmanaged(macho.nlist_64) = .{},
strtab: []const u8 = &[0]u8{},
first_global: Symbol.Index = 0,
Expand Down Expand Up @@ -45,7 +45,9 @@ pub fn parse(self: *Object, macho_file: *MachO) !void {
self.header = try reader.readStruct(macho.mach_header_64);

const lc_seg = self.getLoadCommand(.SEGMENT_64) orelse return;
self.sections = lc_seg.getSections();
const sections = lc_seg.getSections();
try self.sections.ensureUnusedCapacity(gpa, sections.len);
self.sections.appendUnalignedSliceAssumeCapacity(sections);

const lc_symtab = self.getLoadCommand(.SYMTAB) orelse return;
const cmd = lc_symtab.cast(macho.symtab_command).?;
Expand All @@ -71,14 +73,14 @@ pub fn parse(self: *Object, macho_file: *MachO) !void {

fn initSectionAtoms(self: *Object, macho_file: *MachO) !void {
const gpa = macho_file.base.allocator;
try self.atoms.resize(gpa, self.sections.len);
try self.atoms.resize(gpa, self.sections.items.len);
@memset(self.atoms.items, 0);

for (self.sections, 0..) |sect, n_sect| {
for (self.sections.items, 0..) |sect, n_sect| {
if (sect.attrs() & macho.S_ATTR_DEBUG != 0) continue;
if (sect.type() == macho.S_COALESCED and mem.eql(u8, "__eh_frame", sect.sectName())) continue;

const name = try std.fmt.allocPrintZ(gpa, "{s},{s}", .{ sect.segName(), sect.sectName() });
const name = try std.fmt.allocPrintZ(gpa, "{s}${s}", .{ sect.segName(), sect.sectName() });
defer gpa.free(name);
const atom_index = try self.addAtom(name, sect.size, sect.@"align", @intCast(n_sect), macho_file);
const atom = macho_file.getAtom(atom_index).?;
Expand Down Expand Up @@ -128,7 +130,7 @@ fn initSymbols(self: *Object, macho_file: *MachO) !void {
const symbol = macho_file.getSymbol(index);
const name = self.getString(local.n_strx);
symbol.* = .{
.value = local.n_value - self.sections[local.n_sect - 1].addr,
.value = local.n_value - self.sections.items[local.n_sect - 1].addr,
.name = try macho_file.string_intern.insert(gpa, name),
.nlist_idx = @intCast(i),
.atom = if (local.abs()) 0 else self.atoms.items[local.n_sect - 1],
Expand Down Expand Up @@ -295,7 +297,7 @@ pub fn resolveSymbols(self: *Object, macho_file: *MachO) void {
const nlist_idx = @as(Symbol.Index, @intCast(self.first_global + i));
const nlist = self.symtab.items[nlist_idx];

if (nlist.undf()) continue;
if (nlist.undf() and !nlist.tentative()) continue;
if (!nlist.tentative() and !nlist.abs()) {
const atom_index = self.atoms.items[nlist.n_sect - 1];
const atom = macho_file.getAtom(atom_index) orelse continue;
Expand All @@ -308,7 +310,7 @@ pub fn resolveSymbols(self: *Object, macho_file: *MachO) void {
var value = nlist.n_value;
if (!nlist.tentative() and !nlist.abs()) {
atom = self.atoms.items[nlist.n_sect - 1];
value -= self.sections[nlist.n_sect - 1].addr;
value -= self.sections.items[nlist.n_sect - 1].addr;
}
global.value = value;
global.atom = atom;
Expand Down Expand Up @@ -347,6 +349,59 @@ pub fn scanRelocs(self: Object, macho_file: *MachO) !void {
// TODO scan __eh_frame relocs
}

pub fn convertTentativeDefinitions(self: *Object, macho_file: *MachO) !void {
const gpa = macho_file.base.allocator;
for (self.getGlobals(), 0..) |index, i| {
const nlist_idx = @as(Symbol.Index, @intCast(self.first_global + i));
const nlist = &self.symtab.items[nlist_idx];
if (!nlist.tentative()) continue;

const global = macho_file.getSymbol(index);
const global_file = global.getFile(macho_file).?;
if (global_file.getIndex() != self.index) {
// if (elf_file.options.warn_common) {
// elf_file.base.warn("{}: multiple common symbols: {s}", .{
// self.fmtPath(),
// global.getName(elf_file),
// });
// }
continue;
}

const atom_index = try macho_file.addAtom();
try self.atoms.append(gpa, atom_index);

const name = try std.fmt.allocPrintZ(gpa, "__DATA$__common${s}", .{global.getName(macho_file)});
defer gpa.free(name);
const atom = macho_file.getAtom(atom_index).?;
atom.atom_index = atom_index;
atom.name = try macho_file.string_intern.insert(gpa, name);
atom.file = self.index;
atom.size = nlist.n_value;
atom.alignment = (nlist.n_desc >> 8) & 0x0f;

const n_sect = @as(u8, @intCast(self.sections.items.len));
const sect = try self.sections.addOne(gpa);
sect.* = .{
.sectname = MachO.makeStaticString("__common"),
.segname = MachO.makeStaticString("__DATA"),
.flags = macho.S_ZEROFILL,
.size = atom.size,
.@"align" = atom.alignment,
};
atom.n_sect = n_sect;

global.value = 0;
global.atom = atom_index;
global.flags.weak = false;

nlist.n_value = 0;
nlist.n_type = macho.N_EXT | macho.N_SECT;
nlist.n_sect = n_sect + 1;
nlist.n_desc = 0;
}
}

pub fn calcSymtabSize(self: *Object, macho_file: *MachO) !void {
for (self.getLocals()) |local_index| {
const local = macho_file.getSymbol(local_index);
Expand Down
28 changes: 28 additions & 0 deletions test/macho.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -41,6 +41,7 @@ pub fn addMachOTests(b: *Build, options: common.Options) *Step {
macho_step.dependOn(testSearchStrategy(b, opts));
macho_step.dependOn(testStackSize(b, opts));
macho_step.dependOn(testTbdv3(b, opts));
macho_step.dependOn(testTentative(b, opts));
macho_step.dependOn(testTls(b, opts));
macho_step.dependOn(testUnwindInfo(b, opts));
macho_step.dependOn(testUnwindInfoNoSubsectionsArm64(b, opts));
Expand Down Expand Up @@ -959,6 +960,33 @@ fn testTbdv3(b: *Build, opts: Options) *Step {
return test_step;
}

fn testTentative(b: *Build, opts: Options) *Step {
const test_step = b.step("test-macho-tentative", "");

const exe = cc(b, opts);
exe.addCSource(
\\int foo;
\\int bar;
\\int baz = 42;
);
exe.addCSource(
\\#include<stdio.h>
\\int foo;
\\int bar = 5;
\\int baz;
\\int main() {
\\ printf("%d %d %d\n", foo, bar, baz);
\\}
);
exe.addArg("-fcommon");

const run = exe.run();
run.expectStdOutEqual("0 5 42\n");
test_step.dependOn(run.step());

return test_step;
}

fn testTls(b: *Build, opts: Options) *Step {
const test_step = b.step("test-macho-tls", "");

Expand Down

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