[lld-macho] Generate ObjC symbols from .tbd files

[int3]

Summary

I followed similar logic in TapiFile.cpp.

[compnerd]

lld/MachO/InputFiles.cpp

394

Does this really need the full context?

421

Same as last time - would be nice to actually compose with the user label prefix.

Remember that x86_64-apple-coff is a real target - and the user label prefix is empty there. This breaks because you are assuming that the user label prefix is _.

lld/test/MachO/Inputs/MacOSX.sdk/System/Library/Frameworks/CoreFoundation.framework/CoreFoundation.tbd

13

Id really rather see a second library added (Foundation.tbd) rather than put this into CoreFoundation. This makes it confusing for others IMO.

lld/test/MachO/stub-link.s

6

I think that we should go through and actually improve all the tests to use -syslibroot. This really looks far better (and matches the real world usage).

[int3]

lld/MachO/InputFiles.cpp

394

I don't think explicit captures add much to readability, especially for such a small lambda body...

(I don't think avoiding auto does either, that was @ruiu's preference)

421

Remember that x86_64-apple-coff is a real target

oh what... is this actually used?

lld/test/MachO/Inputs/MacOSX.sdk/System/Library/Frameworks/CoreFoundation.framework/CoreFoundation.tbd

13

these members are from CoreFoundation in the actual SDK, though...

lld/test/MachO/stub-link.s

6

agreed, will do it in a separate commit

[smeenai]

lld/MachO/InputFiles.cpp

410

Huh, interesting. I thought -ObjC only influenced the behavior for static libraries.

421

I believe it's used for UEFI. Presumably that's something for LLD for COFF to worry about and not LLD for Mach-O though, right? Also, I'd be surprised if Objective-C is being used for UEFI :)

[compnerd]

lld/MachO/InputFiles.cpp

421

Sorry, that was a partial thought. What I was getting at is that the user label prefix is important and in that case, you have MachO conversions that occur. We should be more careful about the user label prefix rather than assume that it is guaranteed to be _. That is a convention that is target dependent and not MachO dependent.

[smeenai]

lld/MachO/InputFiles.cpp

421

I agree with you in theory, but in practice, are there any targets we'll be linking with LLD for Mach-O where you wouldn't expect the underscore? I think we're pretty much assuming that Mach-O == an Apple Mach-O target; we're certainly not testing with anything else.

Out of curiosity, what does ld64 do?

[int3]

lld/MachO/InputFiles.cpp

421

ld64 includes the underscore prefixes in their string literals

[smeenai]

LGTM

lld/MachO/InputFiles.cpp

421

I think it's pretty justifiable to use the underscore directly as well here then.

lld/test/MachO/Inputs/MacOSX.sdk/System/Library/Frameworks/CoreFoundation.framework/CoreFoundation.tbd

13

Huh, TIL.

lld/MachO/InputFiles.cpp

 
 DylibFile::DylibFile(std::shared_ptr<llvm::MachO::InterfaceFile> interface,
                      DylibFile *umbrella)
     : InputFile(DylibKind, MemoryBufferRef()) {
   if (umbrella == nullptr)
     umbrella = this;
 
   dylibName = saver.save(interface->getInstallName());
+  auto addSymbol = [&](const Twine &name) -> void {
+    symbols.push_back(symtab->addDylib(saver.save(name), umbrella,
+                                       /*isWeakDef=*/false,
+                                       /*isTlv=*/false));
+  };
   // TODO(compnerd) filter out symbols based on the target platform
   // TODO: handle weak defs, thread locals
-  for (const auto symbol : interface->symbols())
-    if (symbol->getArchitectures().has(config->arch))
-      symbols.push_back(symtab->addDylib(saver.save(symbol->getName()),
-                                         umbrella, /*isWeakDef=*/false,
-                                         /*isTlv=*/false));
+  for (const auto symbol : interface->symbols()) {
+    if (!symbol->getArchitectures().has(config->arch))
+      continue;
+
+    switch (symbol->getKind()) {
+    case SymbolKind::GlobalSymbol:
+      addSymbol(symbol->getName());
+      break;
+    case SymbolKind::ObjectiveCClass:
+      // XXX ld64 only creates these symbols when -ObjC is passed in. We may
+      // want to emulate that.
+      addSymbol("_OBJC_CLASS_$_" + symbol->getName());
+      addSymbol("_OBJC_METACLASS_$_" + symbol->getName());
+      break;
+    case SymbolKind::ObjectiveCClassEHType:
+      addSymbol("_OBJC_EHTYPE_$_" + symbol->getName());
+      break;
+    case SymbolKind::ObjectiveCInstanceVariable:
+      addSymbol("_OBJC_IVAR_$_" + symbol->getName());
+      break;
+    }
+  }
   // TODO(compnerd) properly represent the hierarchy of the documents as it is
   // in theory possible to have re-exported dylibs from re-exported dylibs which
   // should be parent'ed to the child.
   for (auto document : interface->documents())
     reexported.push_back(make<DylibFile>(document, umbrella));
 }
 
 ArchiveFile::ArchiveFile(std::unique_ptr<llvm::object::Archive> &&f)

lld/test/MachO/Inputs/MacOSX.sdk/System/Library/Frameworks/CoreFoundation.framework/CoreFoundation.tbd

 --- !tapi-tbd-v3
 archs:            [ x86_64 ]
 uuids:            [ 'x86_64: 00000000-0000-0000-0000-000000000000' ]
 platform:         macosx
 install-name:     '/System/Library/Frameworks/CoreFoundation.framework/CoreFoundation'
 current-version:  0001.001.1
 compatibility-version: 150
 exports:
-  - archs:        [ 'x86_64' ]
-    symbols:      [ '__CFBigNumGetInt128' ]
+  - archs:         [ 'x86_64' ]
+    symbols:       [ '__CFBigNumGetInt128' ]
+    objc-classes:  [ NSObject ]
+    objc-ivars:    [ NSConstantArray._count ]
+    objc-eh-types: [ NSException ]

lld/test/MachO/stub-link.s

 # REQUIRES: x86
 
 # RUN: mkdir -p %t
 #
 # RUN: llvm-mc -filetype obj -triple x86_64-apple-darwin %s -o %t/test.o
-# RUN: lld -flavor darwinnew -o %t/test -Z -L%S/Inputs/MacOSX.sdk/usr/lib -lSystem %t/test.o
+# RUN: lld -flavor darwinnew -o %t/test -syslibroot %S/Inputs/MacOSX.sdk -lSystem -framework CoreFoundation %t/test.o
 #
 # RUN: llvm-objdump --bind --no-show-raw-insn -d -r %t/test | FileCheck %s
 
 # CHECK: Disassembly of section __TEXT,__text:
 # CHECK: movq {{.*}} # [[ADDR:[0-9a-f]+]]
 
 # CHECK: Bind table:
-# CHECK: __DATA_CONST __got 0x[[ADDR]] pointer 0 libSystem ___nan
+# CHECK-DAG: __DATA_CONST __got 0x[[ADDR]] pointer 0 libSystem ___nan
+# CHECK-DAG: __DATA __data {{.*}} pointer 0 CoreFoundation _OBJC_CLASS_$_NSObject
+# CHECK-DAG: __DATA __data {{.*}} pointer 0 CoreFoundation _OBJC_METACLASS_$_NSObject
+# CHECK-DAG: __DATA __data {{.*}} pointer 0 CoreFoundation _OBJC_IVAR_$_NSConstantArray._count
+# CHECK-DAG: __DATA __data {{.*}} pointer 0 CoreFoundation _OBJC_EHTYPE_$_NSException
 
 .section __TEXT,__text
 .global _main
 
 _main:
   movq ___nan@GOTPCREL(%rip), %rax
   ret
+
+.data
+  .quad _OBJC_CLASS_$_NSObject
+  .quad _OBJC_METACLASS_$_NSObject
+  .quad _OBJC_IVAR_$_NSConstantArray._count
+  .quad _OBJC_EHTYPE_$_NSException