[lld-macho] Support -bundle

[int3]

Summary

Not 100% sure but it appears that bundles are almost identical to
dylibs, aside from the fact that they do not contain LC_ID_DYLIB. ld64's code
seems to treat bundles and dylibs identically in most places.

Supporting bundles allows us to run e.g. XCTests, as all test suites are
compiled into bundles which get dynamically loaded by the xctest test runner.

[int3]

fix test

[int3]

extend test

[int3]

use getLastArg

[smeenai]

LGTM

lld/MachO/Driver.cpp

 }
 
 void MachOOptTable::printHelp(const char *argv0, bool showHidden) const {
   PrintHelp(lld::outs(), (std::string(argv0) + " [options] file...").c_str(),
             "LLVM Linker", showHidden);
   lld::outs() << "\n";
 }
 
+HeaderFileType getOutputType(const opt::InputArgList &args) {
+  // TODO: -r, -dylinker, -preload...
+  opt::Arg *outputArg = args.getLastArg(OPT_bundle, OPT_dylib, OPT_execute);
+  if (outputArg == nullptr)
+    return MH_EXECUTE;
+
+  switch (outputArg->getOption().getID()) {
+  case OPT_bundle:
+    return MH_BUNDLE;
+  case OPT_dylib:
+    return MH_DYLIB;
+  case OPT_execute:
+    return MH_EXECUTE;
+  default:
+    llvm_unreachable("internal error");
+  }
+}
+
 static Optional<std::string>
 findAlongPathsWithExtensions(StringRef name, ArrayRef<StringRef> extensions) {
   llvm::SmallString<261> base;
   for (StringRef dir : config->librarySearchPaths) {
     base = dir;
     path::append(base, Twine("lib") + name);
     for (StringRef ext : extensions) {
       Twine location = base + ext;
bool macho::link(llvm::ArrayRef<const char *> argsArr, bool canExitEarly,
 
   config->entry = symtab->addUndefined(args.getLastArgValue(OPT_e, "_main"));
   config->outputFile = args.getLastArgValue(OPT_o, "a.out");
   config->installName =
       args.getLastArgValue(OPT_install_name, config->outputFile);
   config->headerPad = args::getHex(args, OPT_headerpad, /*Default=*/32);
   config->headerPadMaxInstallNames =
       args.hasArg(OPT_headerpad_max_install_names);
-  config->outputType = args.hasArg(OPT_dylib) ? MH_DYLIB : MH_EXECUTE;
+  config->outputType = getOutputType(args);
   config->runtimePaths = args::getStrings(args, OPT_rpath);
   config->allLoad = args.hasArg(OPT_all_load);
   config->forceLoadObjC = args.hasArg(OPT_ObjC);
 
   if (const opt::Arg *arg = args.getLastArg(OPT_static, OPT_dynamic))
     config->staticLink = (arg->getOption().getID() == OPT_static);
 
   config->systemLibraryRoots = getSystemLibraryRoots(args);
case OPT_platform_version:
       handlePlatformVersion(arg);
       break;
     default:
       break;
     }
   }
 
   config->isPic = config->outputType == MH_DYLIB ||
+                  config->outputType == MH_BUNDLE ||
                   (config->outputType == MH_EXECUTE && args.hasArg(OPT_pie));
 
   // Now that all dylibs have been loaded, search for those that should be
   // re-exported.
   for (opt::Arg *arg : args.filtered(OPT_sub_library)) {
     config->hasReexports = true;
     StringRef searchName = arg->getValue();
     if (!markSubLibrary(searchName))

lld/MachO/Writer.cpp

void Writer::createLoadCommands() {
   switch (config->outputType) {
   case MH_EXECUTE:
     in.header->addLoadCommand(make<LCMain>());
     in.header->addLoadCommand(make<LCLoadDylinker>());
     break;
   case MH_DYLIB:
     in.header->addLoadCommand(make<LCDylib>(LC_ID_DYLIB, config->installName));
     break;
+  case MH_BUNDLE:
+    break;
   default:
     llvm_unreachable("unhandled output file type");
   }
 
   in.header->addLoadCommand(make<LCBuildVersion>(config->platform));
 
   uint8_t segIndex = 0;
   for (OutputSegment *seg : outputSegments) {
void Writer::createOutputSections() {
   symtabSection = make<SymtabSection>(*stringTableSection);
   indirectSymtabSection = make<IndirectSymtabSection>();
 
   switch (config->outputType) {
   case MH_EXECUTE:
     make<PageZeroSection>();
     break;
   case MH_DYLIB:
+  case MH_BUNDLE:
     break;
   default:
     llvm_unreachable("unhandled output file type");
   }
 
   // Then merge input sections into output sections.
   MapVector<std::pair<StringRef, StringRef>, MergedOutputSection *>
       mergedOutputSections;

lld/test/MachO/load-commands.s

 # REQUIRES: x86
-# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %s -o %t.o
-# RUN: lld -flavor darwinnew -o %t %t.o
+# RUN: rm -rf %t && mkdir -p %t
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %s -o %t/test.o
+# RUN: lld -flavor darwinnew -o %t/executable %t/test.o
+# RUN: lld -flavor darwinnew -bundle -o %t/bundle %t/test.o
+# RUN: lld -flavor darwinnew -dylib -o %t/dylib %t/test.o
+
+## These load commands should be in every final output binary.
+# COMMON-DAG: cmd LC_DYLD_INFO_ONLY
+# COMMON-DAG: cmd LC_SYMTAB
+# COMMON-DAG: cmd LC_DYSYMTAB
 
 ## Check for the presence of load commands that are essential for a working
-## executable.
-# RUN: llvm-objdump --macho --all-headers %t | FileCheck %s
-# CHECK-DAG: cmd LC_DYLD_INFO_ONLY
-# CHECK-DAG: cmd LC_SYMTAB
-# CHECK-DAG: cmd LC_DYSYMTAB
-# CHECK-DAG: cmd LC_MAIN
-# CHECK-DAG: cmd LC_LOAD_DYLINKER
+## executable. Also check that it has the right filetype.
+# RUN: llvm-objdump --macho --all-headers %t/executable | FileCheck %s --check-prefix=COMMON
+# RUN: llvm-objdump --macho --all-headers %t/executable | FileCheck %s --check-prefix=EXEC
+# EXEC:      magic        cputype cpusubtype  caps    filetype
+# EXEC-NEXT: MH_MAGIC_64  X86_64         ALL  {{.*}}  EXECUTE
+# EXEC-DAG:  cmd LC_MAIN
+# EXEC-DAG:  cmd LC_LOAD_DYLINKER
 
 ## Check for the absence of load commands that should not be in an executable.
-# RUN: llvm-objdump --macho --all-headers %t | FileCheck %s --check-prefix=NCHECK
-# NCHECK-NOT: cmd: LC_ID_DYLIB
+# RUN: llvm-objdump --macho --all-headers %t/executable | FileCheck %s --check-prefix=NEXEC
+# NEXEC-NOT: cmd: LC_ID_DYLIB
+
+## Check for the presence / absence of load commands for the dylib.
+# RUN: llvm-objdump --macho --all-headers %t/dylib | FileCheck %s --check-prefix=COMMON
+# RUN: llvm-objdump --macho --all-headers %t/dylib | FileCheck %s --check-prefix=DYLIB
+# DYLIB:      magic        cputype cpusubtype  caps    filetype
+# DYLIB-NEXT: MH_MAGIC_64  X86_64         ALL  {{.*}}  DYLIB
+# DYLIB:      cmd LC_ID_DYLIB
+
+# RUN: llvm-objdump --macho --all-headers %t/bundle | FileCheck %s --check-prefix=NDYLIB
+# NDYLIB-NOT: cmd: LC_MAIN
+# NDYLIB-NOT: cmd: LC_LOAD_DYLINKER
+
+## Check for the presence / absence of load commands for the bundle.
+# RUN: llvm-objdump --macho --all-headers %t/bundle | FileCheck %s --check-prefix=COMMON
+# RUN: llvm-objdump --macho --all-headers %t/bundle | FileCheck %s --check-prefix=BUNDLE
+# BUNDLE:      magic        cputype cpusubtype  caps    filetype
+# BUNDLE-NEXT: MH_MAGIC_64  X86_64         ALL  {{.*}}  BUNDLE
+
+# RUN: llvm-objdump --macho --all-headers %t/bundle | FileCheck %s --check-prefix=NBUNDLE
+# NBUNDLE-NOT: cmd: LC_MAIN
+# NBUNDLE-NOT: cmd: LC_LOAD_DYLINKER
 
 .text
 .global _main
 _main:
   mov $0, %rax
   ret