[lld-macho] Support -sub_umbrella

[int3]

Summary

From what I can tell, it's essentially identical to
-sub_library, but it doesn't match files ending in ".dylib".

[thakis]

lgtm. Below is what I checked:

Doesn't sub_umbrella cause a different load command? (LC_SUB_UMBRELLA, sub_umbrella_command -- which admittedly has the same in-memory repr as sub_library_command, but the cmd id is different)

% touch foo.cc
% clang foo.cc -c
% clang -shared -o foo.dylib foo.o
% clang -shared -o bar.dylib foo.o -sub_umbrella foo.dylib foo.dylib
% otool -l bar.dylib | grep -C5 foo.dylib
  cmdsize 16
  version 0.0
Load command 9
          cmd LC_REEXPORT_DYLIB
      cmdsize 40
         name foo.dylib (offset 24)
   time stamp 2 Wed Dec 31 19:00:02 1969
      current version 0.0.0
compatibility version 0.0.0
Load command 10
          cmd LC_LOAD_DYLIB

…no, it's just a LC_REEXPORT_DYLIB. Looking through ld64, that seems to match the handling there (but looking for it made me find -debug_snapshot / -snapshot_dir which I didn't know before. I guess that's like our --reproduce? If so, that'd be exciting! I'll add support for that spelling of --reproduce then, similar to how the coff port has both /reproduce: and /linkrepro:, the latter to match link.exe). So this looks correct.

[int3]

There's a comment in ld64 that says

// target OS does not support LC_REEXPORT_DYLIB, so use old complicated load commands

So I guess that's what LC_SUB_{UMBRELLA, LIBRARY} are.

[int3]

And yup, the snapshot arguments look similar to our --reproduce

lld/MachO/Driver.cpp

for (StringRef rest : args::getLines(mbref)) {
     --priority;
   }
 }
 
 // We expect sub-library names of the form "libfoo", which will match a dylib
 // with a path of .*/libfoo.{dylib, tbd}.
 // XXX ld64 seems to ignore the extension entirely when matching sub-libraries;
 // I'm not sure what the use case for that is.
-static bool markSubLibrary(StringRef searchName) {
+static bool markReexport(StringRef searchName, ArrayRef<StringRef> extensions) {
   for (InputFile *file : inputFiles) {
     if (auto *dylibFile = dyn_cast<DylibFile>(file)) {
       StringRef filename = path::filename(dylibFile->getName());
       if (filename.consume_front(searchName) &&
-          (filename == ".dylib" || filename == ".tbd")) {
+          (filename.empty() ||
+           find(extensions, filename) != extensions.end())) {
         dylibFile->reexport = true;
         return true;
       }
     }
   }
   return false;
 }
 
for (const auto &arg : args) {
     }
   }
 
   config->isPic = config->outputType == MH_DYLIB ||
                   config->outputType == MH_BUNDLE || isPie(args);
 
   // Now that all dylibs have been loaded, search for those that should be
   // re-exported.
-  for (opt::Arg *arg : args.filtered(OPT_sub_library)) {
+  for (opt::Arg *arg : args.filtered(OPT_sub_library, OPT_sub_umbrella)) {
     config->hasReexports = true;
     StringRef searchName = arg->getValue();
-    if (!markSubLibrary(searchName))
-      error("-sub_library " + searchName + " does not match a supplied dylib");
+    std::vector<StringRef> extensions;
+    if (arg->getOption().getID() == OPT_sub_library)
+      extensions = {".dylib", ".tbd"};
+    else
+      extensions = {".tbd"};
+    if (!markReexport(searchName, extensions))
+      error(arg->getSpelling() + " " + searchName +
+            " does not match a supplied dylib");
   }
 
   // Parse LTO options.
   if (auto *arg = args.getLastArg(OPT_mcpu))
     parseClangOption(saver.save("-mcpu=" + StringRef(arg->getValue())),
                      arg->getSpelling());
 
   for (auto *arg : args.filtered(OPT_mllvm))

lld/MachO/Options.td

def init : Separate<["-"], "init">,
      Group<grp_rare>;
 def sub_library : Separate<["-"], "sub_library">,
      MetaVarName<"<name>">,
      HelpText<"Re-export the dylib as <name>">,
      Group<grp_rare>;
 def sub_umbrella : Separate<["-"], "sub_umbrella">,
      MetaVarName<"<name>">,
      HelpText<"Re-export the framework as <name>">,
-     Flags<[HelpHidden]>,
      Group<grp_rare>;
 def allowable_client : Separate<["-"], "allowable_client">,
      MetaVarName<"<name>">,
      HelpText<"Specify <name> of a dylib or framework that is allowed to link to this dylib">,
      Flags<[HelpHidden]>,
      Group<grp_rare>;
 def client_name : Separate<["-"], "client_name">,
      MetaVarName<"<name>">,

lld/test/MachO/sub-library.s

 
 ## Check that they have the appropriate LC_REEXPORT_DYLIB commands, and that
 ## NO_REEXPORTED_DYLIBS is (un)set as appropriate.
 
 # RUN: llvm-objdump --macho --all-headers %t/libhello.dylib | FileCheck %s \
 # RUN:   --check-prefix=HELLO-HEADERS
 # HELLO-HEADERS: NO_REEXPORTED_DYLIBS
 
-# RUN: llvm-objdump --macho --all-headers %t/libgoodbye.dylib | FileCheck %s -DDIR=%t \
-# RUN:   --check-prefix=GOODBYE-HEADERS
-# GOODBYE-HEADERS-NOT: NO_REEXPORTED_DYLIBS
-# GOODBYE-HEADERS:     cmd     LC_REEXPORT_DYLIB
-# GOODBYE-HEADERS-NOT: Load command
-# GOODBYE-HEADERS:     name    [[DIR]]/libhello.dylib
-
-# RUN: llvm-objdump --macho --all-headers %t/libsuper.dylib | FileCheck %s -DDIR=%t \
-# RUN:   --check-prefix=SUPER-HEADERS
-# SUPER-HEADERS-NOT: NO_REEXPORTED_DYLIBS
-# SUPER-HEADERS:     cmd     LC_REEXPORT_DYLIB
-# SUPER-HEADERS-NOT: Load command
-# SUPER-HEADERS:     name    [[DIR]]/libgoodbye.dylib
+# RUN: llvm-objdump --macho --all-headers %t/libgoodbye.dylib | FileCheck %s \
+# RUN:   --check-prefix=REEXPORT-HEADERS -DPATH=%t/libhello.dylib
+
+# RUN: llvm-objdump --macho --all-headers %t/libsuper.dylib | FileCheck %s \
+# RUN:   --check-prefix=REEXPORT-HEADERS -DPATH=%t/libgoodbye.dylib
+
+# REEXPORT-HEADERS-NOT: NO_REEXPORTED_DYLIBS
+# REEXPORT-HEADERS:     cmd     LC_REEXPORT_DYLIB
+# REEXPORT-HEADERS-NOT: Load command
+# REEXPORT-HEADERS:     name    [[PATH]]
 
 # RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %s -o %t/sub-library.o
 # RUN: %lld -o %t/sub-library -L%t -lsuper %t/sub-library.o
 
 # RUN: llvm-objdump --macho --bind %t/sub-library | FileCheck %s
 # CHECK-LABEL: Bind table:
 # CHECK-DAG:   __DATA_CONST __got {{.*}} libsuper _hello_world
 # CHECK-DAG:   __DATA_CONST __got {{.*}} libsuper _goodbye_world
 
 
 ## Check that we fail gracefully if the sub-library is missing
 # RUN: not %lld -dylib -o %t/sub-library -sub_library libmissing %t/sub-library.o 2>&1 \
 # RUN:   | FileCheck %s --check-prefix=MISSING-SUB-LIBRARY
 # MISSING-SUB-LIBRARY: error: -sub_library libmissing does not match a supplied dylib
 # RUN: rm -f %t/libgoodbye.dylib
 # RUN: not %lld -o %t/sub-library -L%t -lsuper %t/sub-library.o 2>&1 \
 # RUN:  | FileCheck %s --check-prefix=MISSING-REEXPORT -DDIR=%t
 # MISSING-REEXPORT: error: unable to locate re-export with install name [[DIR]]/libgoodbye.dylib
 
+
+## We can match dylibs without extensions too.
+# RUN: mkdir -p %t/Hello.framework/Versions
+# RUN: %lld -dylib %t/libhello.o -o %t/Hello.framework/Versions/Hello
+# RUN: %lld -dylib -o %t/libgoodbye2.dylib -sub_library Hello %t/Hello.framework/Versions/Hello %t/libgoodbye.o
+# RUN: llvm-objdump --macho --all-headers %t/libgoodbye2.dylib | FileCheck %s \
+# RUN:   --check-prefix=REEXPORT-HEADERS -DPATH=%t/Hello.framework/Versions/Hello
+
+## -sub_umbrella works almost identically...
+# RUN: %lld -dylib -o %t/libgoodbye3.dylib -sub_umbrella Hello %t/Hello.framework/Versions/Hello %t/libgoodbye.o
+# RUN: llvm-objdump --macho --all-headers %t/libgoodbye3.dylib | FileCheck %s \
+# RUN:   --check-prefix=REEXPORT-HEADERS -DPATH=%t/Hello.framework/Versions/Hello
+
+## But it doesn't match .dylib extensions:
+# RUN: not %lld -dylib -L%t -sub_umbrella libhello -lhello %t/libgoodbye.o \
+# RUN:   -o %t/libgoodbye.dylib 2>&1 | FileCheck %s --check-prefix=MISSING-FRAMEWORK
+# MISSING-FRAMEWORK: error: -sub_umbrella libhello does not match a supplied dylib
+
 .text
 .globl _main
 
 _main:
   movl $0x2000004, %eax # write() syscall
   mov $1, %rdi # stdout
   movq _hello_world@GOTPCREL(%rip), %rsi
   mov $13, %rdx # length of str