[lld-macho] Make it possible to re-export .tbd files

Two things needed fixing for that to work:

1. getName() no longer returns null for DylibFiles constructed from TAPIs
2. markSubLibrary() now accepts .tbd as a possible extension

Differential Revision: https://reviews.llvm.org/D86180

lld/MachO/Driver.cpp

@@ -379,12 +379,15 @@ static void parseOrderFile(StringRef path) {
 }
 
 // We expect sub-library names of the form "libfoo", which will match a dylib
-// with a path of .*/libfoo.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) {
   for (InputFile *file : inputFiles) {
     if (auto *dylibFile = dyn_cast<DylibFile>(file)) {
       StringRef filename = path::filename(dylibFile->getName());
-      if (filename.consume_front(searchName) && filename == ".dylib") {
+      if (filename.consume_front(searchName) &&
+          (filename == ".dylib" || filename == ".tbd")) {
         dylibFile->reexport = true;
         return true;
       }

lld/MachO/InputFiles.cpp

@@ -397,7 +397,7 @@ DylibFile::DylibFile(MemoryBufferRef mb, DylibFile *umbrella)
 }
 
 DylibFile::DylibFile(const InterfaceFile &interface, DylibFile *umbrella)
-    : InputFile(DylibKind, MemoryBufferRef()) {
+    : InputFile(DylibKind, interface) {
   if (umbrella == nullptr)
     umbrella = this;
 

lld/MachO/InputFiles.h

@@ -12,6 +12,7 @@
 #include "MachOStructs.h"
 
 #include "lld/Common/LLVM.h"
+#include "lld/Common/Memory.h"
 #include "llvm/ADT/DenseSet.h"
 #include "llvm/BinaryFormat/MachO.h"
 #include "llvm/Object/Archive.h"
@@ -45,15 +46,19 @@ class InputFile {
 
   virtual ~InputFile() = default;
   Kind kind() const { return fileKind; }
-  StringRef getName() const { return mb.getBufferIdentifier(); }
+  StringRef getName() const { return name; }
 
   MemoryBufferRef mb;
   std::vector<Symbol *> symbols;
   ArrayRef<llvm::MachO::section_64> sectionHeaders;
   std::vector<SubsectionMap> subsections;
 
 protected:
-  InputFile(Kind kind, MemoryBufferRef mb) : mb(mb), fileKind(kind) {}
+  InputFile(Kind kind, MemoryBufferRef mb)
+      : mb(mb), fileKind(kind), name(mb.getBufferIdentifier()) {}
+
+  InputFile(Kind kind, const llvm::MachO::InterfaceFile &interface)
+      : fileKind(kind), name(saver.save(interface.getPath())) {}
 
   void parseSections(ArrayRef<llvm::MachO::section_64>);
 
@@ -64,6 +69,7 @@ class InputFile {
 
 private:
   const Kind fileKind;
+  const StringRef name;
 };
 
 // .o file
@@ -84,9 +90,6 @@ class OpaqueFile : public InputFile {
 // .dylib file
 class DylibFile : public InputFile {
 public:
-  explicit DylibFile(const llvm::MachO::InterfaceFile &interface,
-                     DylibFile *umbrella = nullptr);
-
   // Mach-O dylibs can re-export other dylibs as sub-libraries, meaning that the
   // symbols in those sub-libraries will be available under the umbrella
   // library's namespace. Those sub-libraries can also have their own
@@ -96,6 +99,9 @@ class DylibFile : public InputFile {
   // (through an -lfoo flag), then `umbrella` should be a nullptr.
   explicit DylibFile(MemoryBufferRef mb, DylibFile *umbrella = nullptr);
 
+  explicit DylibFile(const llvm::MachO::InterfaceFile &interface,
+                     DylibFile *umbrella = nullptr);
+
   static bool classof(const InputFile *f) { return f->kind() == DylibKind; }
 
   StringRef dylibName;

lld/test/MachO/Inputs/MacOSX.sdk/usr/lib/libc++.tbd

@@ -0,0 +1,10 @@
+--- !tapi-tbd-v3
+archs:            [ i386, x86_64 ]
+uuids:            [ 'i386: 00000000-0000-0000-0000-000000000000', 'x86_64: 00000000-0000-0000-0000-0
+0000000001' ]
+platform:         macosx
+install-name:     '/usr/lib/libc++.dylib'
+current-version:  1281
+exports:
+  - archs:        [ i386, x86_64 ]
+...

lld/test/MachO/reexport-stub.s

@@ -0,0 +1,12 @@
+# REQUIRES: x86
+# RUN: mkdir -p %t
+
+## This test verifies that a non-TBD dylib can re-export a TBD library.
+
+# RUN: echo "" | llvm-mc -filetype=obj -triple=x86_64-apple-darwin -o %t/reexporter.o
+# RUN: lld -flavor darwinnew -dylib -syslibroot %S/Inputs/MacOSX.sdk -lc++ -sub_library libc++ \
+# RUN:   %t/reexporter.o -o %t/libreexporter.dylib
+# RUN: llvm-objdump --macho --all-headers %t/libreexporter.dylib | FileCheck %s --check-prefix=DYLIB-HEADERS
+# DYLIB-HEADERS:     cmd     LC_REEXPORT_DYLIB
+# DYLIB-HEADERS-NOT: Load command
+# DYLIB-HEADERS:     name    /usr/lib/libc++.dylib