[llvm-readobj] Support -needed-libs option for Mach-O files

This implements the -needed-libs option in Mach-O dumper.

Differential Revision: https://reviews.llvm.org/D41527

llvm-svn: 321980

llvm/test/tools/llvm-readobj/macho-needed-libs.test

@@ -0,0 +1,26 @@
+# RUN: yaml2obj %s -o %t.o
+# RUN: llvm-readobj -needed-libs %t.o | FileCheck %s
+
+# CHECK:      NeededLibraries [
+# CHECK-NEXT:   /usr/lib/libSystem.B.dylib
+# CHECK-NEXT: ]
+
+!mach-o
+FileHeader:
+  magic:           0xFEEDFACF
+  cputype:         0x01000007
+  cpusubtype:      0x00000003
+  filetype:        0x00000001
+  ncmds:           1
+  sizeofcmds:      56
+  flags:           0x00002000
+  reserved:        0x00000000
+LoadCommands:
+  - cmd:             LC_LOAD_DYLIB
+    cmdsize:         56
+    dylib:
+      name:            24
+      timestamp:       2
+      current_version: 81985536
+      compatibility_version: 65536
+    PayloadString:   /usr/lib/libSystem.B.dylib

llvm/tools/llvm-readobj/MachODumper.cpp

@@ -39,6 +39,8 @@ public:
   void printUnwindInfo() override;
   void printStackMap() const override;
 
+  void printNeededLibraries() override;
+
   // MachO-specific.
   void printMachODataInCode() override;
   void printMachOVersionMin() override;
@@ -675,6 +677,34 @@ void MachODumper::printStackMap() const {
                          StackMapV2Parser<support::big>(StackMapContentsArray));
 }
 
+void MachODumper::printNeededLibraries() {
+  ListScope D(W, "NeededLibraries");
+
+  using LibsTy = std::vector<StringRef>;
+  LibsTy Libs;
+
+  for (const auto &Command : Obj->load_commands()) {
+    if (Command.C.cmd == MachO::LC_LOAD_DYLIB ||
+        Command.C.cmd == MachO::LC_ID_DYLIB ||
+        Command.C.cmd == MachO::LC_LOAD_WEAK_DYLIB ||
+        Command.C.cmd == MachO::LC_REEXPORT_DYLIB ||
+        Command.C.cmd == MachO::LC_LAZY_LOAD_DYLIB ||
+        Command.C.cmd == MachO::LC_LOAD_UPWARD_DYLIB) {
+      MachO::dylib_command Dl = Obj->getDylibIDLoadCommand(Command);
+      if (Dl.dylib.name < Dl.cmdsize) {
+        auto *P = static_cast<const char*>(Command.Ptr) + Dl.dylib.name;
+        Libs.push_back(P);
+      }
+    }
+  }
+
+  std::stable_sort(Libs.begin(), Libs.end());
+
+  for (const auto &L : Libs) {
+    outs() << "  " << L << "\n";
+  }
+}
+
 void MachODumper::printMachODataInCode() {
   for (const auto &Load : Obj->load_commands()) {
     if (Load.C.cmd  == MachO::LC_DATA_IN_CODE) {