[llvm-objcopy][MachO] Implement --only-section

Reviewers: alexshap, rupprecht, jdoerfert, jhenderson

Reviewed By: alexshap, rupprecht, jhenderson

Subscribers: mgorny, jakehehrlich, abrachet, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D65541
diff --git a/llvm/tools/llvm-objcopy/MachO/MachOObjcopy.cpp b/llvm/tools/llvm-objcopy/MachO/MachOObjcopy.cpp
index 6d586e7..73983a1 100644
--- a/llvm/tools/llvm-objcopy/MachO/MachOObjcopy.cpp
+++ b/llvm/tools/llvm-objcopy/MachO/MachOObjcopy.cpp
@@ -18,6 +18,19 @@
 namespace macho {
 
 using namespace object;
+using SectionPred = std::function<bool(const Section &Sec)>;
+
+static void removeSections(const CopyConfig &Config, Object &Obj) {
+  SectionPred RemovePred = [](const Section &) { return false; };
+
+  if (!Config.OnlySection.empty()) {
+    RemovePred = [&Config, RemovePred](const Section &Sec) {
+      return !Config.OnlySection.matches(Sec.CanonicalName);
+    };
+  }
+
+  return Obj.removeSections(RemovePred);
+}
 
 static Error handleArgs(const CopyConfig &Config, Object &Obj) {
   if (Config.AllowBrokenLinks || !Config.BuildIdLinkDir.empty() ||
@@ -25,11 +38,10 @@
       !Config.SplitDWO.empty() || !Config.SymbolsPrefix.empty() ||
       !Config.AllocSectionsPrefix.empty() || !Config.AddSection.empty() ||
       !Config.DumpSection.empty() || !Config.KeepSection.empty() ||
-      Config.NewSymbolVisibility || !Config.OnlySection.empty() ||
-      !Config.SymbolsToGlobalize.empty() || !Config.SymbolsToKeep.empty() ||
-      !Config.SymbolsToLocalize.empty() || !Config.SymbolsToWeaken.empty() ||
-      !Config.SymbolsToKeepGlobal.empty() || !Config.SectionsToRename.empty() ||
-      !Config.SymbolsToRename.empty() ||
+      Config.NewSymbolVisibility || !Config.SymbolsToGlobalize.empty() ||
+      !Config.SymbolsToKeep.empty() || !Config.SymbolsToLocalize.empty() ||
+      !Config.SymbolsToWeaken.empty() || !Config.SymbolsToKeepGlobal.empty() ||
+      !Config.SectionsToRename.empty() || !Config.SymbolsToRename.empty() ||
       !Config.UnneededSymbolsToRemove.empty() ||
       !Config.SetSectionAlignment.empty() || !Config.SetSectionFlags.empty() ||
       !Config.ToRemove.empty() || Config.ExtractDWO || Config.KeepFileSymbols ||
@@ -43,6 +55,7 @@
                              "option not supported by llvm-objcopy for MachO");
   }
 
+  removeSections(Config, Obj);
   return Error::success();
 }