[llvm-objcopy] Make modifications in-place if output is not specified

If the output file is not specified make the modifications in-place 
(like binutils objcopy does). In particular, this fixes 
the behavior of Clang -gsplit-dwarf (if Clang is configured to use llvm-objcopy), 
previously it was creating .dwo files, but still leaving *dwo* sections in 
the original binary.

Test plan: make check-all

Differential revision: https://reviews.llvm.org/D42873

llvm-svn: 324783

1 files changed, 5 insertions, 3 deletions

diff --git a/llvm/tools/llvm-objcopy/llvm-objcopy.cpp b/llvm/tools/llvm-objcopy/llvm-objcopy.cpp
index 8f5243cefa0..7d230390872 100644
--- a/llvm/tools/llvm-objcopy/llvm-objcopy.cpp
+++ b/llvm/tools/llvm-objcopy/llvm-objcopy.cpp
@@ -72,8 +72,8 @@ LLVM_ATTRIBUTE_NORETURN void reportError(StringRef File, Error E) {
 } // end namespace llvm
 
 static cl::opt<std::string> InputFilename(cl::Positional, cl::desc("<input>"));
-static cl::opt<std::string> OutputFilename(cl::Positional, cl::desc("<output>"),
-                                           cl::init("-"));
+static cl::opt<std::string> OutputFilename(cl::Positional, cl::desc("[ <output> ]"));
+
 static cl::opt<std::string>
     OutputFormat("O", cl::desc("Set output format to one of the following:"
                                "\n\tbinary"));
@@ -340,7 +340,9 @@ int main(int argc, char **argv) {
 
   auto Reader = CreateReader();
   auto Obj = Reader->create();
-  auto Writer = CreateWriter(*Obj, OutputFilename);
+  StringRef Output =
+      OutputFilename.getNumOccurrences() ? OutputFilename : InputFilename;
+  auto Writer = CreateWriter(*Obj, Output);
   HandleArgs(*Obj, *Reader);
   Writer->finalize();
   Writer->write();