[llvm-readobj] Print error when executed with no input files

This patch changes llvm-readelf (and llvm-readobj for consistency)
behavior to print an error when executed with no input files.

Reading from stdin can be achieved via a '-' for the input
object.

Fixes https://bugs.llvm.org/show_bug.cgi?id=46400

Differential Revision: https://reviews.llvm.org/D83704

Reviewed by: jhenderson, MaskRay, sbc, jyknight

1 files changed, 5 insertions, 4 deletions

diff --git a/llvm/tools/llvm-readobj/llvm-readobj.cpp b/llvm/tools/llvm-readobj/llvm-readobj.cpp
index b9c6ad2..6b8a883 100644
--- a/llvm/tools/llvm-readobj/llvm-readobj.cpp
+++ b/llvm/tools/llvm-readobj/llvm-readobj.cpp
@@ -690,6 +690,11 @@ int main(int argc, const char *argv[]) {
 
   cl::ParseCommandLineOptions(argc, argv, "LLVM Object Reader\n");
 
+  // Default to print error if no filename is specified.
+  if (opts::InputFilenames.empty()) {
+    error("no input files specified");
+  }
+
   if (opts::All) {
     opts::FileHeaders = true;
     opts::ProgramHeaders = true;
@@ -714,10 +719,6 @@ int main(int argc, const char *argv[]) {
     opts::SectionHeaders = true;
   }
 
-  // Default to stdin if no filename is specified.
-  if (opts::InputFilenames.empty())
-    opts::InputFilenames.push_back("-");
-
   ScopedPrinter Writer(fouts());
   for (const std::string &I : opts::InputFilenames)
     dumpInput(I, Writer);