Allow pnacl-freeze/thaw to redirect to stdin/stdout.

tools/pnacl-freeze/pnacl-freeze.cpp

 /* Copyright 2013 The Native Client Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can
  * be found in the LICENSE file.
  */
 
 //===-- pnacl-freeze.cpp - The low-level NaCl bitcode freezer     --------===//
 //
 //===----------------------------------------------------------------------===//
 //
 // Generates NaCl pexe wire format.
@@ skipping 16 matching lines @@
 #include "llvm/Support/ToolOutputFile.h"
 
 using namespace llvm;
 
 
 static cl::opt<std::string>
 OutputFilename("o", cl::desc("Specify output filename"),
                cl::value_desc("filename"));
 
 static cl::opt<std::string>
-InputFilename(cl::Positional, cl::desc("<pexe file>"), cl::Required);
+InputFilename(cl::Positional, cl::desc("<pexe file>"), cl::init("-"));
 
 static void WriteOutputFile(const Module *M) {
 
-  std::string FrozenFilename =
-    (OutputFilename.size() == 0 ? (InputFilename + ".frozen") : OutputFilename);
+  std::string FrozenFilename(OutputFilename);
+  if (OutputFilename.size() == 0) {
+    std::string input_filename;
+    if (InputFilename == "-")
+      input_filename = "<stdin>";

[jvoung (off chromium), 2013/05/02 22:12:50]

What some of the other tools do is set OutputFilename to be "-" also, in the
case Input is "-" and Output is not specified.  That might be simpler than this,
since this would leave a file with funny characters "<stdin>.frozen" in its
name?

[Karl, 2013/05/06 16:21:51]

I guess this is ok. I just have to redirect my mind to think in terms of pipes.
Changing.

+    else
+      input_filename = InputFilename;
+    FrozenFilename = input_filename + ".frozen";
+  }
 
   std::string ErrorInfo;
   OwningPtr<tool_output_file> Out
     (new tool_output_file(FrozenFilename.c_str(), ErrorInfo,
                           raw_fd_ostream::F_Binary));
   if (!ErrorInfo.empty()) {
     errs() << ErrorInfo << '\n';
     exit(1);
   }
 
@@ skipping 12 matching lines @@
   llvm_shutdown_obj Y;  // Call llvm_shutdown() on exit.
 
   cl::ParseCommandLineOptions(argc, argv, "Generates NaCl pexe wire format\n");
 
   std::string ErrorMessage;
   std::auto_ptr<Module> M;
 
   // Use the bitcode streaming interface
   DataStreamer *streamer = getDataFileStreamer(InputFilename, &ErrorMessage);
   if (streamer) {
-    std::string DisplayFilename = InputFilename;
+    std::string DisplayFilename;
+    if (InputFilename == "-")
+      DisplayFilename = "<stdin>";
+    else
+      DisplayFilename = InputFilename;
     M.reset(getStreamedBitcodeModule(DisplayFilename, streamer, Context,
                                      &ErrorMessage));
     if(M.get() != 0 && M->MaterializeAllPermanently(&ErrorMessage)) {
       M.reset();
     }
   }
 
   if (M.get() == 0) {
     errs() << argv[0] << ": ";
     if (ErrorMessage.size())
       errs() << ErrorMessage << "\n";
     else
       errs() << "bitcode didn't read correctly.\n";
     return 1;
   }
 
   WriteOutputFile(M.get());
   return 0;
 }