Convenience/safety fix for llvm::sys::Execute(And|No)Wait

Summary:
Change the type of the Redirects parameter of llvm::sys::ExecuteAndWait,
ExecuteNoWait and other APIs that wrap them from `const StringRef **` to
`ArrayRef<Optional<StringRef>>`, which is safer and simplifies the use of these
APIs (no more local StringRef variables just to get a pointer to).

Corresponding clang changes will be posted as a separate patch.

Reviewers: bkramer

Reviewed By: bkramer

Subscribers: vsk, llvm-commits

Differential Revision: https://reviews.llvm.org/D37563

llvm-svn: 313155

1 files changed, 7 insertions, 5 deletions

diff --git a/llvm/tools/bugpoint/OptimizerDriver.cpp b/llvm/tools/bugpoint/OptimizerDriver.cpp
index 489e50b8810..0b22f1b729a 100644
--- a/llvm/tools/bugpoint/OptimizerDriver.cpp
+++ b/llvm/tools/bugpoint/OptimizerDriver.cpp
@@ -230,13 +230,15 @@ bool BugDriver::runPasses(Module *Program,
         << " " << Args[i];
         errs() << "\n";);
 
-  // Redirect stdout and stderr to nowhere if SilencePasses is given
-  StringRef Nowhere;
-  const StringRef *Redirects[3] = {nullptr, &Nowhere, &Nowhere};
+  Optional<StringRef> Redirects[3] = {None, None, None};
+  // Redirect stdout and stderr to nowhere if SilencePasses is given.
+  if (SilencePasses) {
+    Redirects[1] = "";
+    Redirects[2] = "";
+  }
 
   std::string ErrMsg;
-  int result = sys::ExecuteAndWait(Prog, Args.data(), nullptr,
-                                   (SilencePasses ? Redirects : nullptr),
+  int result = sys::ExecuteAndWait(Prog, Args.data(), nullptr, Redirects,
                                    Timeout, MemoryLimit, &ErrMsg);
 
   // If we are supposed to delete the bitcode file or if the passes crashed,