Refactor ExecuteAndWait to take StringRefs.

This simplifies some code which had StringRefs to begin with, and
makes other code more complicated which had const char* to begin
with.

In the end, I think this makes for a more idiomatic and platform
agnostic API.  Not all platforms launch process with null terminated
c-string arrays for the environment pointer and argv, but the api
was designed that way because it allowed easy pass-through for
posix-based platforms.  There's a little additional overhead now
since on posix based platforms we'll be takign StringRefs which
were constructed from null terminated strings and then copying
them to null terminate them again, but from a readability and
usability standpoint of the API user, I think this API signature
is strictly better.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@334518 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Driver/Job.cpp

@@ -317,22 +317,21 @@ int Command::Execute(ArrayRef<llvm::Optional<StringRef>> Redirects,
                      std::string *ErrMsg, bool *ExecutionFailed) const {
   SmallVector<const char*, 128> Argv;
 
-  const char **Envp;
-  if (Environment.empty()) {
-    Envp = nullptr;
-  } else {
+  Optional<ArrayRef<StringRef>> Env;
+  if (!Environment.empty()) {
     assert(Environment.back() == nullptr &&
            "Environment vector should be null-terminated by now");
-    Envp = const_cast<const char **>(Environment.data());
+    Env = llvm::toStringRefArray(Environment.data());
   }
 
   if (ResponseFile == nullptr) {
     Argv.push_back(Executable);
     Argv.append(Arguments.begin(), Arguments.end());
     Argv.push_back(nullptr);
 
+    auto Args = llvm::toStringRefArray(Argv.data());
     return llvm::sys::ExecuteAndWait(
-        Executable, Argv.data(), Envp, Redirects, /*secondsToWait*/ 0,
+        Executable, Args, Env, Redirects, /*secondsToWait*/ 0,
         /*memoryLimit*/ 0, ErrMsg, ExecutionFailed);
   }
 
@@ -357,7 +356,8 @@ int Command::Execute(ArrayRef<llvm::Optional<StringRef>> Redirects,
     return -1;
   }
 
-  return llvm::sys::ExecuteAndWait(Executable, Argv.data(), Envp, Redirects,
+  auto Args = llvm::toStringRefArray(Argv.data());
+  return llvm::sys::ExecuteAndWait(Executable, Args, Env, Redirects,
                                    /*secondsToWait*/ 0,
                                    /*memoryLimit*/ 0, ErrMsg, ExecutionFailed);
 }

lib/StaticAnalyzer/Frontend/AnalysisConsumer.cpp

@@ -883,9 +883,9 @@ UbigraphViz::~UbigraphViz() {
   std::string Ubiviz;
   if (auto Path = llvm::sys::findProgramByName("ubiviz"))
     Ubiviz = *Path;
-  const char *args[] = {Ubiviz.c_str(), Filename.c_str(), nullptr};
+  std::array<StringRef, 2> Args = {Ubiviz, Filename};
 
-  if (llvm::sys::ExecuteAndWait(Ubiviz, &args[0], nullptr, {}, 0, 0, &ErrMsg)) {
+  if (llvm::sys::ExecuteAndWait(Ubiviz, Args, llvm::None, {}, 0, 0, &ErrMsg)) {
     llvm::errs() << "Error viewing graph: " << ErrMsg << "\n";
   }
 

tools/clang-offload-bundler/ClangOffloadBundler.cpp

@@ -536,23 +536,22 @@ class ObjectFileHandler final : public FileHandler {
     // close it and use the name to pass down to clang.
     OS.close();
     SmallString<128> TargetName = getTriple(TargetNames[HostInputIndex]);
-    const char *ClangArgs[] = {"clang",
-                               "-r",
-                               "-target",
-                               TargetName.c_str(),
-                               "-o",
-                               OutputFileNames.front().c_str(),
-                               InputFileNames[HostInputIndex].c_str(),
-                               BitcodeFileName.c_str(),
-                               "-nostdlib",
-                               nullptr};
+    std::vector<StringRef> ClangArgs = {"clang",
+                                        "-r",
+                                        "-target",
+                                        TargetName.c_str(),
+                                        "-o",
+                                        OutputFileNames.front().c_str(),
+                                        InputFileNames[HostInputIndex].c_str(),
+                                        BitcodeFileName.c_str(),
+                                        "-nostdlib"};
 
     // If the user asked for the commands to be printed out, we do that instead
     // of executing it.
     if (PrintExternalCommands) {
       errs() << "\"" << ClangBinary.get() << "\"";
-      for (unsigned I = 1; ClangArgs[I]; ++I)
-        errs() << " \"" << ClangArgs[I] << "\"";
+      for (StringRef Arg : ClangArgs)
+        errs() << " \"" << Arg << "\"";
       errs() << "\n";
     } else {
       // Write the bitcode contents to the temporary file.