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, 5 insertions, 4 deletions

diff --git a/llvm/lib/Support/Windows/Program.inc b/llvm/lib/Support/Windows/Program.inc
index f9000d2d741..52921cd6a20 100644
--- a/llvm/lib/Support/Windows/Program.inc
+++ b/llvm/lib/Support/Windows/Program.inc
@@ -103,9 +103,10 @@ ErrorOr<std::string> sys::findProgramByName(StringRef Name,
   return std::string(U8Result.begin(), U8Result.end());
 }
 
-static HANDLE RedirectIO(const StringRef *Path, int fd, std::string* ErrMsg) {
+static HANDLE RedirectIO(Optional<StringRef> Path, int fd,
+                         std::string *ErrMsg) {
   HANDLE h;
-  if (Path == 0) {
+  if (!Path) {
     if (!DuplicateHandle(GetCurrentProcess(), (HANDLE)_get_osfhandle(fd),
                          GetCurrentProcess(), &h,
                          0, TRUE, DUPLICATE_SAME_ACCESS))
@@ -249,7 +250,7 @@ static std::unique_ptr<char[]> flattenArgs(const char **Args) {
 }
 
 static bool Execute(ProcessInfo &PI, StringRef Program, const char **Args,
-                    const char **Envp, const StringRef **Redirects,
+                    const char **Envp, ArrayRef<Optional<StringRef>> Redirects,
                     unsigned MemoryLimit, std::string *ErrMsg) {
   if (!sys::fs::can_execute(Program)) {
     if (ErrMsg)
@@ -299,7 +300,7 @@ static bool Execute(ProcessInfo &PI, StringRef Program, const char **Args,
   si.hStdOutput = INVALID_HANDLE_VALUE;
   si.hStdError = INVALID_HANDLE_VALUE;
 
-  if (Redirects) {
+  if (!Redirects.empty()) {
     si.dwFlags = STARTF_USESTDHANDLES;
 
     si.hStdInput = RedirectIO(Redirects[0], 0, ErrMsg);