Fix SupportsSeeking detection on windows.

Will be tested by existing tests once used (soon).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@234737 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Support/raw_ostream.cpp b/lib/Support/raw_ostream.cpp
index b8588af702bb65817e0cf27772a684908d9e7aa0..16c52c90e09048741ad8d29d5de3d4d98657a526 100644 (file)
--- a/lib/Support/raw_ostream.cpp
+++ b/lib/Support/raw_ostream.cpp
@@ -525,7 +525,14 @@ raw_fd_ostream::raw_fd_ostream(int fd, bool shouldClose, bool unbuffered)
 
   // Get the starting position.
   off_t loc = ::lseek(FD, 0, SEEK_CUR);
+#ifdef LLVM_ON_WIN32
+  // MSVCRT's _lseek(SEEK_CUR) doesn't return -1 for pipes.
+  sys::fs::file_status Status;
+  std::error_code EC = status(FD, Status);
+  SupportsSeeking = !EC && Status.type() == sys::fs::file_type::regular_file;
+#else
   SupportsSeeking = loc != (off_t)-1;
+#endif
   if (!SupportsSeeking)
     pos = 0;
   else