PR3478: raw_ostream should not buffer stderr

- Add unbuffered flag to raw_ostream, forwarded by raw_fd_ostream and
   used by raw_stderr_ostream.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@66545 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/raw_ostream.h

@@ -32,8 +32,10 @@ namespace llvm {
 class raw_ostream {
 protected:
   char *OutBufStart, *OutBufEnd, *OutBufCur;
+  bool Unbuffered;
+
 public:
-  raw_ostream() {
+  raw_ostream(bool unbuffered=false) : Unbuffered(unbuffered) {
     // Start out ready to flush.
     OutBufStart = OutBufEnd = OutBufCur = 0;
   }
@@ -59,6 +61,16 @@ public:
     OutBufCur = OutBufStart;
   }
 
+  /// SetUnbuffered - Set the streams buffering status. When
+  /// unbuffered the stream will flush after every write. This routine
+  /// will also flush the buffer immediately when the stream is being
+  /// set to unbuffered.
+  void SetUnbuffered(bool unbuffered) {
+    Unbuffered = unbuffered;
+    if (Unbuffered)
+      flush();
+  }
+
   //===--------------------------------------------------------------------===//
   // Data Output Interface
   //===--------------------------------------------------------------------===//
@@ -165,9 +177,11 @@ public:
   raw_fd_ostream(const char *Filename, bool Binary, std::string &ErrorInfo);
 
   /// raw_fd_ostream ctor - FD is the file descriptor that this writes to.  If
-  /// ShouldClose is true, this closes the file when
-  raw_fd_ostream(int fd, bool shouldClose) : FD(fd), ShouldClose(shouldClose) {}
-
+  /// ShouldClose is true, this closes the file when the stream is destroyed.
+  raw_fd_ostream(int fd, bool shouldClose, 
+                 bool unbuffered=false) : raw_ostream(unbuffered), FD(fd), 
+                                          ShouldClose(shouldClose) {}
+  
   ~raw_fd_ostream();
 
   /// flush_impl - The is the piece of the class that is implemented by

lib/Support/raw_ostream.cpp

@@ -141,6 +141,9 @@ raw_ostream &raw_ostream::write(const char *Ptr, unsigned Size) {
     break;
   }
   OutBufCur += Size;
+
+  if (Unbuffered)
+    flush_impl();
   return *this;
 }
 
@@ -266,7 +269,8 @@ uint64_t raw_fd_ostream::seek(uint64_t off) {
 //===----------------------------------------------------------------------===//
 
 raw_stdout_ostream::raw_stdout_ostream():raw_fd_ostream(STDOUT_FILENO, false) {}
-raw_stderr_ostream::raw_stderr_ostream():raw_fd_ostream(STDERR_FILENO, false) {}
+raw_stderr_ostream::raw_stderr_ostream():raw_fd_ostream(STDERR_FILENO, false, 
+                                                        true) {}
 
 // An out of line virtual method to provide a home for the class vtable.
 void raw_stdout_ostream::handle() {}