formatted_raw_ostream: Fix a serious bug in tell().

- The current_pos function is supposed to return all the written bytes, not the
   current position of the underlying stream.
 - This caused tell() to be broken whenever the underlying stream had buffered
   content.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163948 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/FormattedStream.h

@@ -60,9 +60,10 @@ namespace llvm
     /// current_pos - Return the current position within the stream,
     /// not counting the bytes currently in the buffer.
     virtual uint64_t current_pos() const { 
-      // This has the same effect as calling TheStream.current_pos(),
-      // but that interface is private.
-      return TheStream->tell() - TheStream->GetNumBytesInBuffer();
+      // Our current position in the stream is all the contents which have been
+      // written to the underlying stream (*not* the current position of the
+      // underlying stream).
+      return TheStream->tell();
     }
 
     /// ComputeColumn - Examine the given output buffer and figure out which

unittests/Support/CMakeLists.txt

@@ -18,10 +18,11 @@ add_llvm_unittest(SupportTests
   ManagedStatic.cpp
   MathExtrasTest.cpp
   Path.cpp
-  raw_ostream_test.cpp
   RegexTest.cpp
   SwapByteOrderTest.cpp
   TimeValue.cpp
   ValueHandleTest.cpp
   YAMLParserTest.cpp
+  formatted_raw_ostream.cpp
+  raw_ostream_test.cpp
   )

unittests/Support/formatted_raw_ostream_test.cpp

@@ -0,0 +1,33 @@
+//===- llvm/unittest/Support/formatted_raw_ostream_test.cpp ---------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "gtest/gtest.h"
+#include "llvm/ADT/SmallString.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/FormattedStream.h"
+
+using namespace llvm;
+
+namespace {
+
+TEST(formatted_raw_ostreamTest, Test_Tell) {
+  // Check offset when underlying stream has buffer contents.
+  SmallString<128> A;
+  raw_svector_ostream B(A);
+  formatted_raw_ostream C(B);
+  char tmp[100] = "";
+
+  for (unsigned i = 0; i != 3; ++i) {
+    C.write(tmp, 100);
+
+    EXPECT_EQ(100*(i+1), (unsigned) C.tell());
+  }
+}
+
+}