Fix a silly bug in StreamingMemoryObject.cpp.

The logic for detecting EOF was wrong and would fail if we ever requested
more than 16k past the last read position.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222505 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/StreamingMemoryObject.h

@@ -65,19 +65,20 @@ private:
   // Most of the requests will be small, but we fetch at kChunkSize bytes
   // at a time to avoid making too many potentially expensive GetBytes calls
   bool fetchToPos(size_t Pos) const {
-    if (EOFReached) return Pos < ObjectSize;
+    if (EOFReached)
+      return Pos < ObjectSize;
     while (Pos >= BytesRead) {
       Bytes.resize(BytesRead + BytesSkipped + kChunkSize);
       size_t bytes = Streamer->GetBytes(&Bytes[BytesRead + BytesSkipped],
                                         kChunkSize);
       BytesRead += bytes;
-      if (BytesRead <= Pos) { // reached EOF/ran out of bytes
+      if (bytes != kChunkSize) { // reached EOF/ran out of bytes
         ObjectSize = BytesRead;
         EOFReached = true;
-        return false;
+        break;
       }
     }
-    return true;
+    return Pos < BytesRead;
   }
 
   StreamingMemoryObject(const StreamingMemoryObject&) LLVM_DELETED_FUNCTION;

unittests/Support/CMakeLists.txt

@@ -32,6 +32,7 @@ add_llvm_unittest(SupportTests
   ScaledNumberTest.cpp
   SourceMgrTest.cpp
   SpecialCaseListTest.cpp
+  StreamingMemoryObject.cpp
   StringPool.cpp
   SwapByteOrderTest.cpp
   ThreadLocalTest.cpp

unittests/Support/StreamingMemoryObject.cpp

@@ -0,0 +1,30 @@
+//===- llvm/unittest/Support/StreamingMemoryObject.cpp - unit tests -------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/StreamingMemoryObject.h"
+#include "gtest/gtest.h"
+
+#include <string.h>
+
+using namespace llvm;
+
+namespace {
+class NullDataStreamer : public DataStreamer {
+  size_t GetBytes(unsigned char *buf, size_t len) override {
+    memset(buf, 0, len);
+    return len;
+  }
+};
+}
+
+TEST(StreamingMemoryObject, Test) {
+  auto *DS = new NullDataStreamer();
+  StreamingMemoryObject O(DS);
+  EXPECT_TRUE(O.isValidAddress(32 * 1024));
+}