Fixes for re-enabling more MSVC level 4 warnings: chrome/ edition

chrome/utility/media_galleries/pmp_column_reader_unittest.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <algorithm>
 #include <vector>
 
 #include "base/file_util.h"
 #include "base/files/file.h"
 #include "base/files/scoped_temp_dir.h"
@@ skipping 122 matching lines @@
       PmpTestUtil::MakeHeader(PMP_TYPE_STRING, 0);
   EXPECT_TRUE(InitColumnReaderFromBytes(&reader_good_header,
                                         good_header,
                                         PMP_TYPE_STRING));
   EXPECT_EQ(0U, reader_good_header.rows_read()) <<
       "Read non-zero rows from header-only data.";
 
   PmpColumnReader reader_bad_magic_bytes;
   std::vector<char> bad_magic_bytes =
       PmpTestUtil::MakeHeader(PMP_TYPE_STRING, 0);
-  bad_magic_bytes[0] = (char)0xff;
+  bad_magic_bytes[0] = static_cast<char>(-128);

[Peter Kasting, 2014/07/07 20:55:46]

0xff is considered by the compiler to be a positive value, and thus is larger
than what a signed char can hold, triggering a "constant truncated" warning.

To me, this suggests that this code should be using uint8_t, or at least
unsigned char, instead.  However, making that change turns out to be fairly
far-ranging (we have various routines in Chrome that use "vector<char>" to mean
"string of bytes"), so eventually I gave up and just made the change here.

   EXPECT_FALSE(InitColumnReaderFromBytes(&reader_bad_magic_bytes,
                                          bad_magic_bytes,
                                          PMP_TYPE_STRING));
 
   PmpColumnReader reader_inconsistent_types;
   std::vector<char> inconsistent_type =
       PmpTestUtil::MakeHeader(PMP_TYPE_STRING, 0);
-  inconsistent_type[kPmpFieldType1Offset] = (char)0xff;
+  inconsistent_type[kPmpFieldType1Offset] = static_cast<char>(-128);
   EXPECT_FALSE(InitColumnReaderFromBytes(&reader_inconsistent_types,
                                          inconsistent_type,
                                          PMP_TYPE_STRING));
 
   PmpColumnReader reader_invalid_type;
   std::vector<char> invalid_type =
       PmpTestUtil::MakeHeader(PMP_TYPE_STRING, 0);
-  invalid_type[kPmpFieldType1Offset] = (char)0xff;
-  invalid_type[kPmpFieldType2Offset] = (char)0xff;
+  invalid_type[kPmpFieldType1Offset] = static_cast<char>(-128);
+  invalid_type[kPmpFieldType2Offset] = static_cast<char>(-128);
   EXPECT_FALSE(InitColumnReaderFromBytes(&reader_invalid_type,
                                          invalid_type,
                                          PMP_TYPE_STRING));
 
   PmpColumnReader reader_incomplete_header;
   std::vector<char> incomplete_header =
       PmpTestUtil::MakeHeader(PMP_TYPE_STRING, 0);
   incomplete_header.resize(10);
   EXPECT_FALSE(InitColumnReaderFromBytes(&reader_incomplete_header,
                                          incomplete_header,
@@ skipping 25 matching lines @@
 TEST(PmpColumnReaderTest, PrimitiveParsing) {
   TestPrimitive<uint32>(PMP_TYPE_UINT32);
   TestPrimitive<double>(PMP_TYPE_DOUBLE64);
   TestPrimitive<uint8>(PMP_TYPE_UINT8);
   TestPrimitive<uint64>(PMP_TYPE_UINT64);
 }
 
 }  // namespace
 
 }  // namespace picasa