Stop overwriting errno in base::StringPrintf, StringAppendV, and StringToDouble

base/strings/string_number_conversions_unittest.cc

 // Copyright (c) 2012 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 <errno.h>
 #include <math.h>
 
 #include <limits>
 
 #include "base/strings/string_number_conversions.h"
 #include "base/utf_string_conversions.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace base {
 
@@ skipping 427 matching lines @@
     {" 2.99", 2.99, false},
     {"1e3.4", 1000.0, false},
     {"nothing", 0.0, false},
     {"-", 0.0, false},
     {"+", 0.0, false},
     {"", 0.0, false},
   };
 
   for (size_t i = 0; i < ARRAYSIZE_UNSAFE(cases); ++i) {
     double output;
+    errno = 1;
     EXPECT_EQ(cases[i].success, StringToDouble(cases[i].input, &output));
+    if (cases[i].success)
+      EXPECT_EQ(1, errno) << i;  // confirm that errno is unchanged.
     EXPECT_DOUBLE_EQ(cases[i].output, output);
   }
 
   // One additional test to verify that conversion of numbers in strings with
   // embedded NUL characters.  The NUL and extra data after it should be
   // interpreted as junk after the number.
   const char input[] = "3.14\0159";
   std::string input_string(input, arraysize(input) - 1);
   double output;
   EXPECT_FALSE(StringToDouble(input_string, &output));
@@ skipping 32 matching lines @@
 
 TEST(StringNumberConversionsTest, HexEncode) {
   std::string hex(HexEncode(NULL, 0));
   EXPECT_EQ(hex.length(), 0U);
   unsigned char bytes[] = {0x01, 0xff, 0x02, 0xfe, 0x03, 0x80, 0x81};
   hex = HexEncode(bytes, sizeof(bytes));
   EXPECT_EQ(hex.compare("01FF02FE038081"), 0);
 }
 
 }  // namespace base