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

base/stringprintf_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 "base/basictypes.h"
 #include "base/stringprintf.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace base {
 
 namespace {
 
 // A helper for the StringAppendV test that follows.
 //
@@ skipping 150 matching lines @@
   SStringPrintf(&out, "%1$s %1$s", "test");
   EXPECT_STREQ("test test", out.c_str());
 
 #if defined(OS_WIN)
   std::wstring wout;
   SStringPrintf(&wout, L"%1$ls %1$ls", L"test");
   EXPECT_STREQ(L"test test", wout.c_str());
 #endif
 }
 
+// Test that StringPrintf and StringAppendV do not change errno.
+TEST(StringPrintfTest, StringPrintfErrno) {
+  errno = 1;
+  EXPECT_EQ("", StringPrintf("%s", ""));
+  EXPECT_EQ(1, errno);
+  std::string out;
+  StringAppendVTestHelper(&out, "%d foo %s", 1, "bar");
+  EXPECT_EQ(1, errno);
+}
+
 }  // namespace base