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

base/scoped_clear_errno.h

Index: base/scoped_clear_errno.h
diff --git a/base/scoped_clear_errno.h b/base/scoped_clear_errno.h
new file mode 100644
index 0000000000000000000000000000000000000000..7b972fc85ac6fc4b7a1f1d721df0cebd53ca2120
--- /dev/null
+++ b/base/scoped_clear_errno.h
@@ -0,0 +1,34 @@
+// Copyright (c) 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.
+
+#ifndef BASE_SCOPED_CLEAR_ERRNO_H_
+#define BASE_SCOPED_CLEAR_ERRNO_H_
+
+#include <errno.h>
+
+#include "base/basictypes.h"
+
+namespace base {
+
+// Simple scoper that saves the current value of errno, resets it to 0, and on
+// destruction puts the old value back.
+class ScopedClearErrno {
+ public:
+  ScopedClearErrno() : old_errno_(errno) {
+    errno = 0;
+  }
+  ~ScopedClearErrno() {
+    if (errno == 0)
+      errno = old_errno_;
+  }
+
+ private:
+  const int old_errno_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedClearErrno);
+};
+
+}  // namespace base
+
+#endif  // BASE_SCOPED_CLEAR_ERRNO_H_