As detailed in the Header dependency streamlining, originally found here, many of the standard C++ library include files have been edited to only include the smallest possible number of additional files. As such, many C++ programs that used std::memcpy without including <cstring>, or used std::auto_ptr without including <memory> will no longer compile.
If you receive: error: 'strcmp' was not declared in this scope
Fix it by including: #include <cstring> in the offending source file.
转自：http://rubypdf.diandian.com/post/2011-04-13/360263