How to fix "<hash_map> is deprecated and will be removed. Use <unordered_map>"?

Question

I am learning C ++, so I am working on the book "Programming: Principles and Practices Using C ++".

I'm in the first exercise, here's how to do "Hello, World!" using Microsoft Visual Studio 2015. I used the source code as stated in the book.

#include "../../std_lib_facilities.h" //header file recommended by book int main() //C++ programs start by executing the function main { cout <<"Hello, World!\n"; //output "Hello, World!" keep_window_open(); //wait for a character to be entered return 0; } 

However, when I try to create an executable program, I get two errors:

 IntelliSense: static assertion failed with "<hash_map> is deprecated and will be REMOVED. Please use <unordered_map>. You can define _SILENCE_STDEXT_HASH_DEPRECATION_WARNINGS to acknowledge that you have received this warning." Project: Hello, World! c:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\include\hash_map Line 14 Error C2338 <hash_map> is deprecated and will be REMOVED. Please use <unordered_map>. You can define _SILENCE_STDEXT_HASH_DEPRECATION_WARNINGS to acknowledge that you have received this warning. Project: Hello, World! c:\program files (x86)\microsoft visual studio 14.0\vc\include\hash_map Line 17 

Could you explain to me how I can fix this?

The code in std_lib_facilities.h is as follows:

 /* simple "Programming: Principles and Practice using C++" course header to be used for the first few weeks. It provides the most common standard headers (in the global namespace) and minimal exception/error support. Students: please don't try to understand the details of headers just yet. All will be explained. This header is primarily used so that you don't have to understand every concept all at once. Revised April 25, 2010: simple_error() added */ #ifndef H112 #define H112 201004L #include<iostream> #include<fstream> #include<sstream> #include<cmath> #include<cstdlib> #include<string> #include<list> #include<vector> #include<algorithm> #include<stdexcept> //--------------------------------------------------------------------------- --- #ifdef _MSC_VER #include <hash_map> using stdext::hash_map; #else #include <ext/hash_map> using __gnu_cxx::hash_map; namespace __gnu_cxx { template<> struct hash<std::string> { size_t operator()(const std::string& s) const { return hash<char*>()(s.c_str()); } }; } // of namespace __gnu_cxx #endif //--------------------------------------------------------------------------- --- #define unordered_map hash_map //--------------------------------------------------------------------------- --- typedef long Unicode; //--------------------------------------------------------------------------- --- using namespace std; template<class T> string to_string(const T& t) { ostringstream os; os << t; return os.str(); } struct Range_error : out_of_range { // enhanced vector range error reporting int index; Range_error(int i) :out_of_range("Range error: "+to_string(i)), index(i) { } }; // trivially range-checked vector (no iterator checking): template< class T> struct Vector : public std::vector<T> { typedef typename std::vector<T>::size_type size_type; Vector() { } explicit Vector(size_type n) :std::vector<T>(n) {} Vector(size_type n, const T& v) :std::vector<T>(n,v) {} template <class I> Vector(I first, I last) :std::vector<T>(first,last) {} T& operator[](unsigned int i) // rather than return at(i); { if (i<0||this->size()<=i) throw Range_error(i); return std::vector<T>::operator[](i); } const T& operator[](unsigned int i) const { if (i<0||this->size()<=i) throw Range_error(i); return std::vector<T>::operator[](i); } }; // disgusting macro hack to get a range checked vector: #define vector Vector // trivially range-checked string (no iterator checking): struct String : std::string { String() { } String(const char* p) :std::string(p) {} String(const string& s) :std::string(s) {} template<class S> String(S s) :std::string(s) {} String(int sz, char val) :std::string(sz,val) {} template<class Iter> String(Iter p1, Iter p2) : std::string(p1,p2) { } char& operator[](unsigned int i) // rather than return at(i); { if (i<0||size()<=i) throw Range_error(i); return std::string::operator[](i); } const char& operator[](unsigned int i) const { if (i<0||size()<=i) throw Range_error(i); return std::string::operator[](i); } }; #ifndef _MSC_VER namespace __gnu_cxx { template<> struct hash<String> { size_t operator()(const String& s) const { return hash<std::string>()(s); } }; } // of namespace __gnu_cxx #endif struct Exit : runtime_error { Exit(): runtime_error("Exit") {} }; // error() simply disguises throws: inline void error(const string& s) { throw runtime_error(s); } inline void error(const string& s, const string& s2) { error(s+s2); } inline void error(const string& s, int i) { ostringstream os; os << s <<": " << i; error(os.str()); } #if _MSC_VER<1500 // disgusting macro hack to get a range checked string: #define string String // MS C++ 9.0 have a built-in assert for string range check // and uses "std::string" in several places so that macro substitution fails #endif template<class T> char* as_bytes(T& i) // needed for binary I/O { void* addr = &i; // get the address of the first byte // of memory used to store the object return static_cast<char*>(addr); // treat that memory as bytes } inline void keep_window_open() { cin.clear(); cout << "Please enter a character to exit\n"; char ch; cin >> ch; return; } inline void keep_window_open(string s) { if (s=="") return; cin.clear(); cin.ignore(120,'\n'); for (;;) { cout << "Please enter " << s << " to exit\n"; string ss; while (cin >> ss && ss!=s) cout << "Please enter " << s << " to exit\n"; return; } } // error function to be used (only) until error() is introduced in Chapter 5: inline void simple_error(string s) // write ``error: s?? and exit program { cerr << "error: " << s << '\n'; keep_window_open(); // for some Windows environments exit(1); } // make std::min() and std::max() accessible: #undef min #undef max #include<iomanip> inline ios_base& general(ios_base& b) // to augment fixed and scientific { b.setf(ios_base::fmtflags(0),ios_base::floatfield); return b; } // run-time checked narrowing cast (type conversion): template<class R, class A> R narrow_cast(const A& a) { R r = R(a); if (A(r)!=a) error(string("info loss")); return r; } inline int randint(int max) { return rand()%max; } inline int randint(int min, int max) { return randint(max-min)+min; } inline double sqrt(int x) { return sqrt(double(x)); } // to match C++0x #endif 

Answer 1

There are several ways to fix this. You could simply ignore the compiler in visual studio by writing

#define _SILENCE_STDEXT_HASH_DEPRECATION_WARNINGS 1

at the top of its header file (and you'll probably be fine for the rest of its series).

You can also rewrite your header instead of hash_map using unordered_map . I do not recommend this, since you are new to programming, but some soul in Qaru can do this for you, and you can copy it (it should not be difficult). EDIT: TC found here in the comments section of your post.

Finally, you can simply include the necessary header files for what you are doing in the book, and manually record any functions that it uses as needed. In this case, to access the cout function, you need to write #include <iostream> at the top of your file, and then also write using namespace std; before your int main() . Alternatively, you can write std::cout << "Hello World!"; without inclusion using namespace std; to make it all happen. The final product will look like this:

 #include <iostream> //for learning, it probably better to know what each header file does before you use it. silly book. using namespace std; //act like std:: is before function calls from that library int main() //C++ programs start by executing the function main { cout <<"Hello, World!\n"; //output "Hello, World!" cin.get(); //wait for a return character to be entered return 0; } 

After seeing how you send to Qaru for starters and probably have a high ability to learn C ++, I recommend doing the latter and trying to see exactly what its functions do when you get into his book, and then doing a quick Internet search for any interesting things you want to learn.

Answer 2

I think the best solution for a specific OP problem is to download an updated version of std_lib_facilities.h here . The new file uses unordered_map instead of hash_map .

Note. This solution has already been proposed by TC in the comments, and is also mentioned somewhere in TheSmartWon's answer. I wrote a new answer only because it’s easier for other users to find this information.