'hash_map' no se ha declarado en este ámbito con g ++ 4.2.1

Question

Estoy tratando de usar sgi hash_map.

#include <list> 
#include <iostream> 
#include <string> 
#include <map> 
#include <cstring> 
#include <tr1/unordered_map> 
#include <ext/hash_map> 


using namespace std; 
struct eqstr 
{ 
    bool operator()(const char* s1, const char* s2) const 
    { 
    return strcmp(s1, s2) == 0; 
    } 
}; 


int main() 
{ 
    hash_map<const char*, int, hash<const char*>, eqstr> months; 

    months["january"] = 31; 
    months["february"] = 28; 
    months["march"] = 31; 
    months["april"] = 30; 
    months["may"] = 31; 
    months["june"] = 30; 
    months["july"] = 31; 
    months["august"] = 31; 
    months["september"] = 30; 
    months["october"] = 31; 
    months["november"] = 30; 
    months["december"] = 31; 

    cout << "september -> " << months["september"] << endl; 
    cout << "april  -> " << months["april"] << endl; 
    cout << "june  -> " << months["june"] << endl; 
    cout << "november -> " << months["november"] << endl; 
} 

en gcc4.2 estoy recibiendo el error

listcheck.cc: In function 'int main()': 
listcheck.cc:22: error: 'hash_map' was not declared in this scope 
listcheck.cc:22: error: expected primary-expression before 'const' 
listcheck.cc:22: error: expected `;' before 'const' 
listcheck.cc:24: error: 'months' was not declared in this scope 

mientras que el mismo código compila con 3.4.

Answer 1

El archivo de inclusión <ext/hash_map> se refiere a la clase de mapa hash GNU extension y esto se declara en el espacio de nombres __gnu_cxx. O se puede calificar de forma explícita el nombre de la plantilla o añadir:

using namespace __gnu_cxx; 

Answer 2

Utilice <unordered_map>. hash_map era una extensión específica del proveedor, reemplazada por unordered_map.

Answer 3

usando __gnu_cxx espacio de nombres; eliminó el error de compilación.

usando

#include <hash_map> 

da esta advertencia y la eliminación da un error de compilación

In file included from /usr/include/c++/4.4/backward/hash_map:59, 
       from listcheck.cc:6: 
/usr/include/c++/4.4/backward/backward_warning.h:28:2: warning: #warning This file includes at least one deprecated or antiquated header which may be removed without further notice at a future date. Please use a non-deprecated interface with equivalent functionality instead. For a listing of replacement headers and interfaces, consult the file backward_warning.h. To disable this warning use -Wno-deprecated. 

después de retirar

#include <hash_map> 

g++ listcheck.cc 
listcheck.cc: In function ‘int main()’: 
listcheck.cc:20: error: ‘hash_map’ was not declared in this scope 
listcheck.cc:20: error: expected primary-expression before ‘const’ 
listcheck.cc:20: error: expected ‘;’ before ‘const’ 
listcheck.cc:21: error: ‘months’ was not declared in this scope