gistfile1.cpp

#include <cstdint>
#include <iostream>
#include <unordered_map>

struct Foo
{
  int a;
};

uint64_t some_func();

int main( int argv, const char* argc[] )
{
  std::unordered_map<uint32_t, uint32_t> da_map;

  da_map.insert( std::make_pair( 123ULL, uint64_t(-1) ) );

  da_map.insert( std::make_pair( some_func(), some_func() ) );

  da_map.insert( std::pair<uint32_t, uint64_t>( some_func(), some_func() ) );

  std::unordered_map<uint32_t, uint32_t>::iterator iter1 = da_map.find( uint64_t(123ULL) );
  std::unordered_map<uint32_t, uint32_t>::iterator iter2 = da_map.find( uint64_t(-1) );
  std::unordered_map<uint32_t, uint32_t>::iterator iter3 = da_map.find( some_func() );

  std::cout << "sizeof<uint32_t>:" << sizeof(uint32_t) << "  sizeof<uint64_t>:" << sizeof(uint64_t) << std::endl;

  std::cout << "uint64_t(-1):" << uint64_t(-1) << "   map:" << da_map.find(uint64_t(-1))->first << std::endl;
}

/**
evan@om2:~$ clang++ -c umap.cc -std=c++0x -pedantic -Wconversion 
umap.cc:23:73: warning: implicit conversion from 'uint64_t' (aka 'unsigned long') to 'const key_type' (aka 'const unsigned int') changes value from 18446744073709551615 to 4294967295 [-Wconstant-conversion]
  std::unordered_map<uint32_t, uint32_t>::iterator iter2 = da_map.find( uint64_t(-1) );
                                                           ~~~~~~       ^~~~~~~~~~~~
umap.cc:24:73: warning: implicit conversion loses integer precision: 'uint64_t' (aka 'unsigned long') to 'const key_type' (aka 'const unsigned int') [-Wshorten-64-to-32]
  std::unordered_map<uint32_t, uint32_t>::iterator iter3 = da_map.find( some_func() );
                                                           ~~~~~~       ^~~~~~~~~~~
umap.cc:28:76: warning: implicit conversion from 'uint64_t' (aka 'unsigned long') to 'const key_type' (aka 'const unsigned int') changes value from 18446744073709551615 to 4294967295 [-Wconstant-conversion]
  std::cout << "uint64_t(-1):" << uint64_t(-1) << "   map:" << da_map.find(uint64_t(-1))->first << std::endl;
                                                               ~~~~~~      ^~~~~~~~~~~~

**/