// C++N4606 Committee Draft, Standard for Programming Language C++
// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/n4606.pdf
#define msg "C++N460(274)30.6.8 Function template async [futures.async]p1393.cpp"
// Edited by Dr. Ogawa Kiyoshi. Compile procedure and results record.

#include <iostream>
#include <cstdlib>
#include <future>
#include <thread>
int work1(int value) {
  return value;
};
int work2(int value) {
  return value;
};
int work(int value) {
  auto handle = std::async([=] { return work2(value); });
  int tmp = work1(value);
  return tmp + handle.get(); // #1
}
int main()
{
  int i=3;
  std::cout<<"work("<<i<<")="<<work(i)<<std::endl;
  std::cout<< msg << std::endl;
  return EXIT_SUCCESS;
}

$ ./cppall.sh p1393
$ clang++ p1393.cpp -std=c++03 -Wall
p1393.cpp:13:1: warning: 'auto' type specifier is a C++11 extension
      [-Wc++11-extensions]
auto handle = std::async([=]{ return work2(value); });
^
p1393.cpp:13:26: error: expected expression
auto handle = std::async([=]{ return work2(value); });
                         ^
p1393.cpp:13:15: error: no member named 'async' in namespace 'std'; did you mean
      'std::launch::async'?
auto handle = std::async([=]{ return work2(value); });
              ^~~~~~~~~~
              std::launch::async
/usr/local/Cellar/llvm/6.0.0/include/c++/v1/future:404:5: note: 'std::launch::async'
      declared here
    async = 1,
    ^
1 warning and 2 errors generated.
$ clang++ p1393.cpp -std=c++11 -Wall
work(3)=6
C++N460(274)30.6.8 Function template async [futures.async]p1393.cpp
$ clang++ p1393.cpp -std=c++17 -Wall
work(3)=6
C++N460(274)30.6.8 Function template async [futures.async]p1393.cpp

$ g++-7 p1393.cpp -std=c++03  -Wall
In file included from /usr/local/Cellar/gcc/7.3.0_1/include/c++/7.3.0/future:35:0,
                 from p1393.cpp:8:
/usr/local/Cellar/gcc/7.3.0_1/include/c++/7.3.0/bits/c++0x_warning.h:32:2: error: #error This file requires compiler and library support for the ISO C++ 2011 standard. This support must be enabled with the -std=c++11 or -std=gnu++11 compiler options.
 #error This file requires compiler and library support \
  ^~~~~
p1393.cpp: In function 'int work(int)':
p1393.cpp:13:1: warning: 'auto' changes meaning in C++11; please remove it [-Wc++11-compat]
 auto handle = std::async([=]{ return work2(value); });
 ^~~~
p1393.cpp:13:6: error: 'handle' does not name a type; did you mean 'rand_r'?
 auto handle = std::async([=]{ return work2(value); });
      ^~~~~~
      rand_r
p1393.cpp:13:53: error: expected primary-expression before ')' token
 auto handle = std::async([=]{ return work2(value); });
                                                     ^
p1393.cpp:15:14: error: 'handle' was not declared in this scope
 return tmp + handle.get(); // #1
              ^~~~~~
p1393.cpp:15:14: note: suggested alternative: 'rand_r'
 return tmp + handle.get(); // #1
              ^~~~~~
              rand_r

$ g++-7 p1393.cpp -std=c++11  -Wall
work(3)=6
C++N460(274)30.6.8 Function template async [futures.async]p1393.cpp

$ g++-7 p1393.cpp -std=c++17  -Wall
work(3)=6
C++N460(274)30.6.8 Function template async [futures.async]p1393.cpp