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  1. #include <vector>
  2. class A {
  3.  public:
  4.   A() {}
  5. };
  6.  
  7. template<typename T>
  8. void foo(const T &p) {
  9.   union {
  10.     typename std::remove_const<
  11.       typename std::remove_reference<
  12.         decltype(p[0])
  13.       >::type
  14.     >::type
  15.     must_be_POD;
  16.  
  17.   } bar;
  18. } 
  19.  
  20. int main() {
  21.   int b[10];
  22.   A   c[10];
  23.   int *d = b;
  24.   A   *e = c;
  25.   foo(std::vector<int>(1)); // OK
  26.   foo(b);                   // OK
  27.   foo(d);                   // OK
  28.  // foo(std::vector<A>(1));   // ERROR
  29.  // foo(c);                   // ERROR
  30.  // foo(e);                   // ERROR
  31.   return 0;
  32. }
  33.  
Success #stdin #stdout 0s 3468KB
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https://ideone.com/HlBvDq
language:
C++14 (gcc 8.3)
created:
12 years ago
visibility:
public

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