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  1. #include <iostream>
  2.  
  3. void register_callback(void* f, void* data);
  4. void invoke_callback();
  5.  
  6. template <typename T>
  7. void my_callback(void* data) {
  8.     T& x = *static_cast<T*>(data);
  9.     std:: cout << "Call[T] with " << x << std::endl;
  10. }
  11.  
  12. // Explicit instantiation:
  13. //template void my_callback<int>(void* data);
  14.  
  15. template <typename T>
  16. void do_register_callback(T& value) {
  17.     // Implicit instantiation:
  18.     if (false) { my_callback<T>(0); }
  19.     register_callback(reinterpret_cast<void*>(static_cast<void(*)(void*)>(my_callback<T>)), &value);
  20. }
  21.  
  22. int main() {
  23.     int ft = 42;
  24.     do_register_callback(ft);
  25.     invoke_callback();
  26. }
  27.  
  28. // [ Library ] /////////////////////////////////////////////////////////////////
  29.  
  30. struct callback_t {
  31.     void (*f)(void*);
  32.     void* data;
  33. } library_callback_data;
  34.  
  35. void register_callback(void* f, void* data) {
  36.     library_callback_data.f = reinterpret_cast<void(*)(void*)>(f);
  37.     library_callback_data.data = data;
  38. }
  39.  
  40. void invoke_callback() {
  41.     (*library_callback_data.f)(library_callback_data.data);
  42. }
Success #stdin #stdout 0s 2724KB
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Standard input is empty
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Call[T] with 42
https://ideone.com/3NNvM
language:
C++ (gcc 8.3)
created:
13 years ago
visibility:
public

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