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  1. #include <iostream>
  2. #include <iomanip>
  3. #include <cstdlib>
  4. #include <cstring>
  5.  
  6. int dump(void *s, size_t size) {
  7.     unsigned char *buf = (unsigned char*)s;
  8.     for (size_t i=0; i<size; ++i) {
  9.         std::cout << std::hex << std::setw(2) << std::setfill('0') << (int)buf[i] << " ";
  10.     }
  11.     std::cout << std::endl;
  12.     return 5;
  13. }
  14.  
  15. struct Test {
  16.     Test() : x(dump(this, sizeof(*this))) {
  17.         std::cout << "In c'tor:            ";
  18.         dump(this, sizeof(*this));
  19.         memset(this, 0, sizeof(*this));
  20.     }
  21.     virtual ~Test() {
  22.     }
  23.     int x;
  24. };
  25.  
  26. struct T : Test
  27. {};
  28.  
  29. int main() {
  30.     T *t = (T*)calloc(1, sizeof(T));
  31.     std::cout << "Before construction: ";
  32.     dump(t, sizeof(Test));
  33.     new(t) T;
  34.     std::cout << "After construction:  ";
  35.     dump(t, sizeof(Test));
  36.     return 0;
  37. }
Success #stdin #stdout 0.02s 2856KB
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stdin
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Standard input is empty
stdout
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Before construction: 00 00 00 00 00 00 00 00 
c0 8d 04 08 00 00 00 00 
In c'tor:            c0 8d 04 08 05 00 00 00 
After construction:  90 8d 04 08 00 00 00 00
https://ideone.com/zuoO3y
language:
C++ (gcc 8.3)
created:
13 years ago
visibility:
public

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