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  1. #include <iostream>
  2. #include <memory>
  3. #include <vector>
  4.  
  5. struct Yoo
  6. {
  7.     Yoo(const char* s) : str(new std::string(s)) {}
  8.     ~Yoo() { delete str; str = nullptr; }
  9.     std::string* str;
  10. };
  11.  
  12. const size_t K = 1024;
  13. const size_t SZ = 16 * K;	// some big size
  14.  
  15. struct YooDeleter
  16. {
  17.     void operator()(Yoo* p) { delete p; }
  18.     char dummy[SZ];	// make the deleter big
  19. };
  20.  
  21. void bar()
  22. {
  23.     std::shared_ptr<Yoo> sp;
  24.  
  25.     Yoo* p = new Yoo("Hello");
  26.  
  27.     // try to exhaust heap memory.
  28.     std::vector<std::unique_ptr<YooDeleter>> holder;
  29.     holder.reserve(2048 * K); // 2M entries, big enough
  30.     for (;;)
  31.     {
  32.         try
  33.         {
  34.             std::unique_ptr<YooDeleter> p(new YooDeleter);
  35.             holder.push_back(std::move(p));
  36.         }
  37.         catch (...)
  38.         {
  39.             break;
  40.         }
  41.     }
  42.     std::cout << "Heap used: " << holder.size() << " x " << SZ / K << "KB" << std::endl;
  43.  
  44.     try
  45.     {
  46.     	YooDeleter x;
  47.         std::cout << "Creating shared_ptr..." << std::endl;
  48.     	sp = std::shared_ptr<Yoo>(p, x);
  49.     }
  50.     catch (std::bad_alloc& e)
  51.     {
  52.         // cannot construct sp: out of memory
  53.         std::cout << "Out of memory..." << std::endl;
  54.         std::cout << "I am about to crash..." << std::endl;
  55.         std::cout << p->str->c_str() << std::endl; // undefined behavior, mostly crash
  56.         delete p;   // will not even arriving here!
  57.         return;
  58.     }
  59.     catch(...)
  60.     {
  61.         std::cout << "Unknown error..." << std::endl;
  62.     	return;
  63.     }
  64.  
  65. 	// it will never be here!
  66.     *sp->str = "Bye";
  67.     std::cout << sp->str->c_str() << std::endl; // "Bye"
  68. }
  69.  
  70. int main()
  71. {
  72.     bar();
  73.     return 0;
  74. }
Runtime error #stdin #stdout 0.15s 1043456KB
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stdin
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Standard input is empty
stdout
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Heap used: 64457 x 16KB
Creating shared_ptr...
Out of memory...
I am about to crash...
https://ideone.com/bXN5Hp
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
public

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