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RAII and members if constructor throws?


By : shoucheng Duan
Date : July 30 2020, 12:00 AM
like below fixes the issue Yes, all completely-constructed members will be destroyed. Your object will not be left in any sort of "half-alive" state. No memory leaks will occur.
code :
#include <memory>
#include <iostream>

struct Bar
{
    Bar(const char* name, bool doThrow = false) : m_name(name)
    {
        if (doThrow)
        {
            std::cout << name << ": Bar() throwing\n";
            throw 0;
        }

        std::cout << name << ": Bar()\n";
    }

    ~Bar() { std::cout << m_name << ": ~Bar()\n"; }

private:
    const char* m_name;
};

class Foo {
  std::unique_ptr<Bar> x;
  std::unique_ptr<Bar> y;
 public:
  Foo(): x{new Bar("A")}, y{new Bar("B", true)} {}
};

int main()
{
    try
    {
        Foo f;
    }
    catch (...) {}
}

// g++ -std=c++17 -O2 -Wall -pedantic -pthread main.cpp && ./a.out
// A: Bar()
// B: Bar() throwing
// A: ~Bar()


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How can RAII be applied for class members that require extended initialization?


By : user3795487
Date : March 29 2020, 07:55 AM
seems to work fine Wrap the initialization code into a function, and use that function (member or non-member, static or non-static, as appropriate) to initialize the member variable:
code :
Texture Skybox::init_tex(std::string const& fileName) {
  // read stuff from file, including textureFile
  // initialize result
  return Texture(...);
}

Skybox::Skybox(std::string const& fileName):
  tex_(init_tex(fileName))
{ }

How does RAII work when a constructor throws an exception?


By : ali
Date : March 29 2020, 07:55 AM
hop of those help? You're misunderstanding the first quote. That's not hard, since it's confusing.
code :
class SomeType
{
  InnerType val;
public:
  SomeType() : val(...)
  {
    throw Exception;
  }
};

C++ using RAII with destructor that throws


By : Frank Verstappen
Date : March 29 2020, 07:55 AM
Does that help C++ will almost certainly have a function to obtain the current exception count as of C++1z (aka C++17 if they publish it on time!): std::uncaught_exceptions (note the plural "s"). Also, destructors are declared as noexcept by default (meaning that if you attempt to exit a destructor via an exception, std::terminate is called).
So, first, mark your destructor as throwing (noexcept(false)). Next, track the number of active exceptions in ctor, compare it to the value in dtor: if there are more uncaught exceptions in the dtor, you know that you are currently in the process of stack unwinding, and throwing again will result in a call to std::terminate.

What if RAII constructor throws?


By : vpul
Date : March 29 2020, 07:55 AM
I wish this helpful for you If the construction of mf fails, then the lifetime of mf will not be considered to have begun, any partial construction of mf will be reverted (by calling the destructors of bases and members that have completed their construction), and the following line, in which mf is used, will not be reached, since control will be transferred into a catch block (or the program will terminate).

RAII idiom for classes with container members


By : Markea Sheppard
Date : March 29 2020, 07:55 AM
wish of those help
Yes, every one of your objects is an RAII object, meaning that when it is destroyed it releases any and all acquired resources. Widget doesn't acquire any resources, so it has nothing to free. Similarly for Coord. Generally, standard library templates will be RAII as long as the template parameters are. So std::shared_ptr is an RAII object, as is std::map< std::tuple, std::shared_ptr>.
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