c++ initializer_list and shared_ptr behavior [dupl

问题:

This question already has an answer here:

• Double delete in initializer_list vs 2013 1 answer

I'm testing vs2013 c++ initializer_list.

The code below can be compiled. But crashes when i run exe.

#include <memory>
#include <iostream>

class Base {};

class Derived : public Base {};

void DoSomething(std::initializer_list<std::shared_ptr<Base> > list)
{
}

int main()
{
  auto ip = std::make_shared<Derived>();

  std::cout << "use_count=" << ip.use_count() << std::endl;

  DoSomething({ip, std::make_shared<Derived>()}); // ng
  // DoSomething({ip, std::make_shared<Base>()}); // ok
  // DoSomething({std::make_shared<Derived>(), ip}); // ok

  std::cout << "use_count=" << ip.use_count() << std::endl;
}

Compiles.

C:\...>cl.exe /EHsc test.cpp
Microsoft(R) C/C++ Optimizing Compiler Version 18.00.21005.1 for x86
Copyright (C) Microsoft Corporation.  All rights reserved.

test.cpp
Microsoft (R) Incremental Linker Version 12.00.21005.1
Copyright (C) Microsoft Corporation.  All rights reserved.

/out:test.exe
test.obj

C:\...>

I expected the output like this. g++4.8.2 works like this.

c:\...>test.exe
use_count=1
use_count=1

However, looks like this.

c:\...>test.exe
use_count=1
use_count=0 // or some random value like 3719232 and displayed crash dialog. 

And, Modifying one line of the code above, This works good.

DoSomething({std::make_shared<Derived>(), ip});

Is this a bug or normal behavior of vs2013 initializer_list ?

回答1:

Is this a bug or normal behavior of vs2013 initializer_list?

Yes to both. VS2013's std::initializer_list implementation is buggy; see similar questions Why first element is destroyed? and Double delete in initializer_list vs 2013.

Someone reported one of those issues to Microsoft in November 2013: http://connect.microsoft.com/VisualStudio/feedback/details/807419/initializer-lists-leaking-memory

This is now fixed in the Spring Update: Bugs Fixed in Visual Studio 2013 Update 2