lldb on xcode vs lldb on standalone

问题

I have this C++11 code that uses unique_ptr in vector.

#include <vector>
#include <iostream>
#include <memory>

using namespace std;

class A
{
    int x;
public:
    A() {}
    ~A() {}
    A(A& a) {}
    A(int x) {this->x = x;}
    int get() {return x;}
};

int main()
{
    vector<unique_ptr<A>> v;
    auto a = new A(10);
    unique_ptr<A> pa(a);
    v.push_back(move(pa)); // move(pa);

    auto a2 = new A(20);
    unique_ptr<A> pb(a2);
    v.push_back(move(pb)); // move(pa);

    for (auto& i: v)
    {
        cout << i->get();
    }
}

I could use Xcode to debug and check value in vector>. However, when I compile the same code with clang and debug in lldb, there are two errors.

The first one is lldb traces into STL source code.

* thread #1: tid = 0x1f03, 0x0000000100001744 a.out`__gnu_cxx::__normal_iterator<std::unique_ptr<A, std::default_delete<A> >*, std::vector<std::unique_ptr<A, std::default_delete<A> >, std::allocator<std::unique_ptr<A, std::default_delete<A> > > > >::operator*() const at stl_iterator.h:740, stop reason = step over
    frame #0: 0x0000000100001744 a.out`__gnu_cxx::__normal_iterator<std::unique_ptr<A, std::default_delete<A> >*, std::vector<std::unique_ptr<A, std::default_delete<A> >, std::allocator<std::unique_ptr<A, std::default_delete<A> > > > >::operator*() const at stl_iterator.h:740
   737  
   738        // Forward iterator requirements
   739        reference
-> 740        operator*() const
   741        { return *_M_current; }
   742  
   743        pointer
(lldb) n
Process 41243 stopped

The second error is I have segmentation error when I tried to see the vector contents.

(lldb) p v
Segmentation fault: 11

I used this command for compilation.

clang++ -std=c++11 -stdlib=libc++ -g testit.cpp -o a

What might be wrong?

回答1:

I reinstalled the Xcode with the newest version for Lion: Xcode 4.6, and the problem is gone.

回答2:

your segmentation fault seems like it could be caused by one of two things:

• the LLDB expression parser
• the LLDB data formatters

In order to tell which is which, the crash log will be necessary.

If you could retrieve it from ~/Library/Logs/DiagnosticReports and append it to this question (and also file a bug with Apple at http://bugreport.apple.com) it would be a good starting point

Also, it looks like you are using a pre-5 Xcode. Is that correct? Do you have access to the Xcode 5 Developer Preview to test if this reproduces? LLDB has been vastly improved between 4.x and 5, so you might have better luck.

来源：https://stackoverflow.com/questions/17256800/lldb-on-xcode-vs-lldb-on-standalone