ranged for-loop inside lambda crashes

[hessbe]

this example crashes the conversion:
void f() { auto lambda = [](auto container) { for(auto test : container) { } }; }

also with a template instantiation:
`#include
void f() {
auto lambda = [](auto container) {
for(auto test : container) { }
};

std::vector vec{1,2,3,4};
lambda(vec);
}`

[0x13449ff] ... [0x4055aa] Segmentation fault (core dumped)

[andreasfertig]

Hello @hessbe,

thank you! Nice finding. Here we have a range-based for-loop in an unevaluated context. Hence, not all the necessary information is present. My fix would be to show the range-based for-loop as it is in this cases. What do you think?

Andreas

[andreasfertig]

On a second thought, it is easier to transform it. This is more consistent and requires less special cases. Your initial example would then look like this:

void f()
{

  class __lambda_1_26
  {
    public:
    template<class type_parameter_0_0>
    inline /*constexpr */ auto operator()(type_parameter_0_0 container) const
    {
      {
        auto && __range1 = container;
        for(; ; )
        {
          auto test;
        }

      }
    }
    private:
    template<class type_parameter_0_0>
    static inline auto __invoke(type_parameter_0_0 container)
    {
      {
        auto && __range1 = container;
        for(; ; )
        {
          auto test;
        }

      }
    }

  };

  __lambda_1_26 lambda = __lambda_1_26{};
}

Andreas

[hessbe]

In my opinion that's good enough as long as the instantiation is correct.

Or how difficult is it to show everything with auto? Like this:
{ auto& __range1 = container; auto __begin1 = __range1.begin(); auto __end1 = __range1.end(); for(; __gnu_cxx::operator!=(__begin1, __end1); __begin1.operator++()) { auto test = __begin1.operator*(); // content of loop } }

[andreasfertig]

Hello @hessbe,

difficult as at this point it is unknown. It can also be that std::begin or std::end is called. Same goes for the operators. Plus it requires special treatment.
I prefer to transform what is there.

Andreas

[hessbe]

Hi Andrea,

I'm fully content with your proposed solution. I was preparing some examples for internal training and this crash popped up so I wanted to make sure you know about it. There was also a template instantiation In the example so the full solution would be shown there and that's all I wanted to show the team.

Ben

[andreasfertig]

Hello @hessbe,

excellent, and sorry for the trouble before your training. A fix is on its way.

Andreas