Issue with any_range and type erasure (in optimized code only)

[rolesen]

When a range is transformed into a new type and then "type erased" it gives an invalid range in optimized code only. See provided examples.

Using either the implicit conversion to any_range or the type erasure adaptor doesn't seem to make a difference.

Permalink to wandbox:

https://wandbox.org/permlink/CG2FhOBnO9gesp5w

#include <iostream>
#include <cstdlib>
#include <vector>
#include <boost/range.hpp>
#include <boost/range/adaptors.hpp>
#include <boost/range/adaptor/type_erased.hpp>

struct A {
  virtual void hello() {}
  int i = 0;
};

struct B : public A {
  double d = 0.0;
};

B* cast_to_B(A* a_ptr) {
    return static_cast<B*>(a_ptr);
}

double timesOneHalf(int in){
    return 1.5 * in;
}

void example_1() {//type transformation of int to double (including calculation)
    std::vector<int> vec{1, 2, 3};
    auto range = boost::make_iterator_range(vec.begin(), vec.end());
    auto range_transformed = range | boost::adaptors::transformed(timesOneHalf);

    boost::any_range<double, boost::iterators::bidirectional_traversal_tag> range_typeerased = range_transformed;//WARNING: function returns address of local variable

    std::cout << "transformed: " << *range_transformed.begin() << std::endl;
    std::cout << "type erased: " << *range_typeerased.begin() << std::endl;//seg fault or prints wrong value (should be 1.5) (when compiled with optimization)

    std::cout << "end of exampe 1" << std::endl;
}

void example_2() {//polymorphic type transformation example
    std::vector<A*> vec{new B, new B, new B};
    auto range = boost::make_iterator_range(vec.begin(), vec.end());
    auto range_transformed = range
    | boost::adaptors::transformed(cast_to_B);

    auto range_typeerased = range_transformed | boost::adaptors::type_erased<B*, boost::iterators::bidirectional_traversal_tag, B*, std::ptrdiff_t>();//WARNING: function returns address of local variable

    if (*range_transformed.begin() != *vec.begin()) {//OK (no type erasure involved yet)
      std::cout << "ASSERT 1: should have been the same" << std::endl;
    } 

    if (*range_typeerased.begin() != *vec.begin()) {//<--segmention fault or the assert fires (when compiled with optimization)
      std::cout << "ASSERT 2: should have been the same" << std::endl;
    }    

    std::cout << "end of exampe 2" << std::endl;
}

int main()
{
  example_1();
  example_2();

  std::cout << "Main finished!" << std::endl;
}

[rolesen]

I might add that it is also an issue when compiling with MSVC.

[mjendruk]

This issue was already posted 5 years ago in the Boost issue tracker: https://svn.boost.org/trac10/ticket/10493

I would also like to see this fixed.

Edit: The bug was probably introduced in: 79d2a66831af16f29befaa4d32461928b9431a15

[fdidoux]

IMHO the fix didn't fully solve the issue. At least, the code provided by rolesen still doesn't compile (even with gcc 11 and boost 1.76, which as far as I can see, contains the PR) - and same with Msvc 2019 (16.9.4)