lexical_cast: invalid application of 'sizeof' to incomplete type 'removed_ptr_t'

[pmachata@…]

This is triggered by use of incomplete types, as in the following code:

#include <boost/lexical_cast.hpp>
#include <iostream>
struct ble;
typedef struct ble *meh;
std::ostream &
operator <<(std::ostream &o, meh m) {
  o << "yay";
}
int main(int argc, char *argv[]) {
  meh heh;
  std::cout << boost::lexical_cast<std::string>(heh) << std::endl;
}

This used to work as expected with boost 1.46.1. With boost 1.48.0, the compilation fails with the following message:

In file included from x.cc:1:0:
/usr/include/boost/lexical_cast.hpp: In static member function 'static Target boost::detail::lexical_cast_do_cast<Target, Source>::lexical_cast_impl(const Source&) [with Target = std::basic_string<char>, Source = ble*]':
/usr/include/boost/lexical_cast.hpp:1916:50:   instantiated from 'Target boost::lexical_cast(const Source&) [with Target = std::basic_string<char>, Source = ble*]'
x.cc:16:52:   instantiated from here
/usr/include/boost/lexical_cast.hpp:1742:25: error: invalid application of 'sizeof' to incomplete type 'removed_ptr_t {aka ble}' 

The compiler used is GCC 4.6.1, and I imagine that others would be impacted, too.

[pmachata@…]

Proposed fix

[anonymous]

About the proposed fix. To decide whether source type is char, you first ask whether it's char or wchar, and then compare sizeofs. I think the same can be achieved by simply asking whether src is char. I might be missing something though. That's what the patch implements.

[anonymous]

The bug is also present in svn trunk.

[Antony Polukhin]

Replying to anonymous:

About the proposed fix. To decide whether source type is char, you first ask whether it's char or wchar, and then compare sizeofs. I think the same can be achieved by simply asking whether src is char. I might be missing something though. That's what the patch implements.

The problem here, is that we have char, unsigned char, signed char, wchar_t, char16_t and char32_t types (not only char). And we still need to construct stringbuffer for char types with different sizes.

Great thanks for bug report and for giving ideas for it fixing.

[Antony Polukhin]

(In [76305]) Fixes #6132 Fixes #6182