2013/5/15 Bryan Catanzaro <bcatanzaro@acm.org>:
Hi Antony - Perhaps it is compiler dependent. Which version of MSVC did you reproduce the error with? Does that version have c++11 support enabled (in particular, rvalue references) As I said, with Boost 1.48.0, this code works with g++ 4.6 and 4.7. With 1.53.0, it works with g++ 4.6 and 4.7 only if c++11 support is turned off. If c++11 support is turned on, the code does not work. I've attached a shell script that compiles the attached code with the cross product of {(g++4.6, g++4.7), (boost1.48, boost1.53), (noc++11, yesc++11)}. As you can see from test.txt, the error happens only with boost 1.53 and c++11 support.
- bryan
Exactly the same things happen on GCC-4.5 and Clang-3.0. But what is more interesting here: convertible c; const convertible& cc = c; // Always compiles, using any flags, compiler and Boost version my_variant y = cc; my_variant y1 = static_cast<const convertible&>(c); my_variant y2 = static_cast<const convertible>(c); // Always fail to compile, using any flags and Boost version // my_variant z = c; // my_variant y3 = static_cast<convertible&>(c); Tested on clang, gcc4.5, gcc 4.6, gcc4.7 on Boost 1.48 and Boost 1.53 with and without C++11 flags. If we modify `convertible`: struct convertible { operator my_variant() { return my_variant(); } operator my_variant() const { return my_variant(); } }; Then ALL the tests pass well, even the commented out ones. Even `my_variant y4 = static_cast<convertible&&>(c);` works well. I'll test it tomorrow on Visual Studio 11 once more and investigate issue futher. -- Best regards, Antony Polukhin