ODR violations in boost::filesystem::path

[frankmiller]

There are a number of inline member functions in boost::filesystem::path that have different implementations depending on the definition of BOOST_FILESYSTEM_VERSION. When compiling boost.filesystem, BOOST_FILESYSTEM_VERSION is always set to 4. If a program uses boost.filesystem with BOOST_FILESYSTEM_VERSION set to 3, which is the default, then I believe this is an ODR violation because the program now has multiple definitions of the same function that do not consist of the same sequence of tokens.

[Lastique]

Duplicates #243.

Yes, this is formally an ODR violation. In practice, though, it works due to forced inlining of these methods. This will get resolved when v3 is dropped.

[frankmiller]

For the record, there is no inlining in a debug build. Also, I suspect LTO is interacting with inlining in unexpected ways, at least with msvc. I'm happy to resolve the issues I'm seeing on my end by moving to version 4. I just wanted to make sure the upstream maintainers were aware.

[Lastique]

Yes, debug build needs fixing.