[pornel]

If you've chosen to use an ancient OS, with an obsolete compiler, you should not expect to be able to use anything new with it. Just keep the mothballed code as-is. Maybe find an equally old version of the library B if you must.

Or pay RedHat to backport the library B to the old Boost for you :)

[TillE]

Also you can almost certainly use a newer compiler to target old OSes.

The real problem is when you have a big pile of ancient, unmaintained code that uses long-deprecated stuff. At that point, no, you really can't expect to seamlessly interoperate with new code.