On 11/06/2021 9:17 pm, Rainer Deyke wrote:
Actually, the standard library is a great example of what I am talking about. A header-only library (B) should not care about the specific implementation of the standard library (A) being used by the program (P). There is no link dependency from B to A. There is a requirement from B to P that P must provide /a/ implementation of the C++ standard library, but B doesn't care if it is libstdc++ or libc++ or even a custom standard library implementation that is part of P and not a separate library at all.
It does, however, need to be sure that it is using the same standard library as P (and with the same settings). Mixing multiple standard libraries into the same P will only end poorly -- which is usually also true (but less immediately obvious) when mixing multiple variants of other single libraries into P. You're assuming that by not specifying an explicit link from B to the standard library that it will inherently have the same settings as P. You're even mostly correct, because the standard library has a bit of special handling in the build tools. But this issue is not unique to the standard library, but applies to any dependency, including ones that you do have to explicitly tell the build tools about.