Ask HN: Utility of a C multi-tls generic adapter lib?

Backends:

- OpenSSL and forks (LibreSSL, BoringSSL, s2n)

- mbedTLS (was PolarSSL)

- GUARD TLS Toolkit (was MatrixSSL)

- GnuTLS+Nettle

- Mesalink

- Network Security Services (NSS)

- WolfSSL

- Apple Security Framework

- Microsoft SChannel

Are any of the above (besides OpenSSL) obviously poorly-maintained, obsolete, buggy, fragile or unusable?

The initial concept would be compile-time backend switching so app maintainers only need to code against one interface for high-level operations while able to drop down into per-backend lib details, guarded by #ifdefs. Configuration would be pulled from the appropriate library.