I wonder if Solaris ABI compat is actually older than the Windows stuff. Solaris to this day maintains binary compat with older releases and, for example, a 32-bit fopen() will fail once you open 255 streams because that was the limit in the ancient ABI. Everyone using Solaris at one point or another has probably hit this and it caused some issue, but Sun^H^H^HOracle refuses to make modern operation the default, all in the name of ancient binary compat. That's a bit more hardcore than optional support you can enable.