On Monday, 25 May 2020 at 00:56:04 UTC, Timon Gehr wrote:
[..]
After thinking about it, Walter ultimately made the right decision, leading to overall higher safety and code quality. We all agree that making extern C @safe is incorrect. It's also meaningless. Even if you were to verify the safety of a specific version of your binding, it can't be known what's loaded at runtime. It's not the compiler's concern. @safe extern shall be an error. We might additionally make an exception and make all extern C @system. It would be correct for the declarations, but inconsistent in regard to default safety. It doesn't affect the outcome. Let's say we'll go with @system, it gives us a bit more freedom. We hit compile, our now safe wrappers are errors. We are most likely to do one of two things, depending on the module failing to compile. If it mostly wrappers, we slap @trusted: at the top. If there are just a few functions calling C, we only annotate those with @trusted. Let's be real, we probably won't begin checking and annotating the trustworthiness of the C functions. An individual programmer might, but not on average. We are formally correct, but @trusted can't be trusted at this point. It has lost its meaning. We now have to check all foreign @trusted code, which we probably won't. We could have moved the problem one level down and slapped @trusted: on top of the @system declarations. Now there is a bunch of safe code using them. It doesn't change much. @trusted: is easier to grep, but we won't put everything down and begin trustworthily annotate extern C. So yeah, I do believe Walter was right. @safe on extern is formally incorrect but leads to safer code because @trusted still has its power.
