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Avoid creating references to out params #256

Closed jsha closed 2 years ago

jsha commented 2 years ago

Creating a reference to uninitialized memory is undefined behavior. Callers of this library are likely to pass pointers to uninitialized memory as out params. We should support that by not turning out params into references.

Instead, keep them as raw pointers and use an unsafe block where we actually write the param.

Fixes #245

jsha commented 2 years ago

@tgeoghegan @djc if either of you is available to review this, I'd appreciate it. Thanks!

jsha commented 2 years ago

I updated the issue with some related links: https://github.com/rustls/rustls-ffi/issues/245#issuecomment-1101712972. In particular, Miri can't catch this problem. From the Miri README:

In particular, Miri does currently not check that integers/floats are initialized or that references point to valid data.

djc commented 2 years ago

This looks reasonable to me (though I haven't reviewed the unsafe invariants in depth).