Allow varargs for libc::open when it is allowed by the second argument
This PR allows `libc::open` to be called using two or three arguments as defined in https://man7.org/linux/man-pages/man2/open.2.html
The presence of the third argument depends on the value of the second argument. If the second argument dictates that the third argument is *required* miri will emit an error if the argument is missing. If the second argument does *not* require a third argument, then the argument is ignored and passed as 0 internally (it would be ignored by libc anyway)
add flag to forward specific env vars (while isolation remains enabled)
The flag is called `-Zmiri-env-forward=<var>`, but I am open to bikeshedding. ;)
exclude mutable references to !Unpin types from uniqueness guarantees
This basically works around https://github.com/rust-lang/unsafe-code-guidelines/issues/148 by not requiring uniqueness any more for mutable references to self-referential generators. That corresponds to [the same work-around that was applied in rustc itself](b815532674/compiler/rustc_middle/src/ty/layout.rs (L2482)).
I am not entirely sure if this is a good idea since it might hide too many errors in case types are "accidentally" `!Unpin`. OTOH, our test suite still passes, and to my knowledge the vast majority of types is `Unpin`. (`place.layout.ty` is monomorphic, we should always exactly know which type this is.)
intptrcast: Never allocate two objects directly adjecent
When two objects directly follow each other in memory, what is the
provenance of an integer cast to a pointer that points directly between
them? For a zero-size region, it could point into the end of the first
object, or the start of the second.
We can avoid answering this difficult question by simply never
allocating two objects directly beside each other. This fixes some of
the false positives from #1866.
When two objects directly follow each other in memory, what is the
provenance of an integer cast to a pointer that points directly between
them? For a zero-size region, it could point into the end of the first
object, or the start of the second.
We can avoid answering this difficult question by simply never
allocating two objects directly beside each other. This fixes some of
the false positives from #1866.
