stacked_borrow now has an item module, and its own FrameExtra. These
serve to protect the implementation of Item (which is a bunch of
bit-packing tricks) from the primary logic of Stacked Borrows, and the
FrameExtra we have separates Stacked Borrows more cleanly from the
interpreter itself.
The new strategy for checking protectors also makes some subtle
performance tradeoffs, so they are now documented in Stack::item_popped
because that function primarily benefits from them, and it also touches
every aspect of them.
Also separating the actual CallId that is protecting a Tag from the Tag
makes it inconvienent to reproduce exactly the same protector errors, so
this also takes the opportunity to use some slightly cleaner English in
those errors. We need to make some change, might as well make it good.
Previously, Item was a struct of a NonZeroU64, an Option which was
usually unset or irrelevant, and a 4-variant enum. So collectively, the
size of an Item was 24 bytes, but only 8 bytes were used for the most
part.
So this takes advantage of the fact that it is probably impossible to
exhaust the total space of SbTags, and steals 3 bits from it to pack the
whole struct into a single u64. This bit-packing means that we reduce
peak memory usage when Miri goes memory-bound by ~3x. We also get CPU
performance improvements of varying size, because not only are we simply
accessing less memory, we can now compare a Vec<Item> using a memcmp
because it does not have any padding.
Extend `environ` linux extern implementation to freebsd
This fixes the `env` test on freebsd, and enables the CI test
Signed-off-by: InfRandomness <infrandomness@gmail.com>
Format tests with rustfmt (288-299 of 299)
Extracted from #2097.
I'll make a separate PR to enable checking the `tests` directory's formatting in CI. I'll need to rebase that after both this and #2254 have landed, and if any new non-rustfmt-formatted files appear in the meantime, we can include formatting those in the same PR that enables the CI.
Format tests with rustfmt (225-275 of 300)
Extracted from #2097.
These cases all involve a line comment at the end of a block that rustfmt has chosen to wrap.
```diff
- unsafe { (*ptr).set(20); } //~ ERROR does not exist in the borrow stack
+ unsafe {
+ (*ptr).set(20);
+ } //~ ERROR does not exist in the borrow stack
```
I have moved all of those comments back onto the same line as the content of the block instead, as was indicated being `@RalfJung's` preference in https://github.com/rust-lang/miri/pull/2097#discussion_r862436672.
```diff
+ unsafe {
+ (*ptr).set(20); //~ ERROR does not exist in the borrow stack
+ }
```
