These commits perform a few high-level changes with the goal of enabling i686 MSVC unwinding:
* LLVM is upgraded to pick up the new exception handling instructions and intrinsics for MSVC. This puts us somewhere along the 3.8 branch, but we should still be compatible with LLVM 3.7 for non-MSVC targets.
* All unwinding for MSVC targets (both 32 and 64-bit) are implemented in terms of this new LLVM support. I would like to also extend this to Windows GNU targets to drop the runtime dependencies we have on MinGW, but I'd like to land this first.
* Some tests were fixed up for i686 MSVC here and there where necessary. The full test suite should be passing now for that target.
In terms of landing this I plan to have this go through first, then verify that i686 MSVC works, then I'll enable `make check` on the bots for that target instead of just `make` as-is today.
Closes#25869
This brings some routine upgrades to the bundled LLVM that we're using, the most
notable of which is a bug fix to the way we handle range asserts when loading
the discriminant of an enum. This fix ended up being very similar to f9d4149c
where we basically can't have a range assert when loading a discriminant due to
filling drop, and appropriate flags were added to communicate this to
`trans::adt`.
When cross compiling for a target that has a larger usize type than the
host system, we use a truncated value to mark data as dropped,
eventually leading to drop calls on already dropped data. To properly
handle this, the drop pattern needs to be of type u64.
Since C_integral truncates its given value to the requested size anyway,
we can also drop the function that chose between the u32 and u64 values,
and always use the u64 constant.
Fixes#31139
In particular, bring back the `zero` flag for `lvalue_scratch_datum`,
which controls whether the alloca's created immediately at function
start are uninitialized at that point or have their embedded
drop-flags initialized to "dropped".
Then made `to_lvalue_datum_in_scope` pass "dropped" as `zero` flag.
The presence of the drop flag caused the offset calculation to be
incorrect, leading to the pointer being incorrect. This has been fixed
by calculating the offset based on the field index (and not assuming
that the field is always the last one).
However, I've also stopped the drop flag from being added to the end of
unsized structs to begin with. Since it's not actually accessed for
unsized structs, and isn't actually where we would say it is, this made
more sense.
DST fields, being of an unknown type, are not automatically aligned
properly, so a pointer to the field needs to be aligned using the
information in the vtable.
Fixes#26403 and a number of other DST-related bugs discovered while
implementing this.
This commit is the standard API stabilization commit for the 1.6 release cycle.
The list of issues and APIs below have all been through their cycle-long FCP and
the libs team decisions are listed below
Stabilized APIs
* `Read::read_exact`
* `ErrorKind::UnexpectedEof` (renamed from `UnexpectedEOF`)
* libcore -- this was a bit of a nuanced stabilization, the crate itself is now
marked as `#[stable]` and the methods appearing via traits for primitives like
`char` and `str` are now also marked as stable. Note that the extension traits
themeselves are marked as unstable as they're imported via the prelude. The
`try!` macro was also moved from the standard library into libcore to have the
same interface. Otherwise the functions all have copied stability from the
standard library now.
* The `#![no_std]` attribute
* `fs::DirBuilder`
* `fs::DirBuilder::new`
* `fs::DirBuilder::recursive`
* `fs::DirBuilder::create`
* `os::unix::fs::DirBuilderExt`
* `os::unix::fs::DirBuilderExt::mode`
* `vec::Drain`
* `vec::Vec::drain`
* `string::Drain`
* `string::String::drain`
* `vec_deque::Drain`
* `vec_deque::VecDeque::drain`
* `collections::hash_map::Drain`
* `collections::hash_map::HashMap::drain`
* `collections::hash_set::Drain`
* `collections::hash_set::HashSet::drain`
* `collections::binary_heap::Drain`
* `collections::binary_heap::BinaryHeap::drain`
* `Vec::extend_from_slice` (renamed from `push_all`)
* `Mutex::get_mut`
* `Mutex::into_inner`
* `RwLock::get_mut`
* `RwLock::into_inner`
* `Iterator::min_by_key` (renamed from `min_by`)
* `Iterator::max_by_key` (renamed from `max_by`)
Deprecated APIs
* `ErrorKind::UnexpectedEOF` (renamed to `UnexpectedEof`)
* `OsString::from_bytes`
* `OsStr::to_cstring`
* `OsStr::to_bytes`
* `fs::walk_dir` and `fs::WalkDir`
* `path::Components::peek`
* `slice::bytes::MutableByteVector`
* `slice::bytes::copy_memory`
* `Vec::push_all` (renamed to `extend_from_slice`)
* `Duration::span`
* `IpAddr`
* `SocketAddr::ip`
* `Read::tee`
* `io::Tee`
* `Write::broadcast`
* `io::Broadcast`
* `Iterator::min_by` (renamed to `min_by_key`)
* `Iterator::max_by` (renamed to `max_by_key`)
* `net::lookup_addr`
New APIs (still unstable)
* `<[T]>::sort_by_key` (added to mirror `min_by_key`)
Closes#27585Closes#27704Closes#27707Closes#27710Closes#27711Closes#27727Closes#27740Closes#27744Closes#27799Closes#27801
cc #27801 (doesn't close as `Chars` is still unstable)
Closes#28968
This is trickier than it sounds (because the DST code was written
assuming that one could divide the sized and unsized portions of a
type strictly into a sized prefix and unsized suffix, when it reality
it is more like a sized prefix and sized suffix that surround the
single unsized field).
I chose to put in a pretty hack-ish approach to this because
drop-flags are scheduled to go away anyway, so its not really worth
the effort to to make an infrastructure that sounds as general as the
previous paragraph indicates.
Also, I have written notes of other fixes that need to be made to
really finish fixing #27023, namely more work needs to be done to
account for alignment when computing the size of a value.
Added code to maintain these hints at runtime, and to conditionalize
drop-filling and calls to destructors.
In this early stage, we are using hints, so we are always free to
leave out a flag for a path -- then we just pass `None` as the
dropflag hint in the corresponding schedule cleanup call. But, once a
path has a hint, we must at least maintain it: i.e. if the hint
exists, we must ensure it is never set to "moved" if the data in
question might actually have been initialized. It remains sound to
conservatively set the hint to "initialized" as long as the true
drop-flag embedded in the value itself is up-to-date.
----
Here are some high-level details I want to point out:
* We maintain the hint in Lvalue::post_store, marking the lvalue as
moved. (But also continue drop-filling if necessary.)
* We update the hint on ExprAssign.
* We pass along the hint in once closures that capture-by-move.
* You only call `drop_ty` for state that does not have an associated hint.
If you have a hint, you must call `drop_ty_core` instead.
(Originally I passed the hint into `drop_ty` as well, to make the
connection to a hint more apparent, but the vast majority of
current calls to `drop_ty` are in contexts where no hint is
available, so it just seemed like noise in the resulting diff.)
Instrumented calls sites that construct Lvalues to ease tracking down
cases that we might need to change whether or not they carry a hint.
Note that this commit does not do anything to actually *construct*
the `lldropflag_hints` map, nor does it change anything about codegen
itself. Those parts are in follow-on commits.
TyClosure variant; thread this through wherever closure substitutions
are expected, which leads to a net simplification. Simplify trans
treatment of closures in particular.
This commit finalizes the work of the past commits by fully moving the fulfillment context into
the InferCtxt, cleaning up related context interfaces, removing the Typer and ClosureTyper
traits and cleaning up related intefaces
This commit updates the LLVM submodule in use to the current HEAD of the LLVM
repository. This is primarily being done to start picking up unwinding support
for MSVC, which is currently unimplemented in the revision of LLVM we are using.
Along the way a few changes had to be made:
* As usual, lots of C++ debuginfo bindings in LLVM changed, so there were some
significant changes to our RustWrapper.cpp
* As usual, some pass management changed in LLVM, so clang was re-scrutinized to
ensure that we're doing the same thing as clang.
* Some optimization options are now passed directly into the
`PassManagerBuilder` instead of through CLI switches to LLVM.
* The `NoFramePointerElim` option was removed from LLVM, favoring instead the
`no-frame-pointer-elim` function attribute instead.
* The `LoopVectorize` option of the LLVM optimization passes has been disabled
as it causes a divide-by-zero exception to happen in LLVM for zero-sized
types. This is reported as https://llvm.org/bugs/show_bug.cgi?id=23763
Additionally, LLVM has picked up some new optimizations which required fixing an
existing soundness hole in the IR we generate. It appears that the current LLVM
we use does not expose this hole. When an enum is moved, the previous slot in
memory is overwritten with a bit pattern corresponding to "dropped". When the
drop glue for this slot is run, however, the switch on the discriminant can
often start executing the `unreachable` block of the switch due to the
discriminant now being outside the normal range. This was patched over locally
for now by having the `unreachable` block just change to a `ret void`.
This commit updates the LLVM submodule in use to the current HEAD of the LLVM
repository. This is primarily being done to start picking up unwinding support
for MSVC, which is currently unimplemented in the revision of LLVM we are using.
Along the way a few changes had to be made:
* As usual, lots of C++ debuginfo bindings in LLVM changed, so there were some
significant changes to our RustWrapper.cpp
* As usual, some pass management changed in LLVM, so clang was re-scrutinized to
ensure that we're doing the same thing as clang.
* Some optimization options are now passed directly into the
`PassManagerBuilder` instead of through CLI switches to LLVM.
* The `NoFramePointerElim` option was removed from LLVM, favoring instead the
`no-frame-pointer-elim` function attribute instead.
Additionally, LLVM has picked up some new optimizations which required fixing an
existing soundness hole in the IR we generate. It appears that the current LLVM
we use does not expose this hole. When an enum is moved, the previous slot in
memory is overwritten with a bit pattern corresponding to "dropped". When the
drop glue for this slot is run, however, the switch on the discriminant can
often start executing the `unreachable` block of the switch due to the
discriminant now being outside the normal range. This was patched over locally
for now by having the `unreachable` block just change to a `ret void`.
* segfault due to not copying drop flag when coercing
* fat pointer casts
* segfault due to not checking drop flag properly
* debuginfo for DST smart pointers
* unreachable code in drop glue
Inspect enum discriminant *after* calling its destructor
Includes some drive-by cleanup (e.g. changed some field and method names to reflect fill-on-drop; added comments about zero-variant enums being classified as `_match::Single`).
Probably the most invasive change was the expansion of the maps `available_drop_glues` and `drop_glues` to now hold two different kinds of drop glues; there is the (old) normal drop glue, and there is (new) drop-contents glue that jumps straight to dropping the contents of a struct or enum, skipping its destructor.
* For all types that do not have user-defined Drop implementations, the normal glue is generated as usual (i.e. recursively dropping the fields of the data structure).
(And this actually is exactly what the newly-added drop-contents glue does as well.)
* For types that have user-defined Drop implementations, the "normal" drop glue now schedules a cleanup before invoking the `Drop::drop` method that will call the drop-contents glue after that invocation returns.
Fix#23611.
----
Is this a breaking change? The prior behavior was totally unsound, and it seems unreasonable that anyone was actually relying on it.
Nonetheless, since there is a user-visible change to the language semantics, I guess I will conservatively mark this as a:
[breaking-change]
(To see an example of what sort of user-visible change this causes, see the comments in the regression test.)
Kudos to dotdash for tracking down this fix.
Presumably the use of `ByRef` was because this value is a reference to
the drop-flag; but an Lvalue will serve just as well for that. dotdash
argues:
> since the drop_flag is in its "final home", Lvalue seems to be the
> correct choice.
