Change the behavior of the glue code emitted for `size_and_align_of_dst`.
This thus changes the behavior of `std::mem::size_of_val` and `std::mem::align_of_val`. It tries to move us towards a world where the following property holds:
Given type `T` implements `Trait` and a value `b: Box<T>`, where `std::mem::size_of::<T>()` returns `k`, then:
* `std::mem::size_of_val(b)` returns `k`
* `std::mem::size_of_val(b as Box<Trait>)` returns `k`
Note that one might legitimately question whether the above property *should* hold. The property certainly does not hold today, as illustrated by #27023.
(A follow-up task is to make various tests that check that the above property holds for a wide variety of types ... I chose not to invest effort in writing such a test before we actually determine that the above property is desirable.)
nmatsakis and pnkfelix agree that this PR does not require an RFC. cc @rust-lang/lang (since others may disagree).
(It also *might* break code, though it is hard for me to imagine that it could break code that wasn't already going to assert-fail when run in e.g. debug builds...)
Fix issue #27023
Also, this (or something like it) is a prerequisite for *fixing`make check` on `--enable-optimize --enable-debug` builds*
After #26694, the overloaded operator and "impl not known at method lookup time" cases started triggering the lint.
I've also added checks for overloaded autoderef and method calls via paths (i.e. `T::method()`).
All new 8 test cases did not trigger the lint before #26694.
r? @huonw
Closure variables represent the closure environment, not the closure
function, so the identifier used to ensure that the debuginfo is unique
for each kind of closure needs to be based on the closure upvars and not
the function signature.
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.
Updated all call sites that used the other contructors to uniformly
call `Lvalue::new_with_hint`, passing along the appropriate kind
of hint for each context.
Placated tidy in a few other places in datum.rs.
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.
(already thumbs-upped pre-rebase by nikomatsakis)
The refactoring here is trivial because `trans::datum::Lvalue`
currently carries no payload. However, future commits will start
adding a payload to `Lvalue`, and thus will force us either
1. to thread the payload through the `_match` code (a long term goal), or
2. to ensure the payload has some reasonable default value.
Closure variables represent the closure environment, not the closure
function, so the identifier used to ensure that the debuginfo is unique
for each kind of closure needs to be based on the closure upvars and not
the function signature.
TyClosure variant; thread this through wherever closure substitutions
are expected, which leads to a net simplification. Simplify trans
treatment of closures in particular.
Currently you can hit a link error on MSVC by only referencing static items from
a crate (no functions for example) and then link to the crate statically (as all
Rust crates do 99% of the time). A detailed investigation can be found [on
github][details], but the tl;dr is that we need to stop applying dllimport so
aggressively.
This commit alters the application of dllimport on constants to only cases where
the crate the constant originated from will be linked as a dylib in some output
crate type. That way if we're just linking rlibs (like the motivation for this
issue) we won't use dllimport. For the compiler, however, (which has lots of
dylibs) we'll use dllimport.
[details]: https://github.com/rust-lang/rust/issues/26591#issuecomment-123513631
cc #26591
When compiling libsyntax this removes about 30k basic blocks that only
contain a single unconditional jump and reduces the peak memory usage by
about 10MB (from 681MB down to 671MB).
The "hint" mechanism is essentially used as a workaround to compute
types for expressions which have not yet been type-checked. This
commit clarifies that usage, and limits the effects to the places
where it is currently necessary.
Fixes#26210.
This commit moves the IR files in the distribution, rust_try.ll,
rust_try_msvc_64.ll, and rust_try_msvc_32.ll into the compiler from the main
distribution. There's a few reasons for this change:
* LLVM changes its IR syntax from time to time, so it's very difficult to
have these files build across many LLVM versions simultaneously. We'll likely
want to retain this ability for quite some time into the future.
* The implementation of these files is closely tied to the compiler and runtime
itself, so it makes sense to fold it into a location which can do more
platform-specific checks for various implementation details (such as MSVC 32
vs 64-bit).
* This removes LLVM as a build-time dependency of the standard library. This may
end up becoming very useful if we move towards building the standard library
with Cargo.
In the immediate future, however, this commit should restore compatibility with
LLVM 3.5 and 3.6.
Currently you can hit a link error on MSVC by only referencing static items from
a crate (no functions for example) and then link to the crate statically (as all
Rust crates do 99% of the time). A detailed investigation can be found [on
github][details], but the tl;dr is that we need to stop applying dllimport so
aggressively.
This commit alters the application of dllimport on constants to only cases where
the crate the constant originated from will be linked as a dylib in some output
crate type. That way if we're just linking rlibs (like the motivation for this
issue) we won't use dllimport. For the compiler, however, (which has lots of
dylibs) we'll use dllimport.
[details]: https://github.com/rust-lang/rust/issues/26591#issuecomment-123513631
cc #26591
This commit moves the IR files in the distribution, rust_try.ll,
rust_try_msvc_64.ll, and rust_try_msvc_32.ll into the compiler from the main
distribution. There's a few reasons for this change:
* LLVM changes its IR syntax from time to time, so it's very difficult to
have these files build across many LLVM versions simultaneously. We'll likely
want to retain this ability for quite some time into the future.
* The implementation of these files is closely tied to the compiler and runtime
itself, so it makes sense to fold it into a location which can do more
platform-specific checks for various implementation details (such as MSVC 32
vs 64-bit).
* This removes LLVM as a build-time dependency of the standard library. This may
end up becoming very useful if we move towards building the standard library
with Cargo.
In the immediate future, however, this commit should restore compatibility with
LLVM 3.5 and 3.6.
Internally, the arguments passed to the closure are represented by a
tuple, but the actual function takes them as individual arguments, so we
have to untuple the arguments before creating the debuginfo.
We're currently using the actual function type as the return type when
creating the debug info for a function, so we're actually creating
debug info for a function that takes the same parameters, and returns
the actual function type, which is completely wrong.
The "hint" mechanism is essentially used as a workaround to compute
types for expressions which have not yet been type-checked. This
commit clarifies that usage, and limits the effects to the places
where it is currently necessary.
Fixes#26210.
Transition to the new object lifetime defaults, replacing the old defaults completely.
r? @pnkfelix
This is a [breaking-change] as specified by [RFC 1156][1156] (though all cases that would break should have been receiving warnings starting in Rust 1.2). Types like `&'a Box<Trait>` (or `&'a Rc<Trait>`, etc) will change from being interpreted as `&'a Box<Trait+'a>` to `&'a Box<Trait+'static>`. To restore the old behavior, write the `+'a` explicitly. For example, the function:
```rust
trait Trait { }
fn foo(x: &Box<Trait>) { ... }
```
would be rewritten as:
```rust
trait Trait { }
fn foo(x: &'a Box<Trait+'a>) { ... }
```
if one wanted to preserve the current typing.
[1156]: https://github.com/rust-lang/rfcs/blob/master/text/1156-adjust-default-object-bounds.md
Turns out for OSX our data layout was subtly wrong and the LLVM update must have
exposed this. Instead of fixing this I've removed all data layouts from the
compiler to just use the defaults that LLVM provides for all targets. All data
layouts (and a number of dead modules) are removed from the compiler here.
Custom target specifications can still provide a custom data layout, but it is
now an optional key as the default will be used if one isn't specified.
