Major changes:
- Define temporary scopes in a syntax-based way that basically defaults
to the innermost statement or conditional block, except for in
a `let` initializer, where we default to the innermost block. Rules
are documented in the code, but not in the manual (yet).
See new test run-pass/cleanup-value-scopes.rs for examples.
- Refactors Datum to better define cleanup roles.
- Refactor cleanup scopes to not be tied to basic blocks, permitting
us to have a very large number of scopes (one per AST node).
- Introduce nascent documentation in trans/doc.rs covering datums and
cleanup in a more comprehensive way.
Unique pointers and vectors currently contain a reference counting
header when containing a managed pointer.
This `{ ref_count, type_desc, prev, next }` header is not necessary and
not a sensible foundation for tracing. It adds needless complexity to
library code and is responsible for breakage in places where the branch
has been left out.
The `borrow_offset` field can now be removed from `TyDesc` along with
the associated handling in the compiler.
Closes#9510Closes#11533
Unique pointers and vectors currently contain a reference counting
header when containing a managed pointer.
This `{ ref_count, type_desc, prev, next }` header is not necessary and
not a sensible foundation for tracing. It adds needless complexity to
library code and is responsible for breakage in places where the branch
has been left out.
The `borrow_offset` field can now be removed from `TyDesc` along with
the associated handling in the compiler.
Closes#9510Closes#11533
When performing LTO, the rust compiler has an opportunity to completely strip
all landing pads in all dependent libraries. I've modified the LTO pass to
recognize the -Z no-landing-pads option when also running an LTO pass to flag
everything in LLVM as nothrow. I've verified that this prevents any and all
invoke instructions from being emitted.
I believe that this is one of our best options for moving forward with
accomodating use-cases where unwinding doesn't really make sense. This will
allow libraries to be built with landing pads by default but allow usage of them
in contexts where landing pads aren't necessary.
When performing LTO, the rust compiler has an opportunity to completely strip
all landing pads in all dependent libraries. I've modified the LTO pass to
recognize the -Z no-landing-pads option when also running an LTO pass to flag
everything in LLVM as nothrow. I've verified that this prevents any and all
invoke instructions from being emitted.
I believe that this is one of our best options for moving forward with
accomodating use-cases where unwinding doesn't really make sense. This will
allow libraries to be built with landing pads by default but allow usage of them
in contexts where landing pads aren't necessary.
cc #10780
This commit changes drop glue generated for structs to use the invoke LLVM
instruction instead of call. What this means is that if the user destructor
triggers an unwinding, then the fields of the struct will still ge dropped.
This is not an attempt to support failing while failing, as that's mostly a
problem of runtime support. This is more of an issue of soundness in making sure
that destructors are appropriately run. The test included fails before this
commit, and only has one call to fail!(), yet it doesn't destroy its struct
fields.
This is the culmination and attempted resolution of #8215. The commits have many more details about implementation details and the consequences of this refinement.
I'll point out specific locations which may be possible causes for alarm. In general, I have been very happy with how things have turned out. I'm a little sad that I couldn't remove privacy from resolve as much as I did, but I blame glob imports (although in theory even some of this can be mitigated as well).
This commit fixes all of the fallout of the previous commit which is an attempt
to refine privacy. There were a few unfortunate leaks which now must be plugged,
and the most horrible one is the current `shouldnt_be_public` module now inside
`std::rt`. I think that this either needs a slight reorganization of the
runtime, or otherwise it needs to just wait for the external users of these
modules to get replaced with their `rt` implementations.
Other fixes involve making things pub which should be pub, and otherwise
updating error messages that now reference privacy instead of referencing an
"unresolved name" (yay!).
