... through yields
This avoids the following pathological scenario that makes threadring OOM:
1) task calls C using fast_ffi, borrowing a big stack from the scheduler.
2) task returns from C and places the big stack on the task-local stack segment list
3) task calls further Rust functions that require growing the stack, and for this reuses the big stack
4) task yields, failing to return the big stack to the scheduler.
5) repeat 500+ times and OOM
(reopening after incoming fallout. *do not r+*. broken)
This avoids the following pathological scenario that makes threadring OOM:
1) task calls C using fast_ffi, borrowing a big stack from the scheduler.
2) task returns from C and places the big stack on the task-local stack segment list
3) task calls further Rust functions that require growing the stack, and for this reuses the big stack
4) task yields, failing to return the big stack to the scheduler.
5) repeat 500+ times and OOM
Conflicts:
src/rt/rust_task.cpp
Fix#7322.
I started out with a band-aid approach to special-case the duplicate module error using `is_duplicate_module`, but thought this would be better in the long term.
add_child() is responsible for reporting errors about type, value, and
module duplicate definitions. Although it checks for all three, it uses
namespace_to_str() to convert a Namespace value into a string before
printing an error like:
error: duplicate definition of type `foo`
^^^^
note: first definition of type foo here:
^^^^
Unfortunately, this string can only be one of "type" or
"value" (corresponding to TypeNS and ValueNS respectively), and it
reports duplicate modules as duplicate types.
To alleviate the problem, define a special NamespaceError enum to define
more specialized errors, and use it instead of attempting to reuse the
Namespace enum.
Reported-by: Corey Richardson <corey@octayn.net>
Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
This adds a `#[no_drop_flag]` attribute. This attribute tells the compiler to omit the drop flag from the struct, if it has a destructor. When the destructor is run, instead of setting the drop flag, it instead zeroes-out the struct. This means the destructor can run multiple times and therefore it is up to the developer to use it safely.
The primary usage case for this is smart-pointer types like `Rc<T>` as the extra flag caused the struct to be 1 word larger because of alignment.
This closes#7271 and #7138
