This removes the stacking of type parameters that occurs when invoking
trait methods, and fixes all places in the standard library that were
relying on it. It is somewhat awkward in places; I think we'll probably
want something like the `Foo::<for T>::new()` syntax.
.with_c_str() is a replacement for the old .as_c_str(), to avoid
unnecessary boilerplate.
Replace all usages of .to_c_str().with_ref() with .with_c_str().
This PR fixes#7235 and #3371, which removes trailing nulls from `str` types. Instead, it replaces the creation of c strings with a new type, `std::c_str::CString`, which wraps a malloced byte array, and respects:
* No interior nulls
* Ends with a trailing null
Mostly optimizing TLS accesses to bring local heap allocation performance
closer to that of oldsched. It's not completely at parity but removing the
branches involved in supporting oldsched and optimizing pthread_get/setspecific
to instead use our dedicated TCB slot will probably make up for it.
old design the TLS held the scheduler struct, and the scheduler struct
held the active task. This posed all sorts of weird problems due to
how we wanted to use the contents of TLS. The cleaner approach is to
leave the active task in TLS and have the task hold the scheduler. To
make this work out the scheduler has to run inside a regular task, and
then once that is the case the context switching code is massively
simplified, as instead of three possible paths there is only one. The
logical flow is also easier to follow, as the scheduler struct acts
somewhat like a "token" indicating what is active.
These changes also necessitated changing a large number of runtime
tests, and rewriting most of the runtime testing helpers.
Polish level is "low", as I will very soon start on more scheduler
changes that will require wiping the polish off. That being said there
should be sufficient comments around anything complex to make this
entirely respectable as a standalone commit.
* stop using an atomic counter, this has a significant cost and
valgrind will already catch these leaks
* remove the extra layer of function calls
* remove the assert of non-null in free, freeing null is well defined
but throwing a failure from free will not be
* stop initializing the `prev`/`next` pointers
* abort on out-of-memory, failing won't necessarily work
