The double-panic `abort` is run after the logging code, to provide
feedback in case of a double-panic. This means that if the panic
logging fails with a panic, the `abort` might never be reached.
This should not normally occur, but if the `on_panic` function detects
more than 2 panics, aborting *before* logging makes panic handling
somewhat more robust, as it avoids an infinite recursion, which would
eventually crash the process, but also make the problem harder to
debug.
This handles the FIXME about what to do if the thread printing panics.
Move the panic handling logic from the `unwind` module to `panicking`
and use a panic counter to distinguish between normal state, panics
and double panics.
This commit does some refactoring to make almost all of the `std::rt` private.
Specifically, the following items are no longer part of its API:
* DEFAULT_ERROR_CODE
* backtrace
* unwind
* args
* at_exit
* cleanup
* heap (this is just alloc::heap)
* min_stack
* util
The module is now tagged as `#[doc(hidden)]` as the only purpose it's serve is
an entry point for the `panic!` macro via the `begin_unwind` and
`begin_unwind_fmt` reexports.
Closes#25977
The various `stdfoo_raw` methods in std::io now return `io::Result`s,
since they may not exist on Windows. They will always return `Ok` on
Unix-like platforms.
[breaking-change]
Inspecting the current thread's info may not always work due to the TLS value
having been destroyed (or is actively being destroyed). The code for printing
a panic message assumed, however, that it could acquire the thread's name
through this method.
Instead this commit propagates the `Option` outwards to allow the
`std::panicking` module to handle the case where the current thread isn't
present.
While it solves the immediate issue of #24313, there is still another underlying
issue of panicking destructors in thread locals will abort the process.
Closes#24313
