When we crash, emit a message straight away that says we're working
on a backtrace. If starting the backtracer fails, report that also.
Finally, add a duration to the messages output by the backtracer, so
that we can see how long it took.
rdar://118055527
We have two stacks that we set up during crash handling, both of
which were potentially misaligned. This only tripped us up on
Ubuntu 20.04 on aarch64 - my guess is that maybe `clone()` aligns
the stack pointer on newer kernels which is why we didn't see it
on 22.04.
rdar://110743884
`__cxa_demangle()` is a rather unusual API; one of its "features" is that
the pointer you pass in must either be `nullptr`, in which case it
will call `malloc()` itself, _or_ it has to be a pointer to a block
of memory allocated with `malloc()`, because `__cxa_demangle()` may
`realloc()` it for you.
This seems to me to be something of a non-obvious footgun, so we never
pass the caller's pointer through to `__cxa_demangle()`, which lets them
decide how they want to allocate space.
rdar://110261712
The `status` argument to the `_swift_backtrace_demangle()` function
isn't especially useful, won't match behaviour on Windows, and we
actually don't use it in the Swift code that calls this SPI.
Remove it.
rdar://110261712
Use the new module structure rather the old SwiftShims header. This
is much cleaner and lets us include operating system headers to get
the relevant definitions where possible.
Add code to support ELF and DWARF, including decompression using
zlib, zstd and liblzma if those turn out to be required and available.
rdar://110261712
Mike and Max made various helpful suggestions, so I've added and updated
various comments and amended the code to cope with partial reads and
writes.
rdar://110261430
This also adds a function to demangle a symbol, and a way for the
backtracing code to report warning messages to the same place as
the main runtime.
I'd like to rename the _swift_isThunkFunction() SPI also, but we
can't do that until we've made the changes to the _Backtracing
library, so we'll do that there instead.
rdar://110261430
Some symbolication frameworks have a symbol cache; we probably don't want
to use that for test cases, to avoid running into problems where the cache
holds stale information.
rdar://105409147
We really, really shouldn't be running the external backtracer for setuid
binaries. It's just too dangerous.
So don't do that. And if someone tries to force us, emit a warning.
rdar://105391747
