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
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
Use `task_read_for_pid()` rather than having the crashing program pass its
own task port through. This opts us in to additional OS security measures
surrounding the use of this call.
rdar://107362003
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
