This fixes#13238. It avoids an infinite loop when compiling
the tests with `-g`. Without this change, the debuginfo on
`black_box` prevents the method from being inlined, which
allows llvm to convert `silent_recurse` into a tail-call. This
then loops forever instead of consuming all the stack like it
is supposed to. This patch forces inlining `black_box`, which
triggers the right error.
We really do *not* want TCO to kick in. If it does, we'll never blow the
stack, and never trigger the condition the test is checking for. To that end,
do a meaningless alloc that serves only to get a destructor to run. The
addition of nocapture/noalias seems to have let LLVM do more TCO, which
hurt this testcase.
The printing of the error message on stack overflow had two sometimes false
assumptions previously. The first is that a local task was always available (it
called Local::take) and the second is that it used println! instead of
manually writing.
The first assumption isn't necessarily true because while stack overflow will
likely only be detected in situations that a local task is available, it's not
guaranteed to always be in TLS. For example, during a println! call a task
may be blocking, causing it to be unavailable. By using Local::try_take(), we
can be resilient against these occurrences.
The second assumption could lead to odd behavior because the stdout logger can
be overwritten to run arbitrary code. Currently this should be possible, but the
utility is much diminished because a stack overflow translates to an abort()
instead of a failure.
