Subclause [stacktrace] describes components
that C++ programs may use to store
the stacktrace of the current thread of execution and
query information about the stored stacktrace at runtime.
The invocation sequence of the current evaluation x0
in the current thread of execution
is a sequence (x0,…,xn) of evaluations such that, for i ≥ 0,
xi is within the function invocation xi+1 ([intro.execution]).