% File src/library/base/man/Cstack_info.Rd
% Part of the R package, https://www.R-project.org
% Copyright 1995-2016 R Core Team
% Distributed under GPL 2 or later

\name{Cstack_info}
\alias{Cstack_info}
\title{Report Information on C Stack Size and Usage}
\description{
  Report information on the C stack size and usage (if available).
}
\usage{
Cstack_info()
}
\details{
  On most platforms, C stack information is recorded when \R is
  initialized and used for stack-checking.  If this information is
  unavailable, the \code{size} will be returned as \code{NA}, and
  stack-checking is not performed.

  %% Reports in Feb 2016 that this is broken by 'musl' on Linux.
  The information on the stack base address is thought to be accurate on
  Windows, Linux (using \code{glibc}), macOS and FreeBSD but a heuristic
  is used on other platforms.  Because this might be slightly
  inaccurate, the current usage could be estimated as negative.  (The
  heuristic is not used on embedded uses of \R on platforms where the
  stack base information is not thought to be accurate.)

  The \sQuote{evaluation depth} is the number of nested \R expressions
  currently under evaluation: this has a limit controlled by
  \code{\link{options}("expressions")}.
}
\value{
  An integer vector.  This has named elements
  \item{size}{The size of the stack (in bytes), or \code{NA} if unknown.}
  \item{current}{The estimated current usage (in bytes), possibly \code{NA}.}
  \item{direction}{\code{1} (stack grows down, the usual case) or
    \code{-1} (stack grows up).}
  \item{eval_depth}{The current evaluation depth (including two calls
    for the call to \code{Cstack_info}).}
}
\examples{\donttest{
Cstack_info()
}}
\keyword{ utilities }