define: DUK_USE_VALSTACK_SHRINK_SLACK_SHIFT
introduced: 2.2.0
default: 4
tags:
  - performance
  - lowmemory
description: >
  When shrinking, leave (curr_size >> DUK_USE_VALSTACK_SHRINK_SLACK_SHIFT)
  bytes as a slack.  This shift count must be larger than
  DUK_USE_VALSTACK_SHRINK_CHECK_SHIFT.