glibc/sysdeps/generic/malloc-sysdep.h

/* System-specific malloc support functions.  Generic version.
   Copyright (C) 2012-2016 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <http://www.gnu.org/licenses/>.  */

#include <stdbool.h>
#include <unistd.h>

/* Force an unmap when the heap shrinks in a secure exec.  This ensures that
   the old data pages immediately cease to be accessible.  */
static inline bool
check_may_shrink_heap (void)
{
  return __libc_enable_secure;
}