text: /* sort.c -- Sort without allocating memory
     Copyright (C) 2012-2018 Free Software Foundation, Inc.
     Written by Ian Lance Taylor, Google.
  
  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions are
  met:
  
      (1) Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.
  
      (2) Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in
      the documentation and/or other materials provided with the
      distribution.
  
      (3) The name of the author may not be used to
      endorse or promote products derived from this software without
      specific prior written permission.
  
  THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
  INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
  IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  POSSIBILITY OF SUCH DAMAGE.  */
  
  #include "config.h"
  
  #include <stddef.h>
  #include <sys/types.h>
  
  #include "backtrace.h"
  #include "internal.h"
  
  /* The GNU glibc version of qsort allocates memory, which we must not
     do if we are invoked by a signal handler.  So provide our own
     sort.  */
  
  static void
  swap (char *a, char *b, size_t size)
  {
    size_t i;
  
    for (i = 0; i < size; i++, a++, b++)
      {
        char t;
  
        t = *a;
        *a = *b;
        *b = t;
      }
  }
  
  void
  backtrace_qsort (void *basearg, size_t count, size_t size,
  		 int (*compar) (const void *, const void *))
  {
    char *base = (char *) basearg;
    size_t i;
    size_t mid;
  
   tail_recurse:
    if (count < 2)
      return;
  
    /* The symbol table and DWARF tables, which is all we use this
       routine for, tend to be roughly sorted.  Pick the middle element
       in the array as our pivot point, so that we are more likely to
       cut the array in half for each recursion step.  */
    swap (base, base + (count / 2) * size, size);
  
    mid = 0;
    for (i = 1; i < count; i++)
      {
        if ((*compar) (base, base + i * size) > 0)
  	{
  	  ++mid;
  	  if (i != mid)
  	    swap (base + mid * size, base + i * size, size);
  	}
      }
  
    if (mid > 0)
      swap (base, base + mid * size, size);
  
    /* Recurse with the smaller array, loop with the larger one.  That
       ensures that our maximum stack depth is log count.  */
    if (2 * mid < count)
      {
        backtrace_qsort (base, mid, size, compar);
        base += (mid + 1) * size;
        count -= mid + 1;
        goto tail_recurse;
      }
    else
      {
        backtrace_qsort (base + (mid + 1) * size, count - (mid + 1),
  		       size, compar);
        count = mid;
        goto tail_recurse;
      }
  }
  