/* sort.c -- Sort without allocating memory   Copyright (C) 2012-2026 Free Software Foundation, Inc.   Written by Ian Lance Taylor, Google. Redistribution and use in source and binary forms, with or withoutmodification, are permitted provided that the following conditions aremet:     (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 ORIMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIEDWARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE AREDISCLAIMED. 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 ORSERVICES; 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) ARISINGIN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THEPOSSIBILITY 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 voidswap (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;    }} voidbacktrace_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;    }}