glibc/stdlib/tst-qsort4.c
Florian Weimer 55364e1f7d stdlib: Handle various corner cases in the fallback heapsort for qsort
The previous implementation did not consistently apply the rule that
the child nodes of node K are at 2 * K + 1 and 2 * K + 2, or
that the parent node is at (K - 1) / 2.

Add an internal test that targets the heapsort implementation
directly.

Reported-by: Stepan Golosunov <stepan@golosunov.pp.ru>
Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
2023-11-21 16:46:02 +01:00

135 lines
3.8 KiB
C

/* Test the heapsort implementation behind qsort.
Copyright (C) 2023 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 "qsort.c"
#include <stdio.h>
#include <support/check.h>
#include <support/support.h>
static int
cmp (const void *a1, const void *b1, void *closure)
{
const signed char *a = a1;
const signed char *b = b1;
return *a - *b;
}
/* Wrapper around heapsort_r that set ups the required variables. */
static void
heapsort_wrapper (void *const pbase, size_t total_elems, size_t size,
__compar_d_fn_t cmp, void *arg)
{
char *base_ptr = (char *) pbase;
char *lo = base_ptr;
char *hi = &lo[size * (total_elems - 1)];
if (total_elems <= 1)
/* Avoid lossage with unsigned arithmetic below. */
return;
enum swap_type_t swap_type;
if (is_aligned (pbase, size, 8))
swap_type = SWAP_WORDS_64;
else if (is_aligned (pbase, size, 4))
swap_type = SWAP_WORDS_32;
else
swap_type = SWAP_BYTES;
heapsort_r (lo, hi, size, swap_type, cmp, arg);
}
static void
check_one_sort (signed char *array, int length)
{
signed char *copy = xmalloc (length);
memcpy (copy, array, length);
heapsort_wrapper (copy, length, 1, cmp, NULL);
/* Verify that the result is sorted. */
for (int i = 1; i < length; ++i)
if (copy[i] < copy[i - 1])
{
support_record_failure ();
printf ("error: sorting failure for length %d at offset %d\n",
length, i - 1);
printf ("input:");
for (int i = 0; i < length; ++i)
printf (" %d", array[i]);
printf ("\noutput:");
for (int i = 0; i < length; ++i)
printf (" %d", copy[i]);
putchar ('\n');
break;
}
/* Verify that no elements went away or were added. */
{
int expected_counts[256];
for (int i = 0; i < length; ++i)
++expected_counts[array[i] & 0xff];
int actual_counts[256];
for (int i = 0; i < length; ++i)
++actual_counts[copy[i] & 0xff];
for (int i = 0; i < 256; ++i)
TEST_COMPARE (expected_counts[i], expected_counts[i]);
}
free (copy);
}
/* Enumerate all possible combinations of LENGTH elements. */
static void
check_combinations (int length, signed char *start, int offset)
{
if (offset == length)
check_one_sort (start, length);
else
for (int i = 0; i < length; ++i)
{
start[offset] = i;
check_combinations(length, start, offset + 1);
}
}
static int
do_test (void)
{
/* A random permutation of 20 values. */
check_one_sort ((signed char[20]) {5, 12, 16, 10, 14, 11, 9, 13, 8, 15,
0, 17, 3, 7, 1, 18, 2, 19, 4, 6}, 20);
/* A permutation that appeared during adversarial testing for the
quicksort pass. */
check_one_sort ((signed char[16]) {15, 3, 4, 2, 1, 0, 8, 7, 6, 5, 14,
13, 12, 11, 10, 9}, 16);
/* Array lengths 2 and less are not handled by heapsort_r and
deferred to insertion sort. */
for (int i = 3; i <= 8; ++i)
{
signed char *buf = xmalloc (i);
check_combinations (i, buf, 0);
free (buf);
}
return 0;
}
#include <support/test-driver.c>