[PATCH 0/2] stdlib: Fix and verify heapsort for two-element cases

[PATCH 0/2] stdlib: Fix and verify heapsort for two-element cases

[Kuan-Wei Chiu]

Ensure correct behavior in cases with exactly two elements, and malloc
fails when allocating a buffer. Additionally, adjust the testing
approach to validate the correctness of heapsort for such cases.

Thanks,
Kuan-Wei

Kuan-Wei Chiu (2):
  stdlib: Fix heapsort for cases with exactly two elements
  stdlib: Verify heapsort for two-element cases

 stdlib/qsort.c      | 2 +-
 stdlib/tst-qsort4.c | 4 +---
 2 files changed, 2 insertions(+), 4 deletions(-)

-- 
2.25.1

[PATCH 1/2] stdlib: Fix heapsort for cases with exactly two elements

[Kuan-Wei Chiu]

When malloc fails to allocate a buffer and falls back to heapsort, the
current heapsort implementation does not perform sorting when there are
exactly two elements. Heapsort is now skipped only when there is
exactly one element.

Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
---
 stdlib/qsort.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/stdlib/qsort.c b/stdlib/qsort.c
index b29882388e..45af8da80c 100644
--- a/stdlib/qsort.c
+++ b/stdlib/qsort.c
@@ -162,7 +162,7 @@ get_swap_type (void *const pbase, size_t size)
 static void
 heapsort_r (void *base, size_t n, size_t size, __compar_d_fn_t cmp, void *arg)
 {
-  if (n <= 1)
+  if (n == 0)
     return;
 
   enum swap_type_t swap_type = get_swap_type (base, size);
-- 
2.25.1

[PATCH 2/2] stdlib: Verify heapsort for two-element cases

[Kuan-Wei Chiu]

Adjust the testing approach to start from scenarios with only 2
elements, as insertion sort no longer handles such cases.

Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
---
 stdlib/tst-qsort4.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/stdlib/tst-qsort4.c b/stdlib/tst-qsort4.c
index 4635275419..247917b454 100644
--- a/stdlib/tst-qsort4.c
+++ b/stdlib/tst-qsort4.c
@@ -96,9 +96,7 @@ do_test (void)
   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)
+  for (int i = 2; i <= 8; ++i)
     {
       signed char *buf = xmalloc (i);
       check_combinations (i, buf, 0);
-- 
2.25.1

Re: [PATCH 1/2] stdlib: Fix heapsort for cases with exactly two elements

[Adhemerval Zanella Netto]

On 15/01/24 23:16, Kuan-Wei Chiu wrote:
> When malloc fails to allocate a buffer and falls back to heapsort, the
> current heapsort implementation does not perform sorting when there are
> exactly two elements. Heapsort is now skipped only when there is
> exactly one element.
> 
> Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>

LGTM, thanks.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

> ---
>  stdlib/qsort.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/stdlib/qsort.c b/stdlib/qsort.c
> index b29882388e..45af8da80c 100644
> --- a/stdlib/qsort.c
> +++ b/stdlib/qsort.c
> @@ -162,7 +162,7 @@ get_swap_type (void *const pbase, size_t size)
>  static void
>  heapsort_r (void *base, size_t n, size_t size, __compar_d_fn_t cmp, void *arg)
>  {
> -  if (n <= 1)
> +  if (n == 0)
>      return;
>  
>    enum swap_type_t swap_type = get_swap_type (base, size);

Re: [PATCH 2/2] stdlib: Verify heapsort for two-element cases

[Adhemerval Zanella Netto]

On 15/01/24 23:16, Kuan-Wei Chiu wrote:
> Adjust the testing approach to start from scenarios with only 2
> elements, as insertion sort no longer handles such cases.
> 
> Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>

LGTM, thanks.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>


> ---
>  stdlib/tst-qsort4.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/stdlib/tst-qsort4.c b/stdlib/tst-qsort4.c
> index 4635275419..247917b454 100644
> --- a/stdlib/tst-qsort4.c
> +++ b/stdlib/tst-qsort4.c
> @@ -96,9 +96,7 @@ do_test (void)
>    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)
> +  for (int i = 2; i <= 8; ++i)
>      {
>        signed char *buf = xmalloc (i);
>        check_combinations (i, buf, 0);

Re: [PATCH 0/2] stdlib: Fix and verify heapsort for two-element cases

[Andreas K. Huettel]

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Am Dienstag, 16. Januar 2024, 03:16:55 CET schrieb Kuan-Wei Chiu:
> Ensure correct behavior in cases with exactly two elements, and malloc
> fails when allocating a buffer. Additionally, adjust the testing
> approach to validate the correctness of heapsort for such cases.
> 
> Thanks,
> Kuan-Wei
> 
> Kuan-Wei Chiu (2):
>   stdlib: Fix heapsort for cases with exactly two elements
>   stdlib: Verify heapsort for two-element cases
> 
>  stdlib/qsort.c      | 2 +-
>  stdlib/tst-qsort4.c | 4 +---
>  2 files changed, 2 insertions(+), 4 deletions(-)

OK


-- 
Andreas K. Hüttel
dilfridge@gentoo.org
Gentoo Linux developer 
(council, comrel, toolchain, base-system, perl, libreoffice)
https://wiki.gentoo.org/wiki/User:Dilfridge

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