[glibc] stdlib: Avoid another self-comparison in qsort

[Florian Weimer <fw@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=e4d8117b82065dc72e8df80097360e7c05a349b9

commit e4d8117b82065dc72e8df80097360e7c05a349b9
Author: Florian Weimer <fweimer@redhat.com>
Date:   Tue Nov 21 16:45:35 2023 +0100

    stdlib: Avoid another self-comparison in qsort
    
    In the insertion phase, we could run off the start of the array if the
    comparison function never runs zero.  In that case, it never finds the
    initial element that terminates the iteration.
    
    Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

Diff:
---
 stdlib/qsort.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/stdlib/qsort.c b/stdlib/qsort.c
index ad110e8a89..6d0c4447ec 100644
--- a/stdlib/qsort.c
+++ b/stdlib/qsort.c
@@ -217,7 +217,7 @@ insertion_sort_qsort_partitions (void *const pbase, size_t total_elems,
   while ((run_ptr += size) <= end_ptr)
     {
       tmp_ptr = run_ptr - size;
-      while (cmp (run_ptr, tmp_ptr, arg) < 0)
+      while (run_ptr != tmp_ptr && cmp (run_ptr, tmp_ptr, arg) < 0)
         tmp_ptr -= size;
 
       tmp_ptr += size;