Re: New GNU C Library (glibc) security flaw reported on 30 Jan 2024

[Siddhesh Poyarekar <siddhesh@gotplt.org>]

On 2024-02-01 14:55, Paul Eggert wrote:
> From 8ff74efcc11a77e221808293ed390faf6dea86fe Mon Sep 17 00:00:00 2001
> From: Paul Eggert <eggert@cs.ucla.edu>
> Date: Thu, 1 Feb 2024 11:52:46 -0800
> Subject: [PATCH] stdlib: fix qsort example in manual
> 
> * manual/search.texi (Comparison Functions, Array Sort Function):
> Sort an array of long ints, not doubles, to avoid hassles
> with NaNs.
> ---
>  manual/search.texi | 21 ++++++++++++---------
>  1 file changed, 12 insertions(+), 9 deletions(-)

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

> 
> diff --git a/manual/search.texi b/manual/search.texi
> index ffaadc46f5..db577a5332 100644
> --- a/manual/search.texi
> +++ b/manual/search.texi
> @@ -35,19 +35,22 @@ second, zero if they are ``equal'', and positive if the first argument
>  is ``greater''.
>  
>  Here is an example of a comparison function which works with an array of
> -numbers of type @code{double}:
> +numbers of type @code{long int}:
>  
>  @smallexample
>  int
> -compare_doubles (const void *a, const void *b)
> +compare_long_ints (const void *a, const void *b)
>  @{
> -  const double *da = (const double *) a;
> -  const double *db = (const double *) b;
> +  const long int *la = a;
> +  const long int *lb = b;
>  
> -  return (*da > *db) - (*da < *db);
> +  return (*la > *lb) - (*la < *lb);
>  @}
>  @end smallexample
>  
> +(The code would have to be more complicated for an array of @code{double},
> +to handle NaNs correctly.)
> +
>  The header file @file{stdlib.h} defines a name for the data type of
>  comparison functions.  This type is a GNU extension.
>  
> @@ -183,16 +186,16 @@ in the array before making some comparisons.  The only way to perform
>  a stable sort with @code{qsort} is to first augment the objects with a
>  monotonic counter of some kind.
>  
> -Here is a simple example of sorting an array of doubles in numerical
> +Here is a simple example of sorting an array of @code{long int} in numerical
>  order, using the comparison function defined above (@pxref{Comparison
>  Functions}):
>  
>  @smallexample
>  @{
> -  double *array;
> -  int size;
> +  long int *array;
> +  size_t nmemb;
>    @dots{}
> -  qsort (array, size, sizeof (double), compare_doubles);
> +  qsort (array, nmemb, sizeof *array, compare_long_ints);
>  @}
>  @end smallexample
>  
> -- 
> 2.40.1