[PATCH] argp-parse: Get rid of alloca

[Adhemerval Zanella Netto]

On 13/07/23 09:48, Joe Simmons-Talbott via Libc-alpha wrote:
> Even though the alloca usage is relatively small and fixed size the code
> can be written without using alloca.  Convert to local variables.
> 
> Checked on x86_64-linux-gnu.

You can also remove all the boilerplate that define alloca at the start.

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

> ---
>  argp/argp-parse.c | 20 +++++++++++---------
>  1 file changed, 11 insertions(+), 9 deletions(-)
> 
> diff --git a/argp/argp-parse.c b/argp/argp-parse.c
> index a44b50f8e4..40a5896d21 100644
> --- a/argp/argp-parse.c
> +++ b/argp/argp-parse.c
> @@ -884,6 +884,9 @@ __argp_parse (const struct argp *argp, int argc, char **argv, unsigned flags,
>    error_t err;
>    struct parser parser;
>  
> +  struct argp_child child[4];
> +  struct argp top_argp;
> +
>    /* If true, then err == EBADKEY is a result of a non-option argument failing
>       to be parsed (which in some cases isn't actually an error).  */
>    int arg_ebadkey = 0;
> @@ -891,24 +894,23 @@ __argp_parse (const struct argp *argp, int argc, char **argv, unsigned flags,
>    if (! (flags & ARGP_NO_HELP))
>      /* Add our own options.  */
>      {
> -      struct argp_child *child = alloca (4 * sizeof (struct argp_child));
> -      struct argp *top_argp = alloca (sizeof (struct argp));
> +      int child_index = 0;
>  
>        /* TOP_ARGP has no options, it just serves to group the user & default
>  	 argps.  */
> -      memset (top_argp, 0, sizeof (*top_argp));
> -      top_argp->children = child;
> +      memset (&top_argp, 0, sizeof (struct argp));
> +      top_argp.children = child;
>  
>        memset (child, 0, 4 * sizeof (struct argp_child));
>  
>        if (argp)
> -	(child++)->argp = argp;
> -      (child++)->argp = &argp_default_argp;
> +	child[child_index++].argp = argp;
> +      child[child_index++].argp = &argp_default_argp;
>        if (argp_program_version || argp_program_version_hook)
> -	(child++)->argp = &argp_version_argp;
> -      child->argp = 0;
> +	child[child_index++].argp = &argp_version_argp;
> +      child[child_index].argp = 0;
>  
> -      argp = top_argp;
> +      argp = &top_argp;
>      }
>  
>    /* Construct a parser for these arguments.  */