Re: [PATCH v3] libctf: ctf_member_next needs to return (ssize_t)-1 on error

[Nick Alcock <nick.alcock@oracle.com>]

On 13 Sep 2023, Torbjörn SVENSSON verbalised:

> v1 -> v2:
> Changed all functions with signed interger return type to return -1 based on
> comment from Alan.
>
> v2 -> v3:
> Added ctf_set_errno_signed function to return a signed -1 value based on
> comment from Nick.
>
> Ok for trunk?

If this touches exactly those functions that return int, and fixes the
reported bug, it's good as far as I'm concerned, except for a couple of
possible comment improvements:

> +/* Store the specified error code into the CTF dict, and then return -1
> +   (CTF_ERR) for the benefit of the caller. */

It's not CTF_ERR in this case, it's just -1. Perhaps:

/* Store the specified error code into the CTF dict, and then return -1
   for the benefit of the caller, which is expected to return int,
   as opposed to ctf_id_t. */

> +int
> +ctf_set_errno_signed (ctf_dict_t *fp, int err)
> +{
> +  fp->ctf_errno = err;
> +  /* Don't rely on CTF_ERR here as it will not properly sign extend on 64-bit
> +     Windows ABI.  */
> +  return -1;
> +}

... that Windows is not really the problem here. It's more

/* Don't rely on CTF_ERR here; it is a ctf_id_t (unsigned long), and
   it will be truncated to a non--1 value on platforms on which int
   and unsigned long are different sizes.  */

perhaps? (At least, I think that's what's going on.)

This probably needs testing on a wide variety of platforms with
different type sizes. I'll add throwing this through my entire test
matrix to my todo list, and fix any bugs observed: but the basic idea
looks sound to me.

-- 
NULL && (void)