[PATCH] check_native: Get rid of alloca

[Florian Weimer]

* Andreas Schwab:

> On Jun 01 2023, Florian Weimer via Libc-alpha wrote:
>
>> * Adhemerval Zanella Netto via Libc-alpha:
>>
>>> +static void
>>> +iclose (int *fd)
>>> +{
>>> +  if (*fd >= 0)
>>> +    __close_nocancel_nostatus (*fd);
>>> +}
>>> +
>>>  void
>>>  __check_native (uint32_t a1_index, int *a1_native,
>>>  		uint32_t a2_index, int *a2_native)
>>>  {
>>> -  int fd = __socket (PF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, NETLINK_ROUTE);
>>> +  int __attribute__ ((__cleanup__ (iclose))) fd
>>> +    = __socket (PF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, NETLINK_ROUTE);
>>> +  if (fd < 0)
>>> +    return;
>>
>> I think introducing attribute cleanup where equivalent functionality can
>> be implemented otherwise requires a discussion first.
>
> The cleanup attribute requires compiling the function and all callees
> with -fasynchronous-unwind-tables.

I think GCC will still call the destructor on normal scope exit (if no
exception is thrown), even with -fno-exceptions.  That should be
sufficient here?

Thanks,
Florian