Re: [RFA 14/22] Replace two xmallocs with vector

Pedro Alves
2016-10-13T01:17:25Z

On 10/12/2016 11:39 PM, Tom Tromey wrote:
>>>>>> "Pedro" == Pedro Alves <palves@redhat.com> writes:
>
>>> * cli/cli-dump.c (dump_memory_to_file): Use std::vector.
>>> (restore_binary_file): Likewise.
>
> Pedro> As general guideline, for these cases where we only need to
> Pedro> construct a buffer once (never resize/reallocate) and we don't
> Pedro> care about the initial contents of the buffer, I think
> Pedro> unique_ptr<char[]> buf (new char[size]);
> Pedro> ends up being more efficient, because std::vector
> Pedro> default/zero initializes its elements, which is unnecessary since
> Pedro> we're about to write into the buffer anyway.
>
> Pedro> WDYT?
>
> It's fine with me.
>
> Often the performance doesn't matter, and std::vector is safe to use.
> On the other hand XNEWVEC isn't really unsafe -- maybe just mildly less
> clear to gdb newbies.

Hmm, the code you're touching isn't using XNEWVEC, so I'm not sure
I know exactly what you're referring to, but I assume you're thinking
of the xmallocs you're replacing.

Both vector and unique_ptr<T[]> (or unique_malloc_ptr<T> with the
to go with the existing mallocs) have the advantage of not requiring a
cleanup, of course. Writing either I think is almost the same code.
I think unique_ptr communicates intent a little better for these
cases, with the added bonus of a little extra efficiency, but it's not
a huge issue.

Thanks,
Pedro Alves