Re: Consistently use palloc_object() and palloc_array()

David Geier <geidav(dot)pg(at)gmail(dot)com> writes:
> On 27.11.2025 00:03, Chao Li wrote:
>> This is a large patch, I just take a quick look, and found that:
>> - *phoned_word = palloc(sizeof(char) * strlen(word) + 1);
>> + *phoned_word = palloc_array(char, strlen(word) + 1);
>> And
>> - params = (const char **) palloc(sizeof(char *));
>> + params = palloc_object(const char *);
>> Applying palloc_array and palloc_object to char type doesn’t seem to improve anything.

> You mean because sizeof(char) is always 1 and hence we could instead
> simply write:
> *phoned_word = palloc(strlen(word) + 1);
> params = palloc(1);
> I think the _array and _object variants are more expressive and for sure
> don't make the code less readable.

Yeah, I agree these particular changes seem fine. When you're doing
address arithmetic for a memcpy or such, it may be fine to wire in an
assumption that sizeof(char) == 1, but I think doing that in other
contexts is not particularly good style.

Another thing to note is that the proposed patch effectively changes
the expression evaluation order:

- *phoned_word = palloc((sizeof(char) * strlen(word)) + 1);
+ *phoned_word = palloc(sizeof(char) * (strlen(word) + 1));

Now, there's not actually any difference because sizeof(char) is 1,
but if it hypothetically weren't, the new version is likely more
correct. Presumably the +1 is meant to allow room for a trailing \0,
which is a char.

It'd be a good idea to review the patch to see if there are any
places where semantics are changed in a less benign fashion...

regards, tom lane