Re: pg_trgm comparison bug on cross-architecture replication due to different char implementation

Noah Misch <noah(at)leadboat(dot)com> writes:
> On Tue, Oct 01, 2024 at 11:55:48AM -0700, Masahiko Sawada wrote:
>> Considering that the population of database cluster signedness will
>> converge to signedness=true in the future, we can consider using
>> -fsigned-char to prevent similar problems for the future. We need to
>> think about possible side-effects as well, though.

> It's good to think about -fsigned-char. While I find it tempting, several
> things would need to hold for us to benefit from it:

> - Every supported compiler has to offer it or an equivalent.
> - The non-compiler parts of every supported C implementation need to
> cooperate. For example, CHAR_MIN must change in response to the flag. See
> the first comment in cash_in().
> - Libraries we depend on can't do anything incompatible with it.

> Given that, I would lean toward not using -fsigned-char. It's unlikely all
> three things will hold. Even if they do, the benefit is not large.

I am very, very strongly against deciding that Postgres will only
support one setting of char signedness. It's a step on the way to
hardware monoculture, and we know where that eventually leads.
(In other words, I categorically reject Sawada-san's assertion
that signed chars will become universal. I'd reject the opposite
assertion as well.)

regards, tom lane