Re: Don't pass NULL pointer to strcmp().

Hi Tom,

There're extensions that set their boot_val to NULL. E.g., postgres_fdw (
https://github.com/postgres/postgres/blob/4210b55f598534db9d52c4535b7dcc777dda75a6/contrib/postgres_fdw/option.c#L582)
plperl (
https://github.com/postgres/postgres/blob/4210b55f598534db9d52c4535b7dcc777dda75a6/src/pl/plperl/plperl.c#L422C13-L422C13,
https://github.com/postgres/postgres/blob/4210b55f598534db9d52c4535b7dcc777dda75a6/src/pl/plperl/plperl.c#L444C12-L444C12,
https://github.com/postgres/postgres/blob/4210b55f598534db9d52c4535b7dcc777dda75a6/src/pl/plperl/plperl.c#L452C6-L452C6)
(Can we treat plperl as an extension?), pltcl (
https://github.com/postgres/postgres/blob/4210b55f598534db9d52c4535b7dcc777dda75a6/src/pl/tcl/pltcl.c#L465C14-L465C14,
https://github.com/postgres/postgres/blob/4210b55f598534db9d52c4535b7dcc777dda75a6/src/pl/tcl/pltcl.c#L472C12-L472C12
).

TBH, I don't know if NULL is a valid boot_val for string variables, I just
came across some extensions that use NULL as their boot_val. If the
boot_val can't be NULL in extensions, we should probably add some
assertions or comments about it?

Best Regards,
Xing

On Wed, Nov 1, 2023 at 11:30 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> Xing Guo <higuoxing(at)gmail(dot)com> writes:
> > Thanks for your comments. I have updated the patch accordingly.
>
> I'm leery of accepting this patch, as I see no reason that we
> should consider it valid for an extension to have a string GUC
> with a boot_val of NULL.
>
> I realize that we have a few core GUCs that are like that, but
> I'm pretty sure that every one of them has special-case code
> that initializes the GUC to something non-null a bit later on
> in startup. I don't think there are any cases where a string
> GUC's persistent value will be null, and I don't like the
> idea of considering that to be an allowed case. It would
> open the door to more crash situations, and it brings up the
> old question of how could a user tell NULL from empty string
> (via SHOW or current_setting() or whatever). Besides, what's
> the benefit really?
>
> regards, tom lane
>