Horton

Re: printf %s with NULL pointer (was Re: BUG #17098: Assert failed on composing an error message when adding a type to an extension being dropped)

Ranier Vilela <ranier.vf@gmail.com>

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From: Ranier Vilela <ranier.vf@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Laurenz Albe <laurenz.albe@cybertec.at>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2021-07-13T18:04:19Z
Lists: pgsql-bugs, pgsql-hackers 
Em ter., 13 de jul. de 2021 às 11:29, Tom Lane <tgl@sss.pgh.pa.us> escreveu:

> Laurenz Albe <laurenz.albe@cybertec.at> writes:
> > On Mon, 2021-07-12 at 13:20 -0400, Tom Lane wrote:
> >> So my feeling about this is that switching snprintf.c's behavior
> >> would produce some net gain in robustness for v12 and up, while
> >> not making things any worse for the older branches.  I still hold
> >> to the opinion that we've already flushed out all the cases of
> >> passing NULL that we're likely to find via ordinary testing.
>
> > New cases could be introduced in the future and might remain undetected.
> > What about adding an Assert that gags on NULLs, but still printing them
> > as "(null)"?  That would help find such problems in a debug build.
>
> I think you're missing my main point, which is that it seems certain that
> there are corner cases that do this *now*.  I'm proposing that we redefine
> this as not being a crash case, full stop.
>
I agree with Laurenz Albe, that on Debug builds, *printf with NULL, must
crash.
On production builds, fine, printing (null).
This will put a little more pressure on support, "Hey what mean's (null) in
my logs?",
but it's ok.

regards,
Ranier Vilela

Commits

  1. Make printf("%s", NULL) print "(null)" instead of crashing.

  2. Lock the extension during ALTER EXTENSION ADD/DROP.

  3. Add an assertion that we don't pass NULL to snprintf("%s").

  4. Fix broken logic for reporting PL/Python function names in errcontext.