Re: Nicely exiting PG_TRY and PG_CATCH

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Mikhail Gribkov <youzhick(at)gmail(dot)com>
Cc: pgsql-hackers(at)lists(dot)postgresql(dot)org
Subject: Re: Nicely exiting PG_TRY and PG_CATCH
Date: 2022-10-07 21:19:03
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Mikhail Gribkov <youzhick(at)gmail(dot)com> writes:
> Usually it's not a good idea to exit PG_TRY() block via return statement.
> Otherwise it would leave PG_exception_stack global variable in a wrong
> state and next ereport() will jump to some junk address.

Yeah, you can't return or goto out of the PG_TRY part.

> Another suspicious case is PG_CATCH block in jsonb_plpython.c:

This should be OK. The PG_CATCH and PG_FINALLY macros are set up so that
we've fully restored that state *before* we execute any of the
error-handling code. It would be basically impossible to have a guarantee
that CATCH blocks never throw errors; they'd be so restricted as to be
near useless, like signal handlers.

regards, tom lane

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