Re: Odd behavior with PG_TRY

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Kevin Grittner <kgrittn(at)gmail(dot)com>
Cc: Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Odd behavior with PG_TRY
Date: 2017-01-06 19:24:56
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Kevin Grittner <kgrittn(at)gmail(dot)com> writes:
> On Fri, Jan 6, 2017 at 5:43 AM, Michael Paquier
> <michael(dot)paquier(at)gmail(dot)com> wrote:
>> If a variable is modified within PG_TRY and then referenced in
>> PG_CATCH it needs to be marked as volatile to be strictly in
>> conformance with POSIX. This also ensures that any compiler does not
>> do any stupid optimizations with those variables in the way they are
>> referenced and used.

> That sort of begs the question of why PG_exception_stack is not
> marked as volatile, since the macros themselves modify it within
> the PG_TRY block and reference it within the PG_CATCH block. Is
> there some reason this variable is immune to the problem?

It's not a local variable.

regards, tom lane

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