Horton

Re: shadow variables - pg15 edition

David Rowley <dgrowleyml@gmail.com>

View thread View on postgr.es
From: David Rowley <dgrowleyml@gmail.com>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: Justin Pryzby <pryzby@telsasoft.com>, pgsql-hackers@postgresql.org, Tomas Vondra <tomas.vondra@postgresql.org>, Peter Smith <smithpb2250@gmail.com>
Date: 2022-10-06T20:13:31Z
Lists: pgsql-hackers 
On Thu, 6 Oct 2022 at 20:32, Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:
>
> On 2022-Oct-06, David Rowley wrote:
> > I didn't want to do it that way because all this code is in a while
> > loop and the outer "now" will be reused after it's set by the code
> > above.  It's not really immediately obvious to me what repercussions
> > that would have, but it didn't seem worth taking any risks.
>
> No, it's re-initialized to zero every time through the loop, so setting
> it to something else at the bottom doesn't have any further effect.

Oh yeah, you're right.

> If it were *not* reinitialized every time through the loop, then what
> would happen is that every iteration in the loop (and each operation
> within) would see exactly the same value of "now", because it's only set
> "lazily" (meaning, if already set, don't change it.)

On my misread, that's what I was afraid of changing, but now seeing
that now = 0 at the start of each loop, I understand that
pg_time_now_lazy will get an up-to-date time on each loop.

I'm happy if you want to change it to use the outer scoped variable
instead of the now2 one.

David

Commits

  1. Fix shadow variable in postgres.c

  2. Add -Wshadow=compatible-local to the standard compilation flags

  3. Fix final warnings produced by -Wshadow=compatible-local

  4. Fix final compiler warning produced by -Wshadow=compatible-local

  5. Add optional parameter to PG_TRY() macros

  6. Small refactor to get rid of -Wshadow=compatible-local warning

  7. More -Wshadow=compatible-local warning fixes

  8. Further -Wshadow=compatible-local warning fixes

  9. Further reduce warnings with -Wshadow=compatible-local

  10. Reduce warnings with -Wshadow=compatible-local builds

  11. Remove shadowed local variables that are new in v15