Re: [REPORT] Static analys warnings

From: Andres Freund <andres(at)anarazel(dot)de>
To: Ranier Vilela <ranier(dot)vf(at)gmail(dot)com>
Cc: PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: [REPORT] Static analys warnings
Date: 2020-05-03 21:20:12
Message-ID: 20200503212012.penuxcee6btvw5be@alap3.anarazel.de
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On 2020-05-03 17:05:54 -0300, Ranier Vilela wrote:
> 1. Warning: the right operand to | always evaluates to 0
>
> src/include/storage/bufpage.h
> #define PAI_OVERWRITE (1 << 0)
> #define PAI_IS_HEAP (1 << 1)
>
> #define PageAddItem(page, item, size, offsetNumber, overwrite, is_heap) \
> PageAddItemExtended(page, item, size, offsetNumber, \
> ((overwrite) ? PAI_OVERWRITE : 0) | \
> ((is_heap) ? PAI_IS_HEAP : 0))
>
> Typo | should be ||:
> ((overwrite) ? PAI_OVERWRITE : 0) || \
> ((is_heap) ? PAI_IS_HEAP : 0))

Definitely not. PageAddItemExtended's flags argument is not a boolean,
it's a flag bitmask. It'd entirely break the semantics to make the
change you suggest.

Nor do I know what this warning is about, because clearly in the general
case the right argument to the | does not generally evaluate to 0. I
guess this about a particular use of the macro (with a constant
argument), rather than the macro itself.

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