Re: Proposal: Add more compile-time asserts to expose inconsistencies.

From: Andres Freund <andres(at)anarazel(dot)de>
To: pgsql-hackers(at)lists(dot)postgresql(dot)org,Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>,"Smith, Peter" <peters(at)fast(dot)au(dot)fujitsu(dot)com>,Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Michael Paquier <michael(at)paquier(dot)xyz>, Dagfinn Ilmari Mannsåker <ilmari(at)ilmari(dot)org>,PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Proposal: Add more compile-time asserts to expose inconsistencies.
Date: 2019-10-27 01:02:46
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On October 26, 2019 6:06:07 AM PDT, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com> wrote:
>On 2019-10-10 00:52, Smith, Peter wrote:
>> I liked your idea of using an extern function declaration for
>implementing the file-scope compile-time asserts. AFAIK it is valid
>standard C.
>> Thank you for the useful link to that compiler explorer. I tried many
>scenarios of the new StaticAssertDecl and all seemed to work ok.
>> The patch has been updated accordingly. All assertions identified in
>the original post are now adjacent the global variables they are
>The problem with this implementation is that you get a crappy error
>message when the assertion fails, namely something like:
>../../../../src/include/c.h:862:84: error: size of array
>'static_assert_failure' is negative

My proposal for this really was just to use this as a fallback for when static assert isn't available. Which in turn I was just suggesting because Tom wanted a fallback.

>Ideally, the implementation should end up calling _Static_assert()
>somehow, so that we get the compiler's native error message.
>We could do a configure check for whether _Static_assert() works at
>scope. I don't know what the support for that is, but it seems to work
>in gcc and clang.

I think it should work everywhere that has static assert. So we should need a separate configure check.

Sent from my Android device with K-9 Mail. Please excuse my brevity.

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