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

From: "Smith, Peter" <peters(at)fast(dot)au(dot)fujitsu(dot)com>
To: Andres Freund <andres(at)anarazel(dot)de>, 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: 2019-10-09 22:52:41
Message-ID: 201DD0641B056142AC8C6645EC1B5F62014B92C7C1@SYD1217
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From: Andres Freund <andres(at)anarazel(dot)de> Sent: Tuesday, 1 October 2019 3:14 AM

>I wonder if defining the fallback static assert code to something like
> extern void static_assert_func(int static_assert_failed[(condition) ? 1 : -1]); isn't a solution, however. I *think* that's standard C. Seems to work at least with gcc, clang, msvc, icc.
>
>Re standard: C99's "6.7 Declarations" + 6.7.1 defines 'declaration' to include extern specifiers and in 6.7.1 5) says "The declaration of an identifier for a function that has block scope shall have >no explicit storage-class specifier other than extern.". And "6.8 Statements and blocks", via "6.8.2 Compound statement" allows declarations in statements.
>
>You can play with a good few compilers at: https://godbolt.org/z/fl0Mzu

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.
https://godbolt.org/z/fDrmXi

The patch has been updated accordingly. All assertions identified in the original post are now adjacent the global variables they are asserting.

Kind Regards
--
Peter Smith
Fujitsu Australia

Attachment Content-Type Size
ct_asserts_StaticAssertDecl_2.patch application/octet-stream 6.6 KB

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