Re: Refactor compile-time assertion checks for C/C++

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Michael Paquier <michael(at)paquier(dot)xyz>
Cc: Georgios Kokolatos <gkokolatos(at)pm(dot)me>, pgsql-hackers(at)lists(dot)postgresql(dot)org
Subject: Re: Refactor compile-time assertion checks for C/C++
Date: 2020-03-16 14:32:36
Message-ID: 2636.1584369156@sss.pgh.pa.us
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Michael Paquier <michael(at)paquier(dot)xyz> writes:
> On Fri, Mar 13, 2020 at 11:00:33AM -0400, Tom Lane wrote:
>> If we do need to change it, I'd be inclined to just use the do{}
>> block everywhere, not bothering with the extra #if test.

> Not sure what you mean here because we cannot use the do{} flavor
> either for the C fallback, no? See for example the definitions of
> unconstify() in c.h.

Sorry for being unclear --- I just meant that we could use do{}
in StaticAssertStmt for both C and C++. Although now I notice
that the code is trying to use StaticAssertStmt for StaticAssertExpr,
which you're right isn't going to do. But I think something like
this would work and be a bit simpler than what you proposed:

#else
/* Fallback implementation for C and C++ */
#define StaticAssertStmt(condition, errmessage) \
- ((void) sizeof(struct { int static_assert_failure : (condition) ? 1 : -1; }))
+ do { struct static_assert_struct { int static_assert_failure : (condition) ? 1 : -1; }; } while(0)
#define StaticAssertExpr(condition, errmessage) \
- StaticAssertStmt(condition, errmessage)
+ ((void) sizeof(struct { int static_assert_failure : (condition) ? 1 : -1; }))
#define StaticAssertDecl(condition, errmessage) \

regards, tom lane

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