Re: Compiler warning in costsize.c

On 8 April 2017 at 04:42, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> I'd be happier with something along the line of
>
> RangeTblEntry *rte;
> ListCell *lc;
>
> /* Should only be applied to base relations that are subqueries */
> Assert(rel->relid > 0);
> rte = planner_rt_fetch(rel->relid, root);
> #ifdef USE_ASSERT_CHECKING
> Assert(rte->rtekind == RTE_SUBQUERY);
> #else
> (void) rte; /* silence unreferenced-variable complaints */
> #endif

the (void) rte; would not be required to silence MSVC here. Of course,
PG_USED_FOR_ASSERTS_ONLY would be required to stop some smarter
compiler from complaining.

> assuming that that actually does silence the warning on MSVC.
>
> BTW, is it really true that only these two places produce such warnings
> on MSVC? I see about three dozen uses of PG_USED_FOR_ASSERTS_ONLY in our
> tree, and I'd have expected all of those places to be causing warnings on
> a compiler that doesn't have a way to understand that annotation.

Seems that MSVC is happy once the variable is assigned, and does not
bother checking if the variable is used after being assigned, whereas,
some other compilers might see the variable as uselessly assigned.

At the moment there are no other warnings from MSVC since all the
other places the variable gets assigned a value in some code path.

--
David Rowley http://www.2ndQuadrant.com/
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