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Thread: Compiler warning in costsize.c

Compiler warning in costsize.c

From
Michael Paquier
Date:
Hi all,

In builds where USE_ASSERT_CHECKING is not enabled, costsize.c can
generate warnings. Here is for example with MSVC:
  src/backend/optimizer/path/costsize.c(4520): warning C4101: 'rte' : unreferen
ced local variable [C:\Users\ioltas\git\postgres\postgres.vcxproj]
  src/backend/optimizer/path/costsize.c(4640): warning C4101: 'rte' : unreferen
ced local variable [C:\Users\ioltas\git\postgres\postgres.vcxproj]

a9c074ba7 has done an effort, but a bit more is needed as the attached.

Thanks,
-- 
Michael
Attachment

Re: Compiler warning in costsize.c

From
David Rowley
Date:
On 4 April 2017 at 16:22, Michael Paquier <michael.paquier@gmail.com> wrote:
> Hi all,
>
> In builds where USE_ASSERT_CHECKING is not enabled, costsize.c can
> generate warnings. Here is for example with MSVC:
>   src/backend/optimizer/path/costsize.c(4520): warning C4101: 'rte' : unreferen
> ced local variable [C:\Users\ioltas\git\postgres\postgres.vcxproj]
>   src/backend/optimizer/path/costsize.c(4640): warning C4101: 'rte' : unreferen
> ced local variable [C:\Users\ioltas\git\postgres\postgres.vcxproj]
>
> a9c074ba7 has done an effort, but a bit more is needed as the attached.

Thanks for writing the patch.

I wondering if it would be worth simplifying it a little to get rid of
the double #ifdefs, as per attached.

-- 
 David Rowley                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services
Attachment

Re: Compiler warning in costsize.c

From
Michael Paquier
Date:
On Tue, Apr 4, 2017 at 7:03 PM, David Rowley
<david.rowley@2ndquadrant.com> wrote:
> On 4 April 2017 at 16:22, Michael Paquier <michael.paquier@gmail.com> wrote:
>> Hi all,
>>
>> In builds where USE_ASSERT_CHECKING is not enabled, costsize.c can
>> generate warnings. Here is for example with MSVC:
>>   src/backend/optimizer/path/costsize.c(4520): warning C4101: 'rte' : unreferen
>> ced local variable [C:\Users\ioltas\git\postgres\postgres.vcxproj]
>>   src/backend/optimizer/path/costsize.c(4640): warning C4101: 'rte' : unreferen
>> ced local variable [C:\Users\ioltas\git\postgres\postgres.vcxproj]
>>
>> a9c074ba7 has done an effort, but a bit more is needed as the attached.
>
> Thanks for writing the patch.
>
> I wondering if it would be worth simplifying it a little to get rid of
> the double #ifdefs, as per attached.

Yes, that would be fine as well.
-- 
Michael

Re: Compiler warning in costsize.c

From
Tom Lane
Date:
Michael Paquier <michael.paquier@gmail.com> writes:
> In builds where USE_ASSERT_CHECKING is not enabled, costsize.c can
> generate warnings. Here is for example with MSVC:
>   src/backend/optimizer/path/costsize.c(4520): warning C4101: 'rte' : unreferenced local variable
[C:\Users\ioltas\git\postgres\postgres.vcxproj]
>   src/backend/optimizer/path/costsize.c(4640): warning C4101: 'rte' : unreferenced local variable
[C:\Users\ioltas\git\postgres\postgres.vcxproj]

> a9c074ba7 has done an effort, but a bit more is needed as the attached.

That doesn't look right at all:

+#ifdef USE_ASSERT_CHECKING    RangeTblEntry *rte PG_USED_FOR_ASSERTS_ONLY;
+#endif

The entire point of the PG_USED_FOR_ASSERTS_ONLY annotation is to suppress
this type of warning without a need for an explicit #ifdef like that one.

We should either fix PG_USED_FOR_ASSERTS_ONLY to work on MSVC as well,
or decide that we don't care about suppressing such warnings on MSVC,
or give up on PG_USED_FOR_ASSERTS_ONLY and remove it everywhere in
favor of plain #ifdefs.

(I'm personally not that much in love with PG_USED_FOR_ASSERTS_ONLY,
because it tends to confuse pgindent.)
        regards, tom lane

Re: Compiler warning in costsize.c

From
Michael Paquier
Date:
On Wed, Apr 5, 2017 at 2:54 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Michael Paquier <michael.paquier@gmail.com> writes:
>> In builds where USE_ASSERT_CHECKING is not enabled, costsize.c can
>> generate warnings. Here is for example with MSVC:
>>   src/backend/optimizer/path/costsize.c(4520): warning C4101: 'rte' : unreferenced local variable
[C:\Users\ioltas\git\postgres\postgres.vcxproj]
>>   src/backend/optimizer/path/costsize.c(4640): warning C4101: 'rte' : unreferenced local variable
[C:\Users\ioltas\git\postgres\postgres.vcxproj]
>
>> a9c074ba7 has done an effort, but a bit more is needed as the attached.
>
> That doesn't look right at all:
>
> +#ifdef USE_ASSERT_CHECKING
>         RangeTblEntry *rte PG_USED_FOR_ASSERTS_ONLY;
> +#endif
>
> The entire point of the PG_USED_FOR_ASSERTS_ONLY annotation is to suppress
> this type of warning without a need for an explicit #ifdef like that one.
>
> We should either fix PG_USED_FOR_ASSERTS_ONLY to work on MSVC as well,
> or decide that we don't care about suppressing such warnings on MSVC,
> or give up on PG_USED_FOR_ASSERTS_ONLY and remove it everywhere in
> favor of plain #ifdefs.

Visual does not have any equivalent of __attribute__((unused))... And
visual does not have an equivalent after looking around. A trick that
I can think of would be to change PG_USED_FOR_ASSERTS_ONLY to be
roughly a macro like that:

#if defined(__GNUC__)
#define PG_ASSERT_ONLY(x) ASSERT_ONLY_ ## x __attribute__((unused))
#else
#define PG_ASSERT_ONLY(x) ((void) x)
#endif

But that's ugly...

> (I'm personally not that much in love with PG_USED_FOR_ASSERTS_ONLY,
> because it tends to confuse pgindent.)

I would be incline to just do that, any other solution I can think of
is uglier than that.
-- 
Michael