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Subject: Re: Fix accidentally cast away qualifiers
From: Chao Li <li.evan.chao@gmail.com>
In-Reply-To: <aXDpJUt5QenOlPSl@ip-10-97-1-34.eu-west-3.compute.internal>
Date: Thu, 22 Jan 2026 16:22:24 +0800
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
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To: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>,
 Peter Eisentraut <peter@eisentraut.org>
Archived-At: 
 <https://www.postgresql.org/message-id/5C33CCDF-7A95-4757-B35A-CA62C2D77F31%40gmail.com>
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> On Jan 21, 2026, at 22:56, Bertrand Drouvot =
<bertranddrouvot.pg@gmail.com> wrote:
>=20
> Hi,
>=20
> On Wed, Jan 21, 2026 at 02:24:58PM +0000, Bertrand Drouvot wrote:
>> Hi,
>>=20
>> On Wed, Jan 21, 2026 at 12:31:27PM +0100, Peter Eisentraut wrote:
>>> Strange, I don't see that.  What compiler is this, and do you use =
any
>>> special options?
>>=20
>> It's gcc 14.1.0 with "CFLAGS=3D-O0 -ggdb3 -fno-omit-frame-pointer =
-gdwarf-2 -g3
>> -Wdiscarded-qualifiers -Wunused-value -Werror=3Dmaybe-uninitialized
>> -Werror=3Dformat -Wreturn-type"
>>=20
>> But I just tested with a simple test case, some compilers and some =
options and I've
>> always seen the warning (see [1])
>=20
> FWIW, and so does the CI: =
https://github.com/bdrouvot/postgres/runs/61028037498
>=20
> Regards,
>=20
> --=20
> Bertrand Drouvot
> PostgreSQL Contributors Team
> RDS Open Source Databases
> Amazon Web Services: https://aws.amazon.com
>=20

Yeah, I confirm I can see the same warnings:
```
In file included from xlogdesc.c:21:
In file included from ../../../src/include/utils/guc.h:17:
In file included from ../../../src/include/utils/array.h:65:
In file included from ../../../src/include/utils/expandeddatum.h:47:
../../../src/include/varatt.h:307:9: warning: returning 'const char[]' =
from a function with result type 'char *' discards qualifiers =
[-Wincompatible-pointer-types-discards-qualifiers]
  307 |         return VARDATA_4B(PTR);
      |                ^~~~~~~~~~~~~~~
../../../src/include/varatt.h:261:26: note: expanded from macro =
'VARDATA_4B'
  261 | #define VARDATA_4B(PTR)         (((const varattrib_4b *) =
(PTR))->va_4byte.va_data)
      |                                 =
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../../../src/include/varatt.h:321:9: warning: returning 'const char[]' =
from a function with result type 'char *' discards qualifiers =
[-Wincompatible-pointer-types-discards-qualifiers]
  321 |         return VARDATA_1B(PTR);
      |                ^~~~~~~~~~~~~~~
../../../src/include/varatt.h:263:26: note: expanded from macro =
'VARDATA_1B'
  263 | #define VARDATA_1B(PTR)         (((const varattrib_1b *) =
(PTR))->va_data)
      |                                 =
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../../../src/include/varatt.h:342:9: warning: returning 'const char[]' =
from a function with result type 'char *' discards qualifiers =
[-Wincompatible-pointer-types-discards-qualifiers]
  342 |         return VARDATA_1B_E(PTR);
      |                ^~~~~~~~~~~~~~~~~
../../../src/include/varatt.h:264:27: note: expanded from macro =
'VARDATA_1B_E'
  264 | #define VARDATA_1B_E(PTR)       (((const varattrib_1b_e *) =
(PTR))->va_data)
      |                                 =
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../../../src/include/varatt.h:488:9: warning: returning 'const char *' =
from a function with result type 'char *' discards qualifiers =
[-Wincompatible-pointer-types-discards-qualifiers]
  488 |         return VARATT_IS_1B(PTR) ? VARDATA_1B(PTR) : =
VARDATA_4B(PTR);
      |                =
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../../../src/include/varatt.h:235:2: note: expanded from macro =
'VARATT_IS_1B'
  235 |         ((((const varattrib_1b *) (PTR))->va_header & 0x01) =3D=3D=
 0x01)
      |         ^
4 warnings generated.
```

I didn=E2=80=99t use any special compiler option, just ran =E2=80=9Cmake=E2=
=80=9D.

My configure is:
```
./configure --enable-debug --enable-cassert --enable-tap-tests =
--enable-depend
```

Sorry, I didn=E2=80=99t notice the warnings in my first review. I guess =
I left my desktop while building at the time.

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/