Re: Fix accidentally cast away qualifiers - Mailing list pgsql-hackers

> On Jan 21, 2026, at 22:56, Bertrand Drouvot <bertranddrouvot.pg@gmail.com> wrote:
>
> Hi,
>
> On Wed, Jan 21, 2026 at 02:24:58PM +0000, Bertrand Drouvot wrote:
>> Hi,
>>
>> 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?
>>
>> It's gcc 14.1.0 with "CFLAGS=-O0 -ggdb3 -fno-omit-frame-pointer -gdwarf-2 -g3
>> -Wdiscarded-qualifiers -Wunused-value -Werror=maybe-uninitialized
>> -Werror=format -Wreturn-type"
>>
>> But I just tested with a simple test case, some compilers and some options and I've
>> always seen the warning (see [1])
>
> FWIW, and so does the CI: https://github.com/bdrouvot/postgres/runs/61028037498
>
> Regards,
>
> --
> Bertrand Drouvot
> PostgreSQL Contributors Team
> RDS Open Source Databases
> Amazon Web Services: https://aws.amazon.com
>

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 *'
discardsqualifiers [-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 *'
discardsqualifiers [-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 *'
discardsqualifiers [-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 *'
discardsqualifiers [-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) == 0x01)
      |         ^
4 warnings generated.
```

I didn’t use any special compiler option, just ran “make”.

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

Sorry, I didn’t 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/