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Date: Wed, 05 Jul 2023 16:06:46 -0500
Message-Id: <CTUJMJ1B57SL.3T8TKNTE9XSVD@gonk>
Subject: Re: Fix last unitialized memory warning
To: "Peter Eisentraut" <peter@eisentraut.org>,
 <pgsql-hackers@postgresql.org>
From: "Tristan Partin" <tristan@neon.tech>
References: <CT6HJ3U8068R.3A8SJMV02D9BC@gonk>
 <8f7880cc-3622-1c0a-a126-5b47aafeee51@eisentraut.org>
In-Reply-To: <8f7880cc-3622-1c0a-a126-5b47aafeee51@eisentraut.org>
Archived-At: 
 <https://www.postgresql.org/message-id/CTUJMJ1B57SL.3T8TKNTE9XSVD%40gonk>
Precedence: bulk

On Mon Jul 3, 2023 at 1:19 AM CDT, Peter Eisentraut wrote:
> On 07.06.23 16:31, Tristan Partin wrote:
> > This patch is really not necessary from a functional point of view. It
> > is only necessary if we want to silence a compiler warning.
> >=20
> > Tested on `gcc (GCC) 13.1.1 20230511 (Red Hat 13.1.1-2)`.
> >=20
> > After silencing this warning, all I am left with (given my build
> > configuration) is:
> >=20
> > [1667/2280] Compiling C object src/pl/plpgsql/src/plpgsql.so.p/pl_exec.=
c.o
> > In file included from ../src/include/access/htup_details.h:22,
> >                   from ../src/pl/plpgsql/src/pl_exec.c:21:
> > In function =E2=80=98assign_simple_var=E2=80=99,
> >      inlined from =E2=80=98exec_set_found=E2=80=99 at ../src/pl/plpgsql=
/src/pl_exec.c:8349:2:
> > ../src/include/varatt.h:230:36: warning: array subscript 0 is outside a=
rray bounds of =E2=80=98char[0]=E2=80=99 [-Warray-bounds=3D]
> >    230 |         (((varattrib_1b_e *) (PTR))->va_tag)
> >        |                                    ^
> > ../src/include/varatt.h:94:12: note: in definition of macro =E2=80=98VA=
RTAG_IS_EXPANDED=E2=80=99
> >     94 |         (((tag) & ~1) =3D=3D VARTAG_EXPANDED_RO)
> >        |            ^~~
> > ../src/include/varatt.h:284:57: note: in expansion of macro =E2=80=98VA=
RTAG_1B_E=E2=80=99
> >    284 | #define VARTAG_EXTERNAL(PTR)                            VARTAG=
_1B_E(PTR)
> >        |                                                         ^~~~~~=
~~~~~
> > ../src/include/varatt.h:301:57: note: in expansion of macro =E2=80=98VA=
RTAG_EXTERNAL=E2=80=99
> >    301 |         (VARATT_IS_EXTERNAL(PTR) && !VARTAG_IS_EXPANDED(VARTAG=
_EXTERNAL(PTR)))
> >        |                                                         ^~~~~~=
~~~~~~~~~
> > ../src/pl/plpgsql/src/pl_exec.c:8537:17: note: in expansion of macro =
=E2=80=98VARATT_IS_EXTERNAL_NON_EXPANDED=E2=80=99
> >   8537 |                 VARATT_IS_EXTERNAL_NON_EXPANDED(DatumGetPointe=
r(newvalue)))
> >        |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >=20
> >  From my perspective, this warning definitely seems like a false
> > positive, but I don't know the code well-enough to say that for certain=
.
>
> I cannot reproduce this warning with gcc-13.  Are you using any=20
> non-standard optimization options.  Could you give your full configure=20
> and build commands and the OS?

Thanks for following up. My system is Fedora 38. I can confirm this is
still happening on master.

$ gcc --version
gcc (GCC) 13.1.1 20230614 (Red Hat 13.1.1-4)
Copyright (C) 2023 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$ meson setup build --buildtype=3Drelease
$ ninja -C build

--=20
Tristan Partin
Neon (https://neon.tech)