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Subject: BUG #19485: Compilation warnings and notes with GCC 16.1.1 on new
 Fedora 44
To: pgsql-bugs@lists.postgresql.org
From: PG Bug reporting form <noreply@postgresql.org>
Cc: buschmann@nidsa.net
Reply-To: buschmann@nidsa.net, pgsql-bugs@lists.postgresql.org
Date: Mon, 18 May 2026 07:06:44 +0000
Message-ID: <19485-2b03231a775756f1@postgresql.org>
Auto-Submitted: auto-generated
Archived-At: 
 <https://www.postgresql.org/message-id/19485-2b03231a775756f1%40postgresql.org>
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The following bug has been logged on the website:

Bug reference:      19485
Logged by:          Hans Buschmann
Email address:      buschmann@nidsa.net
PostgreSQL version: 18.4
Operating system:   Fedora 44 Server x86-64
Description:       =20

When compiling the new current minor version 18.4 on fedora with GCC 16.1.1
I stumbled over two warnings/notes:

[root@fedora build]# ninja
[813/2272] Compiling C object
src/backend/postgres_lib.a.p/optimizer_util_clauses.c.o
../src/backend/optimizer/util/clauses.c: In function
=E2=80=98recheck_cast_function_args.isra=E2=80=99:
../src/backend/optimizer/util/clauses.c:4403:19: warning: =E2=80=98actual_a=
rg_types=E2=80=99
may be used uninitialized [-Wmaybe-uninitialized]
 4403 |         rettype =3D enforce_generic_type_consistency(actual_arg_typ=
es,
      |                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 4404 |
declared_arg_types,
      |
~~~~~~~~~~~~~~~~~~~
 4405 |
nargs,
      |
~~~~~~
 4406 |
funcform->prorettype,
      |
~~~~~~~~~~~~~~~~~~~~~
 4407 |
false);
      |
~~~~~~
In file included from ../src/backend/optimizer/util/clauses.c:42:
../src/include/parser/parse_coerce.h:85:17: note: by argument 1 of type
=E2=80=98const Oid *=E2=80=99 {aka =E2=80=98const unsigned int *=E2=80=99} =
to
=E2=80=98enforce_generic_type_consistency=E2=80=99 declared here
   85 | extern Oid      enforce_generic_type_consistency(const Oid
*actual_arg_types,
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../src/backend/optimizer/util/clauses.c:4389:33: note: =E2=80=98actual_arg_=
types=E2=80=99
declared here
 4389 |         Oid                     actual_arg_types[FUNC_MAX_ARGS];
      |                                 ^~~~~~~~~~~~~~~~
[2272/2272] Linking target src/interfaces/ecpg/test/pg_regress_ecpg
[root@fedora build]#


The same occurs also with the development branch snapshot 19devel from
18.5.2026

Since I cannot attach a file here I show the summary of my meson
configuration:


meson setup build --prefix=3D/usr/local/pgbeta -Dpgport=3D5431 -Duuid=3Dossp

...
...
postgresql 18.4

  Data layout
    data block size        : 8 kB
    WAL block size         : 8 kB
    segment size           : 1 GB

  System
    host system            : linux x86_64
    build system           : linux x86_64

  Compiler
    linker                 : ld.bfd
    C compiler             : gcc 16.1.1

  Compiler Flags
    CPP FLAGS              : -D_GNU_SOURCE
    C FLAGS, functional    : -fno-strict-aliasing -fwrapv
-fexcess-precision=3Dstandard
    C FLAGS, warnings      : -Wmissing-prototypes -Wpointer-arith
-Werror=3Dvla -Wendif-labels -Wmissing-format-attribute
-Wimplicit-fallthrough=3D3 -Wcast-function-type -Wshadow=3Dcompatible-local
-Wformat-security -Wdeclaration-after-statement
-Wmissing-variable-declarations -Wno-format-truncation
-Wno-stringop-truncation
    C FLAGS, modules       : -fvisibility=3Dhidden
    C FLAGS, user specified:
    LD FLAGS               :

  Programs
    bison                  : /usr/bin/bison 3.8.2
    dtrace                 : NO
    flex                   : /usr/bin/flex 2.6.4

  External libraries
    bonjour                : NO
    bsd_auth               : NO
    docs                   : YES
    docs_pdf               : NO
    gss                    : NO
    icu                    : YES 77.1
    ldap                   : NO
    libcurl                : NO
    libnuma                : YES 2.0.19
    liburing               : YES 2.13
    libxml                 : YES 2.12.10
    libxslt                : NO
    llvm                   : NO
    lz4                    : YES 1.10.0
    nls                    : YES
    openssl                : YES 3.5.5
    pam                    : NO
    plperl                 : YES 5.42.2
    plpython               : YES 3.14
    pltcl                  : NO
    readline               : YES 8.3
    selinux                : YES 3.10
    systemd                : YES 259
    uuid                   : YES 1.6.2
    zlib                   : YES 1.3.1.zlib-ng
    zstd                   : YES 1.5.7

  User defined options
    pgport                 : 5431
    prefix                 : /usr/local/pgbeta
    uuid                   : ossp

Found ninja-1.13.2 at /usr/bin/ninja
#

As I am not an expert C programmer, please could somebody check the
combination of Postgres and GCC 16.1.1 to resolve this minor issue.

Only checked 18.4 and 19devel, only with GCC (not Clang), no other versions.

Thank you for looking

Hans Buschmann