Build failure with -Werror=format-overflow in cgroup.c with -O3

[thesamesam]

systemd version the issue has been seen with

master (78b95cc)

Used distribution

Gentoo

Linux kernel version used

6.6.2

CPU architectures issue was seen on

x86_64

Component

systemd

Expected behaviour you didn't see

Successful build.

Unexpected behaviour you saw

Build failure because of a -Werror=format-overflow warning.

FAILED: src/core/libsystemd-core-255.so.p/cgroup.c.o
ccache cc -Isrc/core/libsystemd-core-255.so.p -Isrc/core -I../src/core -Isrc/basic -I../src/basic -Isrc/fundamental -I../src/fundamental -Isrc/systemd -I../src/systemd -I. -I.. -I../src/libsystemd/sd-bus -I../src/libsystemd/sd-device -I../src/libsystemd/sd-event -I../src/libsystemd/sd-hwdb -I../src/libsystemd/sd-id128 -I../src/libsystemd/sd-journal -I../src/libsystemd/sd-netlink -I../src/libsystemd/sd-network -I../src/libsystemd/sd-resolve -Isrc/shared -I../src/shared -I/usr/include/blkid -I/usr/include/libmount -I/usr/include/security -fdiagnostics-color=always -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -Wextra -std=gnu11 -O0 -g -Wno-missing-field-initializers -Wno-unused-parameter -Warray-bounds -Warray-bounds=2 -Wdate-time -Wendif-labels -Werror=format=2 -Werror=format-signedness -Werror=implicit-function-declaration -Werror=implicit-int -Werror=incompatible-pointer-types -Werror=int-conversion -Werror=missing-declarations -Werror=missing-prototypes -Werror=overflow -Werror=override-init -Werror=return-type -Werror=shift-count-overflow -Werror=shift-overflow=2 -Werror=strict-flex-arrays -Werror=undef -Wfloat-equal -Wimplicit-fallthrough=5 -Winit-self -Wlogical-op -Wmissing-include-dirs -Wmissing-noreturn -Wnested-externs -Wold-style-definition -Wpointer-arith -Wredundant-decls -Wshadow -Wstrict-aliasing=2 -Wstrict-prototypes -Wsuggest-attribute=noreturn -Wunused-function -Wwrite-strings -Wzero-length-bounds -fdiagnostics-show-option -fno-common -fstack-protector -fstack-protector-strong -fstrict-flex-arrays --param=ssp-buffer-size=4 -Wno-maybe-uninitialized -Wno-unused-result -Werror=shadow -O3 -fno-semantic-interposition -fPIC -fno-strict-aliasing -fstrict-flex-arrays=1 -fvisibility=hidden -fno-omit-frame-pointer -include config.h -pthread -fvisibility=default -MD -MQ src/core/libsystemd-core-255.so.p/cgroup.c.o -MF src/core/libsystemd-core-255.so.p/cgroup.c.o.d -o src/core/libsystemd-core-255.so.p/cgroup.c.o -c ../src/core/cgroup.c
../src/core/cgroup.c: In function ‘cgroup_context_dump’:
../src/core/cgroup.c:633:44: error: ‘%s’ directive argument is null [-Werror=format-overflow=]
  633 |                         "%sDeviceAllow: %s %s\n",
      |                                            ^~
cc1: some warnings being treated as errors
ninja: build stopped: subcommand failed.

I've hit variants of this a few times, not just with -O3 -fno-semantic-interposition (sometimes just -O3 or even -O2 is enough on alt. arches).

Steps to reproduce the problem

CC=gcc-13 CFLAGS="-O3 -fno-semantic-interposition" meson setup build

Additional program output to the terminal or log subsystem illustrating the issue

No response

[thesamesam]

We hit a another one downstream on s390 with just -O3 in src/shared/install.c (https://bugs.gentoo.org/916518) but with 254.5:

In file included from ../systemd-stable-254.5/src/basic/macro.h:446,
                 from ../systemd-stable-254.5/src/basic/alloc-util.h:10,
                 from ../systemd-stable-254.5/src/shared/install.c:12:
../systemd-stable-254.5/src/shared/install.c: In function ‘install_changes_dump’:
../systemd-stable-254.5/src/shared/install.c:444:64: error: ‘%s’ directive argument is null [-Werror=format-overflow=]
  444 |                         err = log_error_errno(changes[i].type, "Failed to %s unit, unit %s does not exist.",

[thesamesam]

Thank you!