meson: enable -Wzero-as-null-pointer-constant (#36028)

Support for C added in gcc 15:

https://github.com/gcc-mirror/gcc/commit/236c0829ee21a179c81b83f0d7f112ca23c47a4d

36 files changed, 65 insertions, 50 deletions

diff --git a/meson.build b/meson.build
index de92fbe771..5c364e1379 100644
--- a/meson.build
+++ b/meson.build
@@ -412,6 +412,7 @@ possible_common_cc_flags = [
         '-Wunterminated-string-initialization',
         '-Wunused-function',
         '-Wwrite-strings',
+        '-Wzero-as-null-pointer-constant',
         '-Wzero-length-bounds',
 
         # negative arguments are correctly detected starting with meson 0.46.
diff --git a/src/basic/MurmurHash2.c b/src/basic/MurmurHash2.c
index 43a89a0820..bb4cd6b906 100644
--- a/src/basic/MurmurHash2.c
+++ b/src/basic/MurmurHash2.c
@@ -16,9 +16,7 @@
 
 #include "MurmurHash2.h"
 
-#if __GNUC__ >= 7
 _Pragma("GCC diagnostic ignored \"-Wimplicit-fallthrough\"")
-#endif
 
 //-----------------------------------------------------------------------------
 // Platform-specific functions and macros
diff --git a/src/basic/filesystems-gperf.gperf b/src/basic/filesystems-gperf.gperf
index c82fe98227..23c9372af2 100644
--- a/src/basic/filesystems-gperf.gperf
+++ b/src/basic/filesystems-gperf.gperf
@@ -1,5 +1,8 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 %{
+#if __GNUC__ >= 15
+_Pragma("GCC diagnostic ignored \"-Wzero-as-null-pointer-constant\"")
+#endif
 #include <linux/magic.h>
 
 #include "filesystems.h"
diff --git a/src/basic/locale-util.c b/src/basic/locale-util.c
index 23565273dd..09bdb37300 100644
--- a/src/basic/locale-util.c
+++ b/src/basic/locale-util.c
@@ -276,8 +276,7 @@ int locale_is_installed(const char *name) {
         if (STR_IN_SET(name, "C", "POSIX")) /* These ones are always OK */
                 return true;
 
-        _cleanup_(freelocalep) locale_t loc =
-                newlocale(LC_ALL_MASK, name, 0);
+        _cleanup_(freelocalep) locale_t loc = newlocale(LC_ALL_MASK, name, (locale_t) 0);
         if (loc == (locale_t) 0)
                 return errno == ENOMEM ? -ENOMEM : false;
 
diff --git a/src/basic/lock-util.c b/src/basic/lock-util.c
index db9905cb48..7dad009c1e 100644
--- a/src/basic/lock-util.c
+++ b/src/basic/lock-util.c
@@ -231,7 +231,7 @@ int lock_generic_with_timeout(int fd, LockType type, int operation, usec_t timeo
                         .sigev_notify = SIGEV_SIGNAL,
                         .sigev_signo = SIGALRM,
                 };
-                timer_t id = 0;
+                timer_t id;
 
                 if (timer_create(CLOCK_MONOTONIC, &sev, &id) < 0) {
                         log_error_errno(errno, "Failed to allocate CLOCK_MONOTONIC timer: %m");
diff --git a/src/core/load-fragment-gperf.gperf.in b/src/core/load-fragment-gperf.gperf.in
index 1033d08103..1363d7903f 100644
--- a/src/core/load-fragment-gperf.gperf.in
+++ b/src/core/load-fragment-gperf.gperf.in
@@ -268,8 +268,9 @@
 {%- endmacro -%}
 
 %{
-#if __GNUC__ >= 7
 _Pragma("GCC diagnostic ignored \"-Wimplicit-fallthrough\"")
+#if __GNUC__ >= 15
+_Pragma("GCC diagnostic ignored \"-Wzero-as-null-pointer-constant\"")
 #endif
 #include <stddef.h>
 #include "all-units.h"
diff --git a/src/core/manager.c b/src/core/manager.c
index 1b629b1378..72b9290dc0 100644
--- a/src/core/manager.c
+++ b/src/core/manager.c
@@ -2002,7 +2002,7 @@ static void manager_preset_all(Manager *m) {
         UnitFilePresetMode mode =
                 ENABLE_FIRST_BOOT_FULL_PRESET ? UNIT_FILE_PRESET_FULL : UNIT_FILE_PRESET_ENABLE_ONLY;
 
-        r = unit_file_preset_all(RUNTIME_SCOPE_SYSTEM, 0, NULL, mode, NULL, 0);
+        r = unit_file_preset_all(RUNTIME_SCOPE_SYSTEM, 0, NULL, mode, NULL, NULL);
         if (r < 0)
                 log_full_errno(r == -EEXIST ? LOG_NOTICE : LOG_WARNING, r,
                                "Failed to populate /etc with preset unit settings, ignoring: %m");
diff --git a/src/fundamental/macro-fundamental.h b/src/fundamental/macro-fundamental.h
index 35758b5b18..709657dd28 100644
--- a/src/fundamental/macro-fundamental.h
+++ b/src/fundamental/macro-fundamental.h
@@ -84,10 +84,10 @@
 #  define _alloc_(...) __attribute__((__alloc_size__(__VA_ARGS__)))
 #endif
 
-#if __GNUC__ >= 7 || (defined(__clang__) && __clang_major__ >= 10)
-#  define _fallthrough_ __attribute__((__fallthrough__))
-#else
+#if defined(__clang__) && __clang_major__ < 10
 #  define _fallthrough_
+#else
+#  define _fallthrough_ __attribute__((__fallthrough__))
 #endif
 
 #define XSTRINGIFY(x) #x
diff --git a/src/home/homed-gperf.gperf b/src/home/homed-gperf.gperf
index 39aca35b08..d5b798a411 100644
--- a/src/home/homed-gperf.gperf
+++ b/src/home/homed-gperf.gperf
@@ -1,7 +1,8 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 %{
-#if __GNUC__ >= 7
 _Pragma("GCC diagnostic ignored \"-Wimplicit-fallthrough\"")
+#if __GNUC__ >= 15
+_Pragma("GCC diagnostic ignored \"-Wzero-as-null-pointer-constant\"")
 #endif
 #include <stddef.h>
 #include "conf-parser.h"
diff --git a/src/home/homed-manager.c b/src/home/homed-manager.c
index de7c3d8dbe..bb4ad1f99f 100644
--- a/src/home/homed-manager.c
+++ b/src/home/homed-manager.c
@@ -1455,7 +1455,7 @@ static int manager_generate_key_pair(Manager *m) {
         if (r < 0)
                 return log_error_errno(r, "Failed to open key file for writing: %m");
 
-        if (PEM_write_PrivateKey(fprivate, m->private_key, NULL, NULL, 0, NULL, 0) <= 0)
+        if (PEM_write_PrivateKey(fprivate, m->private_key, NULL, NULL, 0, NULL, NULL) <= 0)
                 return log_error_errno(SYNTHETIC_ERRNO(EIO), "Failed to write private key pair.");
 
         r = fflush_sync_and_check(fprivate);
diff --git a/src/journal/journald-gperf.gperf b/src/journal/journald-gperf.gperf
index 49987f5fae..317cfb6426 100644
--- a/src/journal/journald-gperf.gperf
+++ b/src/journal/journald-gperf.gperf
@@ -1,7 +1,8 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 %{
-#if __GNUC__ >= 7
 _Pragma("GCC diagnostic ignored \"-Wimplicit-fallthrough\"")
+#if __GNUC__ >= 15
+_Pragma("GCC diagnostic ignored \"-Wzero-as-null-pointer-constant\"")
 #endif
 #include <stddef.h>
 #include <sys/socket.h>
diff --git a/src/libsystemd/sd-hwdb/sd-hwdb.c b/src/libsystemd/sd-hwdb/sd-hwdb.c
index 588fb0313b..90cf80f199 100644
--- a/src/libsystemd/sd-hwdb/sd-hwdb.c
+++ b/src/libsystemd/sd-hwdb/sd-hwdb.c
@@ -319,7 +319,7 @@ static int hwdb_new(const char *path, sd_hwdb **ret) {
         if (file_offset_beyond_memory_size(hwdb->st.st_size))
                 return log_debug_errno(SYNTHETIC_ERRNO(EFBIG), "File %s is too long.", path);
 
-        hwdb->map = mmap(0, hwdb->st.st_size, PROT_READ, MAP_SHARED, fileno(hwdb->f), 0);
+        hwdb->map = mmap(NULL, hwdb->st.st_size, PROT_READ, MAP_SHARED, fileno(hwdb->f), 0);
         if (hwdb->map == MAP_FAILED)
                 return log_debug_errno(errno, "Failed to map %s: %m", path);
 
diff --git a/src/libsystemd/sd-journal/lookup3.c b/src/libsystemd/sd-journal/lookup3.c
index c2a640687c..8e3dac05af 100644
--- a/src/libsystemd/sd-journal/lookup3.c
+++ b/src/libsystemd/sd-journal/lookup3.c
@@ -55,9 +55,7 @@ on 1 byte), but shoehorning those bytes into integers efficiently is messy.
 # include <endian.h>    /* attempt to define endianness */
 #endif
 
-#if __GNUC__ >= 7
 _Pragma("GCC diagnostic ignored \"-Wimplicit-fallthrough\"")
-#endif
 
 /*
  * My best guess at if you are big-endian or little-endian.  This may
diff --git a/src/login/logind-gperf.gperf b/src/login/logind-gperf.gperf
index e7f39fed2a..f09387e6a8 100644
--- a/src/login/logind-gperf.gperf
+++ b/src/login/logind-gperf.gperf
@@ -1,7 +1,8 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 %{
-#if __GNUC__ >= 7
 _Pragma("GCC diagnostic ignored \"-Wimplicit-fallthrough\"")
+#if __GNUC__ >= 15
+_Pragma("GCC diagnostic ignored \"-Wzero-as-null-pointer-constant\"")
 #endif
 #include <stddef.h>
 #include "conf-parser.h"
diff --git a/src/network/netdev/netdev-gperf.gperf b/src/network/netdev/netdev-gperf.gperf
index be010665c5..be61e208a0 100644
--- a/src/network/netdev/netdev-gperf.gperf
+++ b/src/network/netdev/netdev-gperf.gperf
@@ -1,7 +1,8 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 %{
-#if __GNUC__ >= 7
 _Pragma("GCC diagnostic ignored \"-Wimplicit-fallthrough\"")
+#if __GNUC__ >= 15
+_Pragma("GCC diagnostic ignored \"-Wzero-as-null-pointer-constant\"")
 #endif
 #include <stddef.h>
 #include "bareudp.h"
diff --git a/src/network/networkd-gperf.gperf b/src/network/networkd-gperf.gperf
index 21e8d12690..2eb847d119 100644
--- a/src/network/networkd-gperf.gperf
+++ b/src/network/networkd-gperf.gperf
@@ -1,7 +1,8 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 %{
-#if __GNUC__ >= 7
 _Pragma("GCC diagnostic ignored \"-Wimplicit-fallthrough\"")
+#if __GNUC__ >= 15
+_Pragma("GCC diagnostic ignored \"-Wzero-as-null-pointer-constant\"")
 #endif
 #include <stddef.h>
 #include "conf-parser.h"
diff --git a/src/network/networkd-network-gperf.gperf b/src/network/networkd-network-gperf.gperf
index dc462b690c..9a25be666b 100644
--- a/src/network/networkd-network-gperf.gperf
+++ b/src/network/networkd-network-gperf.gperf
@@ -1,7 +1,8 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 %{
-#if __GNUC__ >= 7
 _Pragma("GCC diagnostic ignored \"-Wimplicit-fallthrough\"")
+#if __GNUC__ >= 15
+_Pragma("GCC diagnostic ignored \"-Wzero-as-null-pointer-constant\"")
 #endif
 #include <netinet/icmp6.h>
 #include <stddef.h>
diff --git a/src/nspawn/nspawn-gperf.gperf b/src/nspawn/nspawn-gperf.gperf
index 123ef0c6c8..4356e0f4fa 100644
--- a/src/nspawn/nspawn-gperf.gperf
+++ b/src/nspawn/nspawn-gperf.gperf
@@ -1,7 +1,8 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 %{
-#if __GNUC__ >= 7
 _Pragma("GCC diagnostic ignored \"-Wimplicit-fallthrough\"")
+#if __GNUC__ >= 15
+_Pragma("GCC diagnostic ignored \"-Wzero-as-null-pointer-constant\"")
 #endif
 #include <stddef.h>
 #include "conf-parser.h"
diff --git a/src/oom/test-oomd-util.c b/src/oom/test-oomd-util.c
index 53109c160d..d124132e0b 100644
--- a/src/oom/test-oomd-util.c
+++ b/src/oom/test-oomd-util.c
@@ -330,7 +330,7 @@ static void test_oomd_mem_and_swap_free_below(void) {
 
 static void test_oomd_sort_cgroups(void) {
         _cleanup_hashmap_free_ Hashmap *h = NULL;
-        _cleanup_free_ OomdCGroupContext **sorted_cgroups;
+        _cleanup_free_ OomdCGroupContext **sorted_cgroups = NULL;
         char **paths = STRV_MAKE("/herp.slice",
                                  "/herp.slice/derp.scope",
                                  "/herp.slice/derp.scope/sheep.service",
@@ -408,12 +408,11 @@ static void test_oomd_sort_cgroups(void) {
         assert_se(oomd_sort_cgroup_contexts(h, compare_pgscan_rate_and_memory_usage, "/herp.slice/derp.scope", &sorted_cgroups) == 2);
         assert_se(sorted_cgroups[0] == &ctx[2]);
         assert_se(sorted_cgroups[1] == &ctx[1]);
-        assert_se(sorted_cgroups[2] == 0);
-        assert_se(sorted_cgroups[3] == 0);
-        assert_se(sorted_cgroups[4] == 0);
-        assert_se(sorted_cgroups[5] == 0);
-        assert_se(sorted_cgroups[6] == 0);
-        sorted_cgroups = mfree(sorted_cgroups);
+        ASSERT_NULL(sorted_cgroups[2]);
+        ASSERT_NULL(sorted_cgroups[3]);
+        ASSERT_NULL(sorted_cgroups[4]);
+        ASSERT_NULL(sorted_cgroups[5]);
+        ASSERT_NULL(sorted_cgroups[6]);
 }
 
 static void test_oomd_fetch_cgroup_oom_preference(void) {
diff --git a/src/resolve/generate-dns_type-gperf.py b/src/resolve/generate-dns_type-gperf.py
index 0d818fb3d9..0fd003a802 100755
--- a/src/resolve/generate-dns_type-gperf.py
+++ b/src/resolve/generate-dns_type-gperf.py
@@ -10,8 +10,9 @@ name, prefix, input = sys.argv[1:]
 
 print("""\
 %{
-#if __GNUC__ >= 7
 _Pragma("GCC diagnostic ignored \\"-Wimplicit-fallthrough\\"")
+#if __GNUC__ >= 15
+_Pragma("GCC diagnostic ignored \\"-Wzero-as-null-pointer-constant\\"")
 #endif
 %}""")
 print("""\
diff --git a/src/resolve/resolved-dnssd-gperf.gperf b/src/resolve/resolved-dnssd-gperf.gperf
index a5158390c9..b31b30ec6e 100644
--- a/src/resolve/resolved-dnssd-gperf.gperf
+++ b/src/resolve/resolved-dnssd-gperf.gperf
@@ -1,5 +1,8 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 %{
+#if __GNUC__ >= 15
+_Pragma("GCC diagnostic ignored \"-Wzero-as-null-pointer-constant\"")
+#endif
 #include <stddef.h>
 #include "conf-parser.h"
 #include "resolved-dnssd.h"
diff --git a/src/resolve/resolved-gperf.gperf b/src/resolve/resolved-gperf.gperf
index 68839352f5..d311754e76 100644
--- a/src/resolve/resolved-gperf.gperf
+++ b/src/resolve/resolved-gperf.gperf
@@ -1,7 +1,8 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 %{
-#if __GNUC__ >= 7
 _Pragma("GCC diagnostic ignored \"-Wimplicit-fallthrough\"")
+#if __GNUC__ >= 15
+_Pragma("GCC diagnostic ignored \"-Wzero-as-null-pointer-constant\"")
 #endif
 #include <stddef.h>
 #include "conf-parser.h"
diff --git a/src/shared/mount-util.c b/src/shared/mount-util.c
index 0d8a1f68eb..39aa3d3ec8 100644
--- a/src/shared/mount-util.c
+++ b/src/shared/mount-util.c
@@ -542,7 +542,7 @@ int mount_switch_root_full(const char *path, unsigned long mount_propagation_fla
         if (mount_propagation_flag == 0)
                 return 0;
 
-        if (mount(NULL, ".", NULL, mount_propagation_flag | MS_REC, 0) < 0)
+        if (mount(NULL, ".", NULL, mount_propagation_flag | MS_REC, NULL) < 0)
                 return log_debug_errno(errno, "Failed to turn new rootfs '%s' into %s mount: %m",
                                        mount_propagation_flag_to_string(mount_propagation_flag), path);
 
diff --git a/src/shared/numa-util.c b/src/shared/numa-util.c
index a954ea349e..b4f815277a 100644
--- a/src/shared/numa-util.c
+++ b/src/shared/numa-util.c
@@ -72,7 +72,7 @@ int apply_numa_policy(const NUMAPolicy *policy) {
 
         assert(policy);
 
-        if (get_mempolicy(NULL, NULL, 0, 0, 0) < 0 && errno == ENOSYS)
+        if (get_mempolicy(NULL, NULL, 0, NULL, 0) < 0 && errno == ENOSYS)
                 return -EOPNOTSUPP;
 
         if (!numa_policy_is_valid(policy))
diff --git a/src/shared/tpm2-util.c b/src/shared/tpm2-util.c
index 29d9dbbe2e..b4ae74f17a 100644
--- a/src/shared/tpm2-util.c
+++ b/src/shared/tpm2-util.c
@@ -5201,8 +5201,8 @@ static int tpm2_calculate_seal_ecc_seed(
         r = ecc_pkey_to_curve_x_y(
                         parent_pkey,
                         &curve_id,
-                        /* ret_x= */ NULL, /* ret_x_size= */ 0,
-                        /* ret_y= */ NULL, /* ret_y_size= */ 0);
+                        /* ret_x= */ NULL, /* ret_x_size= */ NULL,
+                        /* ret_y= */ NULL, /* ret_y_size= */ NULL);
         if (r < 0)
                 return r;
 
diff --git a/src/shared/vpick.c b/src/shared/vpick.c
index c2ca800af5..08f6dd72d9 100644
--- a/src/shared/vpick.c
+++ b/src/shared/vpick.c
@@ -151,7 +151,7 @@ static int pin_choice(
                 r = chaseat(toplevel_fd,
                             inode_path,
                             CHASE_AT_RESOLVE_IN_ROOT,
-                            FLAGS_SET(flags, PICK_RESOLVE) ? &resolved_path : 0,
+                            FLAGS_SET(flags, PICK_RESOLVE) ? &resolved_path : NULL,
                             inode_fd < 0 ? &inode_fd : NULL);
                 if (r < 0)
                         return r;
diff --git a/src/socket-activate/socket-activate.c b/src/socket-activate/socket-activate.c
index 9234bb33cd..134ed3f0de 100644
--- a/src/socket-activate/socket-activate.c
+++ b/src/socket-activate/socket-activate.c
@@ -284,7 +284,7 @@ static int install_chld_handler(void) {
                 .sa_handler = sigchld_hdl,
         };
 
-        if (sigaction(SIGCHLD, &act, 0) < 0)
+        if (sigaction(SIGCHLD, &act, NULL) < 0)
                 return log_error_errno(errno, "Failed to install SIGCHLD handler: %m");
 
         return 0;
diff --git a/src/test/test-fileio.c b/src/test/test-fileio.c
index 60b568b2d2..dbd175ad70 100644
--- a/src/test/test-fileio.c
+++ b/src/test/test-fileio.c
@@ -955,7 +955,7 @@ TEST(read_full_file_socket) {
                 _cleanup_close_ int rfd = -EBADF;
                 /* child */
 
-                rfd = accept4(listener, NULL, 0, SOCK_CLOEXEC);
+                rfd = accept4(listener, NULL, NULL, SOCK_CLOEXEC);
                 assert_se(rfd >= 0);
 
                 assert_se(getpeername(rfd, &peer.sa, &peerlen) >= 0);
diff --git a/src/test/test-mempress.c b/src/test/test-mempress.c
index 44f1f4cf5f..dfbd63e601 100644
--- a/src/test/test-mempress.c
+++ b/src/test/test-mempress.c
@@ -43,7 +43,7 @@ static void *fake_pressure_thread(void *p) {
         ASSERT_STREQ(buf, "hello");
         assert_se(write(cfd, &(const char) { 'z' }, 1) == 1);
 
-        return 0;
+        return NULL;
 }
 
 static int fake_pressure_callback(sd_event_source *s, void *userdata) {
diff --git a/src/test/test-netlink-manual.c b/src/test/test-netlink-manual.c
index 8c1b0d407e..913998ad50 100644
--- a/src/test/test-netlink-manual.c
+++ b/src/test/test-netlink-manual.c
@@ -82,7 +82,7 @@ static int test_tunnel_configure(sd_netlink *rtnl) {
         assert_se(sd_netlink_message_close_container(m) >= 0);
         assert_se(sd_netlink_message_close_container(m) >= 0);
 
-        assert_se(sd_netlink_call(rtnl, m, -1, 0) == 1);
+        ASSERT_OK_POSITIVE(sd_netlink_call(rtnl, m, -1, NULL));
 
         ASSERT_NULL((m = sd_netlink_message_unref(m)));
 
@@ -108,7 +108,7 @@ static int test_tunnel_configure(sd_netlink *rtnl) {
         assert_se(sd_netlink_message_close_container(n) >= 0);
         assert_se(sd_netlink_message_close_container(n) >= 0);
 
-        assert_se(sd_netlink_call(rtnl, n, -1, 0) == 1);
+        ASSERT_OK_POSITIVE(sd_netlink_call(rtnl, n, -1, NULL));
 
         ASSERT_NULL((n = sd_netlink_message_unref(n)));
 
diff --git a/src/test/test-seccomp.c b/src/test/test-seccomp.c
index b400908978..d006e8b7b0 100644
--- a/src/test/test-seccomp.c
+++ b/src/test/test-seccomp.c
@@ -487,7 +487,7 @@ TEST(restrict_address_families) {
                 safe_close(fd);
 
                 assert_se(s = set_new(NULL));
-                assert_se(set_put(s, INT_TO_PTR(AF_UNIX)) >= 0);
+                ASSERT_OK(set_put(s, INT_TO_PTR(AF_UNIX)));
 
                 assert_se(seccomp_restrict_address_families(s, false) >= 0);
 
@@ -510,7 +510,7 @@ TEST(restrict_address_families) {
 
                 set_clear(s);
 
-                assert_se(set_put(s, INT_TO_PTR(AF_INET)) >= 0);
+                ASSERT_OK(set_put(s, INT_TO_PTR(AF_INET)));
 
                 assert_se(seccomp_restrict_address_families(s, true) >= 0);
 
@@ -751,7 +751,7 @@ TEST(restrict_archs) {
                 assert_se(s = set_new(NULL));
 
 #ifdef __x86_64__
-                assert_se(set_put(s, UINT32_TO_PTR(SCMP_ARCH_X86+1)) >= 0);
+                ASSERT_OK(set_put(s, UINT32_TO_PTR(SCMP_ARCH_X86+1)));
 #endif
                 assert_se(seccomp_restrict_archs(s) >= 0);
 
@@ -901,7 +901,7 @@ TEST(native_syscalls_filtered) {
                 /* Passing "native" or an empty set is equivalent, just do both here. */
                 assert_se(arch_s = set_new(NULL));
                 assert_se(seccomp_restrict_archs(arch_s) >= 0);
-                assert_se(set_put(arch_s, SCMP_ARCH_NATIVE) >= 0);
+                ASSERT_OK(set_put(arch_s, (void*) SCMP_ARCH_NATIVE));
                 assert_se(seccomp_restrict_archs(arch_s) >= 0);
 
                 assert_se(access("/", F_OK) >= 0);
diff --git a/src/timesync/timesyncd-gperf.gperf b/src/timesync/timesyncd-gperf.gperf
index 731dea12e3..5543813f2d 100644
--- a/src/timesync/timesyncd-gperf.gperf
+++ b/src/timesync/timesyncd-gperf.gperf
@@ -1,7 +1,8 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 %{
-#if __GNUC__ >= 7
 _Pragma("GCC diagnostic ignored \"-Wimplicit-fallthrough\"")
+#if __GNUC__ >= 15
+_Pragma("GCC diagnostic ignored \"-Wzero-as-null-pointer-constant\"")
 #endif
 #include <stddef.h>
 #include "conf-parser.h"
diff --git a/src/udev/generate-keyboard-keys-gperf.sh b/src/udev/generate-keyboard-keys-gperf.sh
index 9f4364c172..fc34e4bd80 100755
--- a/src/udev/generate-keyboard-keys-gperf.sh
+++ b/src/udev/generate-keyboard-keys-gperf.sh
@@ -6,8 +6,9 @@ set -eu
 awk '
     BEGIN {
         print "%{\n\
-#if __GNUC__ >= 7\n\
 _Pragma(\"GCC diagnostic ignored \\\"-Wimplicit-fallthrough\\\"\")\n\
+#if __GNUC__ >= 15\n\
+_Pragma(\"GCC diagnostic ignored \\\"-Wzero-as-null-pointer-constant\\\"\")\n\
 #endif\n\
 %}"
         print "struct key_name { const char* name; unsigned short id; };"
diff --git a/src/udev/net/link-config-gperf.gperf b/src/udev/net/link-config-gperf.gperf
index e4db56e844..61e7d62410 100644
--- a/src/udev/net/link-config-gperf.gperf
+++ b/src/udev/net/link-config-gperf.gperf
@@ -1,7 +1,8 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 %{
-#if __GNUC__ >= 7
 _Pragma("GCC diagnostic ignored \"-Wimplicit-fallthrough\"")
+#if __GNUC__ >= 15
+_Pragma("GCC diagnostic ignored \"-Wzero-as-null-pointer-constant\"")
 #endif
 #include <stddef.h>
 #include "conf-parser.h"
diff --git a/src/userdb/userdbctl.c b/src/userdb/userdbctl.c
index 74057f6593..e47c3761d0 100644
--- a/src/userdb/userdbctl.c
+++ b/src/userdb/userdbctl.c
@@ -98,7 +98,7 @@ static int show_user(UserRecord *ur, Table *table) {
                 break;
 
         case OUTPUT_JSON:
-                sd_json_variant_dump(ur->json, arg_json_format_flags, NULL, 0);
+                sd_json_variant_dump(ur->json, arg_json_format_flags, NULL, NULL);
                 break;
 
         case OUTPUT_FRIENDLY:
@@ -540,7 +540,7 @@ static int show_group(GroupRecord *gr, Table *table) {
         }
 
         case OUTPUT_JSON:
-                sd_json_variant_dump(gr->json, arg_json_format_flags, NULL, 0);
+                sd_json_variant_dump(gr->json, arg_json_format_flags, NULL, NULL);
                 break;
 
         case OUTPUT_FRIENDLY:
diff --git a/tools/generate-gperfs.py b/tools/generate-gperfs.py
index 3887bb6ee9..1e22a61406 100755
--- a/tools/generate-gperfs.py
+++ b/tools/generate-gperfs.py
@@ -16,8 +16,9 @@ if __name__ == '__main__':
 
     print("""\
 %{
-#if __GNUC__ >= 7
 _Pragma("GCC diagnostic ignored \\"-Wimplicit-fallthrough\\"")
+#if __GNUC__ >= 15
+_Pragma("GCC diagnostic ignored \\"-Wzero-as-null-pointer-constant\\"")
 #endif
 %}""")
     print(f"""\