Use initalization instead of explicit zeroing

Before, we would initialize many fields twice: first
by filling the structure with zeros, and then a second
time with the real values. We can let the compiler do
the job for us, avoiding one copy.

A downside of this patch is that text gets slightly
bigger. This is because all zero() calls are effectively
inlined:

$ size build/.libs/systemd
         text    data     bss     dec     hex filename
before 897737  107300    2560 1007597   f5fed build/.libs/systemd
after  897873  107300    2560 1007733   f6075 build/.libs/systemd

… actually less than 1‰.

A few asserts that the parameter is not null had to be removed. I
don't think this changes much, because first, it is quite unlikely
for the assert to fail, and second, an immediate SEGV is almost as
good as an assert.

14 files changed, 146 insertions, 192 deletions

diff --git a/src/core/dbus-execute.c b/src/core/dbus-execute.c
index 0a53207e59..2a8a0e1ac5 100644
--- a/src/core/dbus-execute.c
+++ b/src/core/dbus-execute.c
@@ -160,9 +160,8 @@ int bus_execute_append_cpu_sched_priority(DBusMessageIter *i, const char *proper
         if (c->cpu_sched_set)
                 n = c->cpu_sched_priority;
         else {
-                struct sched_param p;
+                struct sched_param p = {};
 
-                zero(p);
                 if (sched_getparam(0, &p) >= 0)
                         n = p.sched_priority;
                 else
@@ -280,9 +279,8 @@ int bus_execute_append_rlimits(DBusMessageIter *i, const char *property, void *d
         if (c->rlimit[r])
                 u = (uint64_t) c->rlimit[r]->rlim_max;
         else {
-                struct rlimit rl;
+                struct rlimit rl = {};
 
-                zero(rl);
                 getrlimit(r, &rl);
 
                 u = (uint64_t) rl.rlim_max;
diff --git a/src/core/dbus.c b/src/core/dbus.c
index b92c7d0b99..67ab1ae7f7 100644
--- a/src/core/dbus.c
+++ b/src/core/dbus.c
@@ -203,13 +203,11 @@ static void bus_toggle_watch(DBusWatch *bus_watch, void *data) {
 }
 
 static int bus_timeout_arm(Manager *m, Watch *w) {
-        struct itimerspec its;
+        struct itimerspec its = {};
 
         assert(m);
         assert(w);
 
-        zero(its);
-
         if (dbus_timeout_get_enabled(w->data.bus_timeout)) {
                 timespec_store(&its.it_value, dbus_timeout_get_interval(w->data.bus_timeout) * USEC_PER_MSEC);
                 its.it_interval = its.it_value;
diff --git a/src/core/device.c b/src/core/device.c
index 0b01718ad4..fb948688b6 100644
--- a/src/core/device.c
+++ b/src/core/device.c
@@ -477,7 +477,6 @@ static void device_shutdown(Manager *m) {
 }
 
 static int device_enumerate(Manager *m) {
-        struct epoll_event ev;
         int r;
         struct udev_enumerate *e = NULL;
         struct udev_list_entry *item = NULL, *first = NULL;
@@ -485,6 +484,8 @@ static int device_enumerate(Manager *m) {
         assert(m);
 
         if (!m->udev) {
+                struct epoll_event ev;
+
                 if (!(m->udev = udev_new()))
                         return -ENOMEM;
 
diff --git a/src/core/execute.c b/src/core/execute.c
index 2c13d1f9f6..c51049767d 100644
--- a/src/core/execute.c
+++ b/src/core/execute.c
@@ -205,7 +205,10 @@ static int open_null_as(int flags, int nfd) {
 
 static int connect_logger_as(const ExecContext *context, ExecOutput output, const char *ident, const char *unit_id, int nfd) {
         int fd, r;
-        union sockaddr_union sa;
+        union sockaddr_union sa = {
+                .un.sun_family = AF_UNIX,
+                .un.sun_path = "/run/systemd/journal/stdout",
+        };
 
         assert(context);
         assert(output < _EXEC_OUTPUT_MAX);
@@ -216,10 +219,6 @@ static int connect_logger_as(const ExecContext *context, ExecOutput output, cons
         if (fd < 0)
                 return -errno;
 
-        zero(sa);
-        sa.un.sun_family = AF_UNIX;
-        strncpy(sa.un.sun_path, "/run/systemd/journal/stdout", sizeof(sa.un.sun_path));
-
         r = connect(fd, &sa.sa, offsetof(struct sockaddr_un, sun_path) + strlen(sa.un.sun_path));
         if (r < 0) {
                 close_nointr_nofail(fd);
@@ -938,7 +937,7 @@ static int apply_seccomp(uint32_t *syscall_filter) {
         int i;
         unsigned n;
         struct sock_filter *f;
-        struct sock_fprog prog;
+        struct sock_fprog prog = {};
 
         assert(syscall_filter);
 
@@ -970,7 +969,6 @@ static int apply_seccomp(uint32_t *syscall_filter) {
         memcpy(f + (ELEMENTSOF(header) + 2*n), footer, sizeof(footer));
 
         /* Third: install the filter */
-        zero(prog);
         prog.len = ELEMENTSOF(header) + ELEMENTSOF(footer) + 2*n;
         prog.filter = f;
         if (prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog) < 0)
@@ -1210,10 +1208,9 @@ int exec_spawn(ExecCommand *command,
                         }
 
                 if (context->cpu_sched_set) {
-                        struct sched_param param;
-
-                        zero(param);
-                        param.sched_priority = context->cpu_sched_priority;
+                        struct sched_param param = {
+                                .sched_priority = context->cpu_sched_priority,
+                        };
 
                         r = sched_setscheduler(0,
                                                context->cpu_sched_policy |
@@ -1701,7 +1698,7 @@ int exec_context_load_environment(const ExecContext *c, char ***l) {
                 int k;
                 bool ignore = false;
                 char **p;
-                glob_t pglob;
+                glob_t pglob = {};
                 int count, n;
 
                 fn = *i;
@@ -1721,7 +1718,6 @@ int exec_context_load_environment(const ExecContext *c, char ***l) {
                 }
 
                 /* Filename supports globbing, take all matching files */
-                zero(pglob);
                 errno = 0;
                 if (glob(fn, 0, NULL, &pglob) != 0) {
                         globfree(&pglob);
diff --git a/src/core/job.c b/src/core/job.c
index d5b7987a00..af5855b71d 100644
--- a/src/core/job.c
+++ b/src/core/job.c
@@ -858,10 +858,12 @@ finish:
 }
 
 int job_start_timer(Job *j) {
-        struct itimerspec its;
-        struct epoll_event ev;
+        struct itimerspec its = {};
+        struct epoll_event ev = {
+                .data.ptr = &j->timer_watch,
+                .events = EPOLLIN,
+        };
         int fd, r;
-        assert(j);
 
         if (j->unit->job_timeout <= 0 ||
             j->timer_watch.type == WATCH_JOB_TIMER)
@@ -874,7 +876,6 @@ int job_start_timer(Job *j) {
                 goto fail;
         }
 
-        zero(its);
         timespec_store(&its.it_value, j->unit->job_timeout);
 
         if (timerfd_settime(fd, 0, &its, NULL) < 0) {
@@ -882,10 +883,6 @@ int job_start_timer(Job *j) {
                 goto fail;
         }
 
-        zero(ev);
-        ev.data.ptr = &j->timer_watch;
-        ev.events = EPOLLIN;
-
         if (epoll_ctl(j->manager->epoll_fd, EPOLL_CTL_ADD, fd, &ev) < 0) {
                 r = -errno;
                 goto fail;
@@ -1064,15 +1061,14 @@ int job_deserialize(Job *j, FILE *f, FDSet *fds) {
 }
 
 int job_coldplug(Job *j) {
-        struct epoll_event ev;
+        struct epoll_event ev = {
+                .data.ptr = &j->timer_watch,
+                .events = EPOLLIN,
+        };
 
         if (j->timer_watch.type != WATCH_JOB_TIMER)
                 return 0;
 
-        zero(ev);
-        ev.data.ptr = &j->timer_watch;
-        ev.events = EPOLLIN;
-
         if (epoll_ctl(j->manager->epoll_fd, EPOLL_CTL_ADD, j->timer_watch.fd, &ev) < 0)
                 return -errno;
 
diff --git a/src/core/locale-setup.c b/src/core/locale-setup.c
index eefb256ac5..d7113b9795 100644
--- a/src/core/locale-setup.c
+++ b/src/core/locale-setup.c
@@ -68,11 +68,9 @@ static const char * const variable_names[_VARIABLE_MAX] = {
 };
 
 int locale_setup(void) {
-        char *variables[_VARIABLE_MAX];
+        char *variables[_VARIABLE_MAX] = {};
         int r = 0, i;
 
-        zero(variables);
-
         if (detect_container(NULL) <= 0) {
                 r = parse_env_file("/proc/cmdline", WHITESPACE,
                                    "locale.LANG",              &variables[VARIABLE_LANG],
diff --git a/src/core/loopback-setup.c b/src/core/loopback-setup.c
index bfd0d93204..f98a29806e 100644
--- a/src/core/loopback-setup.c
+++ b/src/core/loopback-setup.c
@@ -88,25 +88,26 @@ static int add_adresses(int fd, int if_loopback, unsigned *requests) {
         union {
                 struct sockaddr sa;
                 struct sockaddr_nl nl;
-        } sa;
+        } sa = {
+                .nl.nl_family = AF_NETLINK,
+        };
+
         union {
                 struct nlmsghdr header;
                 uint8_t buf[NLMSG_ALIGN(sizeof(struct nlmsghdr)) +
                             NLMSG_ALIGN(sizeof(struct ifaddrmsg)) +
                             RTA_LENGTH(sizeof(struct in6_addr))];
-        } request;
+        } request = {
+                .header.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifaddrmsg)),
+                .header.nlmsg_type = RTM_NEWADDR,
+                .header.nlmsg_flags = NLM_F_REQUEST|NLM_F_CREATE|NLM_F_ACK,
+                .header.nlmsg_seq = *requests + 1,
+        };
 
         struct ifaddrmsg *ifaddrmsg;
         uint32_t ipv4_address = htonl(INADDR_LOOPBACK);
         int r;
 
-        zero(request);
-
-        request.header.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifaddrmsg));
-        request.header.nlmsg_type = RTM_NEWADDR;
-        request.header.nlmsg_flags = NLM_F_REQUEST|NLM_F_CREATE|NLM_F_ACK;
-        request.header.nlmsg_seq = *requests + 1;
-
         ifaddrmsg = NLMSG_DATA(&request.header);
         ifaddrmsg->ifa_family = AF_INET;
         ifaddrmsg->ifa_prefixlen = 8;
@@ -114,13 +115,11 @@ static int add_adresses(int fd, int if_loopback, unsigned *requests) {
         ifaddrmsg->ifa_scope = RT_SCOPE_HOST;
         ifaddrmsg->ifa_index = if_loopback;
 
-        r = add_rtattr(&request.header, sizeof(request), IFA_LOCAL, &ipv4_address, sizeof(ipv4_address));
+        r = add_rtattr(&request.header, sizeof(request), IFA_LOCAL,
+                       &ipv4_address, sizeof(ipv4_address));
         if (r < 0)
                 return r;
 
-        zero(sa);
-        sa.nl.nl_family = AF_NETLINK;
-
         if (sendto_loop(fd, &request, request.header.nlmsg_len, 0, &sa.sa, sizeof(sa)) < 0)
                 return -errno;
         (*requests)++;
@@ -134,7 +133,8 @@ static int add_adresses(int fd, int if_loopback, unsigned *requests) {
         ifaddrmsg->ifa_family = AF_INET6;
         ifaddrmsg->ifa_prefixlen = 128;
 
-        r = add_rtattr(&request.header, sizeof(request), IFA_LOCAL, &in6addr_loopback, sizeof(in6addr_loopback));
+        r = add_rtattr(&request.header, sizeof(request), IFA_LOCAL,
+                       &in6addr_loopback, sizeof(in6addr_loopback));
         if (r < 0)
                 return r;
 
@@ -149,31 +149,29 @@ static int start_interface(int fd, int if_loopback, unsigned *requests) {
         union {
                 struct sockaddr sa;
                 struct sockaddr_nl nl;
-        } sa;
+        } sa = {
+                .nl.nl_family = AF_NETLINK,
+        };
+
         union {
                 struct nlmsghdr header;
                 uint8_t buf[NLMSG_ALIGN(sizeof(struct nlmsghdr)) +
                             NLMSG_ALIGN(sizeof(struct ifinfomsg))];
-        } request;
+        } request = {
+                .header.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg)),
+                .header.nlmsg_type = RTM_NEWLINK,
+                .header.nlmsg_flags = NLM_F_REQUEST|NLM_F_ACK,
+                .header.nlmsg_seq = *requests + 1,
+        };
 
         struct ifinfomsg *ifinfomsg;
 
-        zero(request);
-
-        request.header.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg));
-        request.header.nlmsg_type = RTM_NEWLINK;
-        request.header.nlmsg_flags = NLM_F_REQUEST|NLM_F_ACK;
-        request.header.nlmsg_seq = *requests + 1;
-
         ifinfomsg = NLMSG_DATA(&request.header);
         ifinfomsg->ifi_family = AF_UNSPEC;
         ifinfomsg->ifi_index = if_loopback;
         ifinfomsg->ifi_flags = IFF_UP;
         ifinfomsg->ifi_change = IFF_UP;
 
-        zero(sa);
-        sa.nl.nl_family = AF_NETLINK;
-
         if (sendto_loop(fd, &request, request.header.nlmsg_len, 0, &sa.sa, sizeof(sa)) < 0)
                 return -errno;
 
@@ -234,7 +232,10 @@ static int check_loopback(void) {
         union {
                 struct sockaddr sa;
                 struct sockaddr_in in;
-        } sa;
+        } sa = {
+                .in.sin_family = AF_INET,
+                .in.sin_addr.s_addr = INADDR_LOOPBACK,
+        };
 
         /* If we failed to set up the loop back device, check whether
          * it might already be set up */
@@ -243,10 +244,6 @@ static int check_loopback(void) {
         if (fd < 0)
                 return -errno;
 
-        zero(sa);
-        sa.in.sin_family = AF_INET;
-        sa.in.sin_addr.s_addr = INADDR_LOOPBACK;
-
         if (bind(fd, &sa.sa, sizeof(sa.in)) >= 0)
                 r = 1;
         else
@@ -260,7 +257,9 @@ int loopback_setup(void) {
         union {
                 struct sockaddr sa;
                 struct sockaddr_nl nl;
-        } sa;
+        } sa = {
+                .nl.nl_family = AF_NETLINK,
+        };
         unsigned requests = 0, i;
         int _cleanup_close_ fd = -1;
         bool eperm = false;
@@ -274,8 +273,6 @@ int loopback_setup(void) {
         if (fd < 0)
                 return -errno;
 
-        zero(sa);
-        sa.nl.nl_family = AF_NETLINK;
         if (bind(fd, &sa.sa, sizeof(sa)) < 0) {
                 r = -errno;
                 goto error;
diff --git a/src/core/main.c b/src/core/main.c
index 92f066c707..4d21dd97a3 100644
--- a/src/core/main.c
+++ b/src/core/main.c
@@ -107,13 +107,13 @@ _noreturn_ static void crash(int sig) {
         if (!arg_dump_core)
                 log_error("Caught <%s>, not dumping core.", signal_to_string(sig));
         else {
-                struct sigaction sa;
+                struct sigaction sa = {
+                        .sa_handler = nop_handler,
+                        .sa_flags = SA_NOCLDSTOP|SA_RESTART,
+                };
                 pid_t pid;
 
                 /* We want to wait for the core process, hence let's enable SIGCHLD */
-                zero(sa);
-                sa.sa_handler = nop_handler;
-                sa.sa_flags = SA_NOCLDSTOP|SA_RESTART;
                 assert_se(sigaction(SIGCHLD, &sa, NULL) == 0);
 
                 pid = fork();
@@ -121,7 +121,7 @@ _noreturn_ static void crash(int sig) {
                         log_error("Caught <%s>, cannot fork for core dump: %s", signal_to_string(sig), strerror(errno));
 
                 else if (pid == 0) {
-                        struct rlimit rl;
+                        struct rlimit rl = {};
 
                         /* Enable default signal handler for core dump */
                         zero(sa);
@@ -129,7 +129,6 @@ _noreturn_ static void crash(int sig) {
                         assert_se(sigaction(sig, &sa, NULL) == 0);
 
                         /* Don't limit the core dump size */
-                        zero(rl);
                         rl.rlim_cur = RLIM_INFINITY;
                         rl.rlim_max = RLIM_INFINITY;
                         setrlimit(RLIMIT_CORE, &rl);
@@ -162,16 +161,16 @@ _noreturn_ static void crash(int sig) {
                 chvt(arg_crash_chvt);
 
         if (arg_crash_shell) {
-                struct sigaction sa;
+                struct sigaction sa = {
+                        .sa_handler = SIG_IGN,
+                        .sa_flags = SA_NOCLDSTOP|SA_NOCLDWAIT|SA_RESTART,
+                };
                 pid_t pid;
 
                 log_info("Executing crash shell in 10s...");
                 sleep(10);
 
                 /* Let the kernel reap children for us */
-                zero(sa);
-                sa.sa_handler = SIG_IGN;
-                sa.sa_flags = SA_NOCLDSTOP|SA_NOCLDWAIT|SA_RESTART;
                 assert_se(sigaction(SIGCHLD, &sa, NULL) == 0);
 
                 pid = fork();
@@ -193,12 +192,10 @@ _noreturn_ static void crash(int sig) {
 }
 
 static void install_crash_handler(void) {
-        struct sigaction sa;
-
-        zero(sa);
-
-        sa.sa_handler = crash;
-        sa.sa_flags = SA_NODEFER;
+        struct sigaction sa = {
+                .sa_handler = crash,
+                .sa_flags = SA_NODEFER,
+        };
 
         sigaction_many(&sa, SIGNALS_CRASH_HANDLER, -1);
 }
diff --git a/src/core/manager.c b/src/core/manager.c
index e26522a4dd..549153e057 100644
--- a/src/core/manager.c
+++ b/src/core/manager.c
@@ -93,12 +93,15 @@ static int manager_setup_notify(Manager *m) {
         union {
                 struct sockaddr sa;
                 struct sockaddr_un un;
-        } sa;
-        struct epoll_event ev;
+        } sa = {
+                .sa.sa_family = AF_UNIX,
+        };
+        struct epoll_event ev = {
+                .events = EPOLLIN,
+                .data.ptr = &m->notify_watch,
+        };
         int one = 1, r;
 
-        assert(m);
-
         m->notify_watch.type = WATCH_NOTIFY;
         m->notify_watch.fd = socket(AF_UNIX, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
         if (m->notify_watch.fd < 0) {
@@ -106,9 +109,6 @@ static int manager_setup_notify(Manager *m) {
                 return -errno;
         }
 
-        zero(sa);
-        sa.sa.sa_family = AF_UNIX;
-
         if (getpid() != 1 || detect_container(NULL) > 0)
                 snprintf(sa.un.sun_path, sizeof(sa.un.sun_path), NOTIFY_SOCKET "/%llu", random_ull());
         else
@@ -129,10 +129,6 @@ static int manager_setup_notify(Manager *m) {
                 return -errno;
         }
 
-        zero(ev);
-        ev.events = EPOLLIN;
-        ev.data.ptr = &m->notify_watch;
-
         r = epoll_ctl(m->epoll_fd, EPOLL_CTL_ADD, m->notify_watch.fd, &ev);
         if (r < 0) {
                 log_error("Failed to add notification socket fd to epoll: %m");
@@ -150,16 +146,14 @@ static int manager_setup_notify(Manager *m) {
 }
 
 static int manager_jobs_in_progress_mod_timer(Manager *m) {
-        struct itimerspec its;
+        struct itimerspec its = {
+                .it_value.tv_sec = JOBS_IN_PROGRESS_WAIT_SEC,
+                .it_interval.tv_sec = JOBS_IN_PROGRESS_PERIOD_SEC,
+        };
 
         if (m->jobs_in_progress_watch.type != WATCH_JOBS_IN_PROGRESS)
                 return 0;
 
-        zero(its);
-
-        its.it_value.tv_sec = JOBS_IN_PROGRESS_WAIT_SEC;
-        its.it_interval.tv_sec = JOBS_IN_PROGRESS_PERIOD_SEC;
-
         if (timerfd_settime(m->jobs_in_progress_watch.fd, 0, &its, NULL) < 0)
                 return -errno;
 
@@ -167,11 +161,12 @@ static int manager_jobs_in_progress_mod_timer(Manager *m) {
 }
 
 static int manager_watch_jobs_in_progress(Manager *m) {
-        struct epoll_event ev;
+        struct epoll_event ev = {
+                .events = EPOLLIN,
+                .data.ptr = &m->jobs_in_progress_watch,
+        };
         int r;
 
-        assert(m);
-
         if (m->jobs_in_progress_watch.type != WATCH_INVALID)
                 return 0;
 
@@ -189,10 +184,6 @@ static int manager_watch_jobs_in_progress(Manager *m) {
                 goto err;
         }
 
-        zero(ev);
-        ev.events = EPOLLIN;
-        ev.data.ptr = &m->jobs_in_progress_watch;
-
         if (epoll_ctl(m->epoll_fd, EPOLL_CTL_ADD, m->jobs_in_progress_watch.fd, &ev) < 0) {
                 log_error("Failed to add jobs progress timer fd to epoll: %m");
                 r = -errno;
@@ -287,10 +278,18 @@ static void manager_print_jobs_in_progress(Manager *m) {
 }
 
 static int manager_setup_time_change(Manager *m) {
-        struct epoll_event ev;
-        struct itimerspec its;
+        struct epoll_event ev = {
+                .events = EPOLLIN,
+                .data.ptr = &m->time_change_watch,
+        };
+
+        /* We only care for the cancellation event, hence we set the
+         * timeout to the latest possible value. */
+        struct itimerspec its = {
+                .it_value.tv_sec = TIME_T_MAX,
+        };
+        assert_cc(sizeof(time_t) == sizeof(TIME_T_MAX));
 
-        assert(m);
         assert(m->time_change_watch.type == WATCH_INVALID);
 
         /* Uses TFD_TIMER_CANCEL_ON_SET to get notifications whenever
@@ -303,13 +302,6 @@ static int manager_setup_time_change(Manager *m) {
                 return -errno;
         }
 
-        zero(its);
-
-        /* We only care for the cancellation event, hence we set the
-         * timeout to the latest possible value. */
-        assert_cc(sizeof(time_t) == sizeof(TIME_T_MAX));
-        its.it_value.tv_sec = TIME_T_MAX;
-
         if (timerfd_settime(m->time_change_watch.fd, TFD_TIMER_ABSTIME|TFD_TIMER_CANCEL_ON_SET, &its, NULL) < 0) {
                 log_debug("Failed to set up TFD_TIMER_CANCEL_ON_SET, ignoring: %m");
                 close_nointr_nofail(m->time_change_watch.fd);
@@ -317,10 +309,6 @@ static int manager_setup_time_change(Manager *m) {
                 return 0;
         }
 
-        zero(ev);
-        ev.events = EPOLLIN;
-        ev.data.ptr = &m->time_change_watch;
-
         if (epoll_ctl(m->epoll_fd, EPOLL_CTL_ADD, m->time_change_watch.fd, &ev) < 0) {
                 log_error("Failed to add timer change fd to epoll: %m");
                 return -errno;
@@ -360,15 +348,18 @@ static int enable_special_signals(Manager *m) {
 
 static int manager_setup_signals(Manager *m) {
         sigset_t mask;
-        struct epoll_event ev;
-        struct sigaction sa;
+        struct epoll_event ev = {
+                .events = EPOLLIN,
+                .data.ptr = &m->signal_watch,
+        };
+        struct sigaction sa = {
+                .sa_handler = SIG_DFL,
+                .sa_flags = SA_NOCLDSTOP|SA_RESTART,
+        };
 
         assert(m);
 
         /* We are not interested in SIGSTOP and friends. */
-        zero(sa);
-        sa.sa_handler = SIG_DFL;
-        sa.sa_flags = SA_NOCLDSTOP|SA_RESTART;
         assert_se(sigaction(SIGCHLD, &sa, NULL) == 0);
 
         assert_se(sigemptyset(&mask) == 0);
@@ -410,10 +401,6 @@ static int manager_setup_signals(Manager *m) {
         if (m->signal_watch.fd < 0)
                 return -errno;
 
-        zero(ev);
-        ev.events = EPOLLIN;
-        ev.data.ptr = &m->signal_watch;
-
         if (epoll_ctl(m->epoll_fd, EPOLL_CTL_ADD, m->signal_watch.fd, &ev) < 0)
                 return -errno;
 
@@ -1184,30 +1171,29 @@ static int manager_process_notify_fd(Manager *m) {
 
         for (;;) {
                 char buf[4096];
-                struct msghdr msghdr;
-                struct iovec iovec;
-                struct ucred *ucred;
+                struct iovec iovec = {
+                        .iov_base = buf,
+                        .iov_len = sizeof(buf)-1,
+                };
+
                 union {
                         struct cmsghdr cmsghdr;
                         uint8_t buf[CMSG_SPACE(sizeof(struct ucred))];
-                } control;
+                } control = {};
+
+                struct msghdr msghdr = {
+                        .msg_iov = &iovec,
+                        .msg_iovlen = 1,
+                        .msg_control = &control,
+                        .msg_controllen = sizeof(control),
+                };
+                struct ucred *ucred;
                 Unit *u;
                 char _cleanup_strv_free_ **tags = NULL;
 
-                zero(iovec);
-                iovec.iov_base = buf;
-                iovec.iov_len = sizeof(buf)-1;
-
-                zero(control);
-                zero(msghdr);
-                msghdr.msg_iov = &iovec;
-                msghdr.msg_iovlen = 1;
-                msghdr.msg_control = &control;
-                msghdr.msg_controllen = sizeof(control);
-
                 n = recvmsg(m->notify_watch.fd, &msghdr, MSG_DONTWAIT);
                 if (n <= 0) {
-                        if (n >= 0)
+                        if (n == 0)
                                 return -EIO;
 
                         if (errno == EAGAIN || errno == EINTR)
@@ -1254,12 +1240,10 @@ static int manager_dispatch_sigchld(Manager *m) {
         assert(m);
 
         for (;;) {
-                siginfo_t si;
+                siginfo_t si = {};
                 Unit *u;
                 int r;
 
-                zero(si);
-
                 /* First we call waitd() for a PID and do not reap the
                  * zombie. That way we can still access /proc/$PID for
                  * it while it is a zombie. */
diff --git a/src/core/mount.c b/src/core/mount.c
index 51a81a9488..4f245555f2 100644
--- a/src/core/mount.c
+++ b/src/core/mount.c
@@ -293,7 +293,7 @@ static int mount_add_requires_mounts_links(Mount *m) {
 }
 
 static char* mount_test_option(const char *haystack, const char *needle) {
-        struct mntent me;
+        struct mntent me = { .mnt_opts = (char*) haystack };
 
         assert(needle);
 
@@ -303,9 +303,6 @@ static char* mount_test_option(const char *haystack, const char *needle) {
         if (!haystack)
                 return NULL;
 
-        zero(me);
-        me.mnt_opts = (char*) haystack;
-
         return hasmntopt(&me, needle);
 }
 
@@ -1706,10 +1703,14 @@ static void mount_shutdown(Manager *m) {
 
 static int mount_enumerate(Manager *m) {
         int r;
-        struct epoll_event ev;
         assert(m);
 
         if (!m->proc_self_mountinfo) {
+                struct epoll_event ev = {
+                        .events = EPOLLPRI,
+                        .data.ptr = &m->mount_watch,
+                };
+
                 m->proc_self_mountinfo = fopen("/proc/self/mountinfo", "re");
                 if (!m->proc_self_mountinfo)
                         return -errno;
@@ -1717,10 +1718,6 @@ static int mount_enumerate(Manager *m) {
                 m->mount_watch.type = WATCH_MOUNT;
                 m->mount_watch.fd = fileno(m->proc_self_mountinfo);
 
-                zero(ev);
-                ev.events = EPOLLPRI;
-                ev.data.ptr = &m->mount_watch;
-
                 if (epoll_ctl(m->epoll_fd, EPOLL_CTL_ADD, m->mount_watch.fd, &ev) < 0)
                         return -errno;
         }
diff --git a/src/core/service.c b/src/core/service.c
index 98266a5a90..a104b300c3 100644
--- a/src/core/service.c
+++ b/src/core/service.c
@@ -3446,7 +3446,7 @@ static int service_enumerate(Manager *m) {
         unsigned i;
         DIR _cleanup_closedir_ *d = NULL;
         char _cleanup_free_ *path = NULL, *fpath = NULL, *name = NULL;
-        Set *runlevel_services[ELEMENTSOF(rcnd_table)];
+        Set *runlevel_services[ELEMENTSOF(rcnd_table)] = {};
         Set _cleanup_set_free_ *shutdown_services = NULL;
         Unit *service;
         Iterator j;
@@ -3457,8 +3457,6 @@ static int service_enumerate(Manager *m) {
         if (m->running_as != SYSTEMD_SYSTEM)
                 return 0;
 
-        zero(runlevel_services);
-
         STRV_FOREACH(p, m->lookup_paths.sysvrcnd_path)
                 for (i = 0; i < ELEMENTSOF(rcnd_table); i ++) {
                         struct dirent *de;
diff --git a/src/core/swap.c b/src/core/swap.c
index dc98f47387..b363c5ec09 100644
--- a/src/core/swap.c
+++ b/src/core/swap.c
@@ -1242,10 +1242,14 @@ static void swap_shutdown(Manager *m) {
 
 static int swap_enumerate(Manager *m) {
         int r;
-        struct epoll_event ev;
         assert(m);
 
         if (!m->proc_swaps) {
+                struct epoll_event ev = {
+                        .events = EPOLLPRI,
+                        .data.ptr = &m->swap_watch,
+                };
+
                 m->proc_swaps = fopen("/proc/swaps", "re");
                 if (!m->proc_swaps)
                         return (errno == ENOENT) ? 0 : -errno;
@@ -1253,10 +1257,6 @@ static int swap_enumerate(Manager *m) {
                 m->swap_watch.type = WATCH_SWAP;
                 m->swap_watch.fd = fileno(m->proc_swaps);
 
-                zero(ev);
-                ev.events = EPOLLPRI;
-                ev.data.ptr = &m->swap_watch;
-
                 if (epoll_ctl(m->epoll_fd, EPOLL_CTL_ADD, m->swap_watch.fd, &ev) < 0)
                         return -errno;
         }
diff --git a/src/core/umount.c b/src/core/umount.c
index 95e47e3c5a..8c69e74caf 100644
--- a/src/core/umount.c
+++ b/src/core/umount.c
@@ -381,7 +381,13 @@ static int delete_loopback(const char *device) {
 static int delete_dm(dev_t devnum) {
         int _cleanup_close_ fd = -1;
         int r;
-        struct dm_ioctl dm;
+        struct dm_ioctl dm = {
+                .version = {DM_VERSION_MAJOR,
+                            DM_VERSION_MINOR,
+                            DM_VERSION_PATCHLEVEL},
+                .data_size = sizeof(dm),
+                .dev = devnum,
+        };
 
         assert(major(devnum) != 0);
 
@@ -389,14 +395,6 @@ static int delete_dm(dev_t devnum) {
         if (fd < 0)
                 return -errno;
 
-        zero(dm);
-        dm.version[0] = DM_VERSION_MAJOR;
-        dm.version[1] = DM_VERSION_MINOR;
-        dm.version[2] = DM_VERSION_PATCHLEVEL;
-
-        dm.data_size = sizeof(dm);
-        dm.dev = devnum;
-
         r = ioctl(fd, DM_DEV_REMOVE, &dm);
         return r >= 0 ? 0 : -errno;
 }
diff --git a/src/core/unit.c b/src/core/unit.c
index dbb1882965..63e42b2330 100644
--- a/src/core/unit.c
+++ b/src/core/unit.c
@@ -1520,17 +1520,16 @@ void unit_notify(Unit *u, UnitActiveState os, UnitActiveState ns, bool reload_su
 }
 
 int unit_watch_fd(Unit *u, int fd, uint32_t events, Watch *w) {
-        struct epoll_event ev;
+        struct epoll_event ev = {
+                .data.ptr = w,
+                .events = events,
+        };
 
         assert(u);
         assert(fd >= 0);
         assert(w);
         assert(w->type == WATCH_INVALID || (w->type == WATCH_FD && w->fd == fd && w->data.unit == u));
 
-        zero(ev);
-        ev.data.ptr = w;
-        ev.events = events;
-
         if (epoll_ctl(u->manager->epoll_fd,
                       w->type == WATCH_INVALID ? EPOLL_CTL_ADD : EPOLL_CTL_MOD,
                       fd,
@@ -1578,7 +1577,7 @@ void unit_unwatch_pid(Unit *u, pid_t pid) {
 }
 
 int unit_watch_timer(Unit *u, clockid_t clock_id, bool relative, usec_t usec, Watch *w) {
-        struct itimerspec its;
+        struct itimerspec its = {};
         int flags, fd;
         bool ours;
 
@@ -1603,8 +1602,6 @@ int unit_watch_timer(Unit *u, clockid_t clock_id, bool relative, usec_t usec, Wa
         } else
                 assert_not_reached("Invalid watch type");
 
-        zero(its);
-
         if (usec <= 0) {
                 /* Set absolute time in the past, but not 0, since we
                  * don't want to disarm the timer */
@@ -1622,11 +1619,10 @@ int unit_watch_timer(Unit *u, clockid_t clock_id, bool relative, usec_t usec, Wa
                 goto fail;
 
         if (w->type == WATCH_INVALID) {
-                struct epoll_event ev;
-
-                zero(ev);
-                ev.data.ptr = w;
-                ev.events = EPOLLIN;
+                struct epoll_event ev = {
+                        .data.ptr = w,
+                        .events = EPOLLIN,
+                };
 
                 if (epoll_ctl(u->manager->epoll_fd, EPOLL_CTL_ADD, fd, &ev) < 0)
                         goto fail;