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.

5 files changed, 31 insertions, 51 deletions

diff --git a/src/login/loginctl.c b/src/login/loginctl.c
index 6c229c64e3..36c65bc8d0 100644
--- a/src/login/loginctl.c
+++ b/src/login/loginctl.c
@@ -834,17 +834,13 @@ static int show_one(const char *verb, DBusConnection *bus, const char *path, boo
         const char *interface = "";
         int r;
         DBusMessageIter iter, sub, sub2, sub3;
-        SessionStatusInfo session_info;
-        UserStatusInfo user_info;
-        SeatStatusInfo seat_info;
+        SessionStatusInfo session_info = {};
+        UserStatusInfo user_info = {};
+        SeatStatusInfo seat_info = {};
 
         assert(path);
         assert(new_line);
 
-        zero(session_info);
-        zero(user_info);
-        zero(seat_info);
-
         r = bus_method_call_with_reply(
                         bus,
                         "org.freedesktop.login1",
diff --git a/src/login/logind-inhibit.c b/src/login/logind-inhibit.c
index c43ae23acf..e77088364a 100644
--- a/src/login/logind-inhibit.c
+++ b/src/login/logind-inhibit.c
@@ -292,7 +292,7 @@ int inhibitor_create_fifo(Inhibitor *i) {
 
         /* Open reading side */
         if (i->fifo_fd < 0) {
-                struct epoll_event ev;
+                struct epoll_event ev = {};
 
                 i->fifo_fd = open(i->fifo_path, O_RDONLY|O_CLOEXEC|O_NDELAY);
                 if (i->fifo_fd < 0)
@@ -302,7 +302,6 @@ int inhibitor_create_fifo(Inhibitor *i) {
                 if (r < 0)
                         return r;
 
-                zero(ev);
                 ev.events = 0;
                 ev.data.u32 = FD_OTHER_BASE + i->fifo_fd;
 
diff --git a/src/login/logind-session.c b/src/login/logind-session.c
index 71c79127e9..97c24d094b 100644
--- a/src/login/logind-session.c
+++ b/src/login/logind-session.c
@@ -898,7 +898,7 @@ int session_create_fifo(Session *s) {
 
         /* Open reading side */
         if (s->fifo_fd < 0) {
-                struct epoll_event ev;
+                struct epoll_event ev = {};
 
                 s->fifo_fd = open(s->fifo_path, O_RDONLY|O_CLOEXEC|O_NDELAY);
                 if (s->fifo_fd < 0)
@@ -908,7 +908,6 @@ int session_create_fifo(Session *s) {
                 if (r < 0)
                         return r;
 
-                zero(ev);
                 ev.events = 0;
                 ev.data.u32 = FD_OTHER_BASE + s->fifo_fd;
 
diff --git a/src/login/logind.c b/src/login/logind.c
index f72aac5e61..c9e492fc4f 100644
--- a/src/login/logind.c
+++ b/src/login/logind.c
@@ -1174,7 +1174,10 @@ static void manager_dispatch_other(Manager *m, int fd) {
 static int manager_connect_bus(Manager *m) {
         DBusError error;
         int r;
-        struct epoll_event ev;
+        struct epoll_event ev = {
+                .events = EPOLLIN,
+                .data.u32 = FD_BUS,
+        };
 
         assert(m);
         assert(!m->bus);
@@ -1230,10 +1233,6 @@ static int manager_connect_bus(Manager *m) {
                 goto fail;
         }
 
-        zero(ev);
-        ev.events = EPOLLIN;
-        ev.data.u32 = FD_BUS;
-
         if (epoll_ctl(m->epoll_fd, EPOLL_CTL_ADD, m->bus_fd, &ev) < 0)
                 goto fail;
 
@@ -1246,7 +1245,10 @@ fail:
 }
 
 static int manager_connect_console(Manager *m) {
-        struct epoll_event ev;
+        struct epoll_event ev = {
+                .events = 0,
+                .data.u32 = FD_CONSOLE,
+        };
 
         assert(m);
         assert(m->console_active_fd < 0);
@@ -1271,10 +1273,6 @@ static int manager_connect_console(Manager *m) {
                 return -errno;
         }
 
-        zero(ev);
-        ev.events = 0;
-        ev.data.u32 = FD_CONSOLE;
-
         if (epoll_ctl(m->epoll_fd, EPOLL_CTL_ADD, m->console_active_fd, &ev) < 0)
                 return -errno;
 
@@ -1282,8 +1280,11 @@ static int manager_connect_console(Manager *m) {
 }
 
 static int manager_connect_udev(Manager *m) {
-        struct epoll_event ev;
         int r;
+        struct epoll_event ev = {
+                .events = EPOLLIN,
+                .data.u32 = FD_SEAT_UDEV,
+        };
 
         assert(m);
         assert(!m->udev_seat_monitor);
@@ -1304,9 +1305,6 @@ static int manager_connect_udev(Manager *m) {
 
         m->udev_seat_fd = udev_monitor_get_fd(m->udev_seat_monitor);
 
-        zero(ev);
-        ev.events = EPOLLIN;
-        ev.data.u32 = FD_SEAT_UDEV;
         if (epoll_ctl(m->epoll_fd, EPOLL_CTL_ADD, m->udev_seat_fd, &ev) < 0)
                 return -errno;
 
@@ -1447,7 +1445,7 @@ int manager_get_idle_hint(Manager *m, dual_timestamp *t) {
 
 int manager_dispatch_idle_action(Manager *m) {
         struct dual_timestamp since;
-        struct itimerspec its;
+        struct itimerspec its = {};
         int r;
         usec_t n;
 
@@ -1459,7 +1457,6 @@ int manager_dispatch_idle_action(Manager *m) {
                 goto finish;
         }
 
-        zero(its);
         n = now(CLOCK_MONOTONIC);
 
         r = manager_get_idle_hint(m, &since);
@@ -1482,7 +1479,10 @@ int manager_dispatch_idle_action(Manager *m) {
         }
 
         if (m->idle_action_fd < 0) {
-                struct epoll_event ev;
+                struct epoll_event ev = {
+                        .events = EPOLLIN,
+                        .data.u32 = FD_IDLE_ACTION,
+                };
 
                 m->idle_action_fd = timerfd_create(CLOCK_MONOTONIC, TFD_NONBLOCK|TFD_CLOEXEC);
                 if (m->idle_action_fd < 0) {
@@ -1491,10 +1491,6 @@ int manager_dispatch_idle_action(Manager *m) {
                         goto finish;
                 }
 
-                zero(ev);
-                ev.events = EPOLLIN;
-                ev.data.u32 = FD_IDLE_ACTION;
-
                 if (epoll_ctl(m->epoll_fd, EPOLL_CTL_ADD, m->idle_action_fd, &ev) < 0) {
                         log_error("Failed to add idle action timer to epoll: %m");
                         r = -errno;
diff --git a/src/login/pam-module.c b/src/login/pam-module.c
index 0d4f7991e7..c8f4dae77e 100644
--- a/src/login/pam-module.c
+++ b/src/login/pam-module.c
@@ -256,13 +256,15 @@ static bool check_user_lists(
 }
 
 static int get_seat_from_display(const char *display, const char **seat, uint32_t *vtnr) {
-        char *p = NULL;
+        char _cleanup_free_ *p = NULL;
         int r;
-        int fd;
-        union sockaddr_union sa;
+        int _cleanup_close_ fd = -1;
+        union sockaddr_union sa = {
+                .un.sun_family = AF_UNIX,
+        };
         struct ucred ucred;
         socklen_t l;
-        char *tty;
+        char _cleanup_free_ *tty = NULL;
         int v;
 
         assert(display);
@@ -277,27 +279,17 @@ static int get_seat_from_display(const char *display, const char **seat, uint32_
         r = socket_from_display(display, &p);
         if (r < 0)
                 return r;
+        strncpy(sa.un.sun_path, p, sizeof(sa.un.sun_path)-1);
 
         fd = socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC, 0);
-        if (fd < 0) {
-                free(p);
+        if (fd < 0)
                 return -errno;
-        }
-
-        zero(sa);
-        sa.un.sun_family = AF_UNIX;
-        strncpy(sa.un.sun_path, p, sizeof(sa.un.sun_path)-1);
-        free(p);
 
-        if (connect(fd, &sa.sa, offsetof(struct sockaddr_un, sun_path) + strlen(sa.un.sun_path)) < 0) {
-                close_nointr_nofail(fd);
+        if (connect(fd, &sa.sa, offsetof(struct sockaddr_un, sun_path) + strlen(sa.un.sun_path)) < 0)
                 return -errno;
-        }
 
         l = sizeof(ucred);
         r = getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &ucred, &l);
-        close_nointr_nofail(fd);
-
         if (r < 0)
                 return -errno;
 
@@ -306,8 +298,6 @@ static int get_seat_from_display(const char *display, const char **seat, uint32_
                 return r;
 
         v = vtnr_from_tty(tty);
-        free(tty);
-
         if (v < 0)
                 return v;
         else if (v == 0)