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.

1 files changed, 6 insertions, 12 deletions

diff --git a/src/shared/utmp-wtmp.c b/src/shared/utmp-wtmp.c
index 3494b56908..5ee3d22e71 100644
--- a/src/shared/utmp-wtmp.c
+++ b/src/shared/utmp-wtmp.c
@@ -33,7 +33,7 @@
 #include "utmp-wtmp.h"
 
 int utmp_get_runlevel(int *runlevel, int *previous) {
-        struct utmpx lookup, *found;
+        struct utmpx *found, lookup = { .ut_type = RUN_LVL };
         int r;
         const char *e;
 
@@ -66,9 +66,6 @@ int utmp_get_runlevel(int *runlevel, int *previous) {
 
         setutxent();
 
-        zero(lookup);
-        lookup.ut_type = RUN_LVL;
-
         if (!(found = getutxid(&lookup)))
                 r = -errno;
         else {
@@ -102,14 +99,12 @@ static void init_timestamp(struct utmpx *store, usec_t t) {
 }
 
 static void init_entry(struct utmpx *store, usec_t t) {
-        struct utsname uts;
+        struct utsname uts = {};
 
         assert(store);
 
         init_timestamp(store, t);
 
-        zero(uts);
-
         if (uname(&uts) >= 0)
                 strncpy(store->ut_host, uts.release, sizeof(store->ut_host));
 
@@ -311,7 +306,10 @@ static int write_to_terminal(const char *tty, const char *message) {
 
         while (left > 0) {
                 ssize_t n;
-                struct pollfd pollfd;
+                struct pollfd pollfd = {
+                        .fd = fd,
+                        .events = POLLOUT,
+                };
                 usec_t t;
                 int k;
 
@@ -320,10 +318,6 @@ static int write_to_terminal(const char *tty, const char *message) {
                 if (t >= end)
                         return -ETIME;
 
-                zero(pollfd);
-                pollfd.fd = fd;
-                pollfd.events = POLLOUT;
-
                 k = poll(&pollfd, 1, (end - t) / USEC_PER_MSEC);
                 if (k < 0)
                         return -errno;