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, 18 insertions, 25 deletions

diff --git a/src/shared/log.c b/src/shared/log.c
index 0dd04bc51e..876f22dfc5 100644
--- a/src/shared/log.c
+++ b/src/shared/log.c
@@ -129,16 +129,15 @@ static int create_log_socket(int type) {
 }
 
 static int log_open_syslog(void) {
-        union sockaddr_union sa;
         int r;
+        union sockaddr_union sa = {
+                .un.sun_family = AF_UNIX,
+                .un.sun_path = "/dev/log",
+        };
 
         if (syslog_fd >= 0)
                 return 0;
 
-        zero(sa);
-        sa.un.sun_family = AF_UNIX;
-        strncpy(sa.un.sun_path, "/dev/log", sizeof(sa.un.sun_path));
-
         syslog_fd = create_log_socket(SOCK_DGRAM);
         if (syslog_fd < 0) {
                 r = syslog_fd;
@@ -183,7 +182,10 @@ void log_close_journal(void) {
 }
 
 static int log_open_journal(void) {
-        union sockaddr_union sa;
+        union sockaddr_union sa = {
+                .un.sun_family = AF_UNIX,
+                .un.sun_path = "/run/systemd/journal/socket",
+        };
         int r;
 
         if (journal_fd >= 0)
@@ -195,10 +197,6 @@ static int log_open_journal(void) {
                 goto fail;
         }
 
-        zero(sa);
-        sa.un.sun_family = AF_UNIX;
-        strncpy(sa.un.sun_path, "/run/systemd/journal/socket", sizeof(sa.un.sun_path));
-
         if (connect(journal_fd, &sa.sa, offsetof(struct sockaddr_un, sun_path) + strlen(sa.un.sun_path)) < 0) {
                 r = -errno;
                 goto fail;
@@ -313,7 +311,7 @@ static int write_to_console(
                 const char *buffer) {
 
         char location[64];
-        struct iovec iovec[5];
+        struct iovec iovec[5] = {};
         unsigned n = 0;
         bool highlight;
 
@@ -322,8 +320,6 @@ static int write_to_console(
 
         highlight = LOG_PRI(level) <= LOG_ERR && show_color;
 
-        zero(iovec);
-
         if (show_location) {
                 snprintf(location, sizeof(location), "(%s:%u) ", file, line);
                 char_array_0(location);
@@ -353,8 +349,11 @@ static int write_to_syslog(
         const char *buffer) {
 
         char header_priority[16], header_time[64], header_pid[16];
-        struct iovec iovec[5];
-        struct msghdr msghdr;
+        struct iovec iovec[5] = {};
+        struct msghdr msghdr = {
+                .msg_iov = iovec,
+                .msg_iovlen = ELEMENTSOF(iovec),
+        };
         time_t t;
         struct tm *tm;
 
@@ -375,7 +374,6 @@ static int write_to_syslog(
         snprintf(header_pid, sizeof(header_pid), "[%lu]: ", (unsigned long) getpid());
         char_array_0(header_pid);
 
-        zero(iovec);
         IOVEC_SET_STRING(iovec[0], header_priority);
         IOVEC_SET_STRING(iovec[1], header_time);
         IOVEC_SET_STRING(iovec[2], program_invocation_short_name);
@@ -386,10 +384,6 @@ static int write_to_syslog(
         if (syslog_is_stream)
                 iovec[4].iov_len++;
 
-        zero(msghdr);
-        msghdr.msg_iov = iovec;
-        msghdr.msg_iovlen = ELEMENTSOF(iovec);
-
         for (;;) {
                 ssize_t n;
 
@@ -417,7 +411,7 @@ static int write_to_kmsg(
         const char *buffer) {
 
         char header_priority[16], header_pid[16];
-        struct iovec iovec[5];
+        struct iovec iovec[5] = {};
 
         if (kmsg_fd < 0)
                 return 0;
@@ -428,7 +422,6 @@ static int write_to_kmsg(
         snprintf(header_pid, sizeof(header_pid), "[%lu]: ", (unsigned long) getpid());
         char_array_0(header_pid);
 
-        zero(iovec);
         IOVEC_SET_STRING(iovec[0], header_priority);
         IOVEC_SET_STRING(iovec[1], program_invocation_short_name);
         IOVEC_SET_STRING(iovec[2], header_pid);
@@ -482,8 +475,8 @@ static int write_to_journal(
         const char *buffer) {
 
         char header[LINE_MAX];
-        struct iovec iovec[4] = {{0}};
-        struct msghdr mh = {0};
+        struct iovec iovec[4] = {};
+        struct msghdr mh = {};
 
         if (journal_fd < 0)
                 return 0;
@@ -742,7 +735,7 @@ int log_struct_internal(
             journal_fd >= 0) {
 
                 char header[LINE_MAX];
-                struct iovec iovec[17] = {{0}};
+                struct iovec iovec[17] = {};
                 unsigned n = 0, i;
                 struct msghdr mh;
                 static const char nl = '\n';