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, 7 insertions, 9 deletions

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;
 }