core,logind,systemctl,journald: replace calls to strerror() with setting errno + %m

strerror() is not thread safe and calling it just isn't worth the effort
required to justify why it would be safe in those cases. It's easier to just
use %m which is thread-safe out of the box. I don't think that any of the
changes in the patch cause any functional difference. This is just about
getting rid of calls to strerror() in general.

When we print an error message and fail to format the string, using something
like "(null)" is good enough. This is very very unlikely to happen anyway.

1 files changed, 6 insertions, 10 deletions

diff --git a/src/core/cgroup.c b/src/core/cgroup.c
index 6d40faa48b..bbd107849c 100644
--- a/src/core/cgroup.c
+++ b/src/core/cgroup.c
@@ -398,17 +398,13 @@ static char *format_cgroup_memory_limit_comparison(char *buf, size_t l, Unit *u,
          * In the absence of reliably being able to detect whether memcg swap support is available or not,
          * only complain if the error is not ENOENT. */
         if (r > 0 || IN_SET(r, -ENODATA, -EOWNERDEAD) ||
-            (r == -ENOENT && streq(property_name, "MemorySwapMax"))) {
+            (r == -ENOENT && streq(property_name, "MemorySwapMax")))
                 buf[0] = 0;
-                return buf;
-        }
-
-        if (r < 0) {
-                (void) snprintf(buf, l, " (error getting kernel value: %s)", strerror_safe(r));
-                return buf;
-        }
-
-        (void) snprintf(buf, l, " (different value in kernel: %" PRIu64 ")", kval);
+        else if (r < 0) {
+                errno = -r;
+                (void) snprintf(buf, l, " (error getting kernel value: %m)");
+        } else
+                (void) snprintf(buf, l, " (different value in kernel: %" PRIu64 ")", kval);
 
         return buf;
 }