fix: add missing fflush(stdout) to write log message immediately (try 2)

[lark]

Without fflush(stdout), log messages have incorrect timestamp (added by syslogd or journald), or even get printed out when exit() but not startup.

Refactor to align on format of status_shared->log_entries[n].message (newline included)

[lark]

please review carefully as it's not easy to make it right.

[stackia]

LGTM but I don't have much time recently to test against your change.

I'll just merge and will do some testing when I'm free.

[lark]

truncation is not handled well on the last attempt. this patch should be solid. you can integrate it with other fixes.
the key difference is not looking at format string but result string buffer. (for too long string, '\n' at the end in the format won't be honored.)

As I mentioned, it's not easy to make it right.

diff --git a/src/utils.c b/src/utils.c
index 0dfe94a..5a793da 100644
--- a/src/utils.c
+++ b/src/utils.c
@@ -117,11 +117,10 @@ int logger(loglevel_t level, const char *format, ...) {
     if (r < 0)
       return r;

-    /* Automatically add newline if format doesn't end with one */
-    if (format && strlen(format) > 0 && format[strlen(format) - 1] != '\n') {
-      if (r > (int)sizeof(message) - prefix_len - 2)
-        r = (int)sizeof(message) - prefix_len - 2;
-
+    /* Make sure newline ended, assuming r > 0 (format shouldn't be empty string "") */
+    if (r >= (int)sizeof(message) - prefix_len - 1)
+      message[sizeof(message) - 2] = '\n';
+    else if (message[prefix_len + r - 1] != '\n' ) {
       message[prefix_len + r++] = '\n';
       message[prefix_len + r] = '\0';
     }