Add a compile-time assertion to prevent a recurrence of 31080.

src/lib/log/log.c

@@ -1275,6 +1275,8 @@ static const char *domain_list[] = {
 
 CTASSERT(ARRAY_LENGTH(domain_list) == N_LOGGING_DOMAINS + 1);
 
+CTASSERT((UINT64_C(1)<<(N_LOGGING_DOMAINS-1)) < LOWEST_RESERVED_LD_FLAG_);
+
 /** Return a bitmask for the log domain for which <b>domain</b> is the name,
  * or 0 if there is no such name. */
 static log_domain_mask_t

src/lib/log/log.h

@@ -118,6 +118,8 @@
 #define LD_MESG      (UINT64_C(1)<<29)
 #define N_LOGGING_DOMAINS 30
 
+/** First bit that is reserved in log_domain_mask_t for non-domain flags. */
+#define LOWEST_RESERVED_LD_FLAG_ (UINT64_C(1)<<61)
 #ifdef TOR_UNIT_TESTS
 /** This log message should not be intercepted by mock_saving_logv */
 #define LD_NO_MOCK (UINT64_C(1)<<61)