log: prohibit negative values for debug_* configurables.

Signed-off-by: Radoslaw Zarzynski <rzarzyns@redhat.com>

src/common/config.cc

@@ -325,8 +325,13 @@ int md_config_t::parse_config_files_impl(const std::list<std::string> &conf_file
       int log, gather;
       int r = sscanf(val.c_str(), "%d/%d", &log, &gather);
       if (r >= 1) {
-	if (r < 2)
+	if (r < 2) {
 	  gather = log;
+	}
+        if (log < 0 || gather < 0) {
+          cerr << "ERROR for " << as_option << "."
+	       << "log nor gather levels cannot be negative!";
+        }
 	//	cout << "config subsys " << subsys.get_name(o) << " log " << log << " gather " << gather << std::endl;
 	subsys.set_log_level(o, log);
 	subsys.set_gather_level(o, gather);

src/log/SubsystemMap.h

@@ -71,14 +71,21 @@ class SubsystemMap {
   bool should_gather() {
     static_assert(SubV < get_num(), "wrong subsystem ID");
     static_assert(LvlV >= -1 && LvlV <= 200);
-    return LvlV <= m_gather_levels[SubV];
+
+    if constexpr (LvlV <= 0) {
+      // handle the -1 and 0 levels entirely at compile-time.
+      // Such debugs are intended be gathered regardless even
+      // of the user configuration.
+      return true;
+    } else {
+      return LvlV <= static_cast<int>(m_gather_levels[SubV]);
+    }
   }
   bool should_gather(const unsigned sub, int level) {
     assert(sub < m_subsys.size());
-    return level <= m_gather_levels[sub];
+    return level <= static_cast<int>(m_gather_levels[sub]);
   }
 
-  // TODO(rzarzynski): verify the -1 case
   void set_log_level(unsigned subsys, uint8_t log)
   {
     assert(subsys < m_subsys.size());