logging: Unconditionally log levels >= WARN

Messages with level `WARN` or higher should be logged even when
the category is not provided with `-debug=`, to make sure important
warnings are not lost.

Author: laanwj

src/dbwrapper.cpp

@@ -19,7 +19,7 @@ class CBitcoinLevelDBLogger : public leveldb::Logger {
     // This code is adapted from posix_logger.h, which is why it is using vsprintf.
     // Please do not do this in normal code
     void Logv(const char * format, va_list ap) override {
-            if (!LogAcceptCategory(BCLog::LEVELDB)) {
+            if (!LogAcceptCategory(BCLog::LEVELDB, BCLog::Level::Debug)) {
                 return;
             }
             char buffer[500];
@@ -186,7 +186,7 @@ CDBWrapper::~CDBWrapper()
 
 bool CDBWrapper::WriteBatch(CDBBatch& batch, bool fSync)
 {
-    const bool log_memory = LogAcceptCategory(BCLog::LEVELDB);
+    const bool log_memory = LogAcceptCategory(BCLog::LEVELDB, BCLog::Level::Debug);
     double mem_before = 0;
     if (log_memory) {
         mem_before = DynamicMemoryUsage() / 1024.0 / 1024;

src/logging.h

@@ -166,9 +166,14 @@ namespace BCLog {
 
 BCLog::Logger& LogInstance();
 
-/** Return true if log accepts specified category */
-static inline bool LogAcceptCategory(BCLog::LogFlags category)
+/** Return true if log accepts specified category, at the specified level. */
+static inline bool LogAcceptCategory(BCLog::LogFlags category, BCLog::Level level)
 {
+    // Log messages at Warning and Error level unconditionally, so that
+    // important troubleshooting information doesn't get lost.
+    if (level >= BCLog::Level::Warning) {
+        return true;
+    }
     return LogInstance().WillLogCategory(category);
 }
 
@@ -203,14 +208,14 @@ static inline void LogPrintf_(const std::string& logging_function, const std::st
 // evaluating arguments when logging for the category is not enabled.
 #define LogPrint(category, ...)                                        \
     do {                                                               \
-        if (LogAcceptCategory((category))) {                           \
+        if (LogAcceptCategory((category), BCLog::Level::Debug)) {      \
             LogPrintLevel_(category, BCLog::Level::None, __VA_ARGS__); \
         }                                                              \
     } while (0)
 
 #define LogPrintLevel(level, category, ...)               \
     do {                                                  \
-        if (LogAcceptCategory((category))) {              \
+        if (LogAcceptCategory((category), (level))) {     \
             LogPrintLevel_(category, level, __VA_ARGS__); \
         }                                                 \
     } while (0)

src/timedata.cpp

@@ -99,7 +99,7 @@ void AddTimeData(const CNetAddr& ip, int64_t nOffsetSample)
             }
         }
 
-        if (LogAcceptCategory(BCLog::NET)) {
+        if (LogAcceptCategory(BCLog::NET, BCLog::Level::Debug)) {
             std::string log_message{"time data samples: "};
             for (const int64_t n : vSorted) {
                 log_message += strprintf("%+d  ", n);

src/wallet/coinselection.cpp

@@ -307,7 +307,7 @@ std::optional<SelectionResult> KnapsackSolver(std::vector<OutputGroup>& groups,
             }
         }
 
-        if (LogAcceptCategory(BCLog::SELECTCOINS)) {
+        if (LogAcceptCategory(BCLog::SELECTCOINS, BCLog::Level::Debug)) {
             std::string log_message{"Coin selection best subset: "};
             for (unsigned int i = 0; i < applicable_groups.size(); i++) {
                 if (vfBest[i]) {