Added a nullptr check in macro-free log functions (#895)

Author: NanKendrik

CHANGELOG.md

@@ -99,6 +99,8 @@
 ## v11.1.0
 
 - Fixed thread-local context duplication across shared libraries ([#890](https://github.com/odygrd/quill/issues/890))
+- Added a `nullptr` check in macro-free log functions (`LogFunctions.h`) to allow calls with an uninitialized logger.
+  Macro-based logging remains deliberately unchanged ([#894](https://github.com/odygrd/quill/issues/894))
 
 ## v11.0.2
 

docs/macro_free_mode.rst

@@ -20,6 +20,8 @@ The macro-free approach comes with performance implications:
 
 4. **Backend Thread Impact**: Reduced throughput in the backend due to runtime metadata storage and processing
 
+5. **Additional Safety Checks**: The macro-free functions perform a runtime check for `nullptr` logger. This can be useful in cases where a user might forget to initialize a logger or intentionally wants logging calls to become no-ops when the logger is null. (Note that there are also multiple ways to achieve no-op logging with macros, e.g., by setting the log level to `None`)
+
 For performance-critical logging paths, the macro-based logging interface is recommended.
 
 Available Functions

include/quill/LogFunctions.h

@@ -325,6 +325,11 @@ template <typename TLogger, typename... Args>
 QUILL_ATTRIBUTE_HOT void log(TLogger* logger, char const* tags, LogLevel log_level, char const* fmt,
                              SourceLocation const& location, Args&&... args)
 {
+  if (QUILL_UNLIKELY(!logger))
+  {
+    return;
+  }
+
   static constexpr MacroMetadata macro_metadata{
     "[placeholder]", "[placeholder]", "[placeholder]",
     nullptr,         LogLevel::None,  MacroMetadata::Event::LogWithRuntimeMetadataHybridCopy};

test/integration_tests/MacroFreeMultiFrontendThreadsTest.cpp

@@ -60,11 +60,33 @@ TEST_CASE("macro_free_multi_frontend_threads")
       });
   }
 
+  // wait all threads to join
   for (auto& elem : threads)
   {
     elem.join();
   }
 
+  // log from main thread - get logger from the first thread
+  Logger* t0_logger = Frontend::get_logger(logger_name_prefix + std::to_string(0));
+  REQUIRE(t0_logger);
+
+  t0_logger->set_log_level(quill::LogLevel::TraceL3);
+
+  tracel3(t0_logger, "a trace_l3 message");
+  tracel2(t0_logger, "a trace_l2 message");
+  tracel1(t0_logger, "a trace_l1 message");
+  debug(t0_logger, "a debug message");
+  info(t0_logger, "an info message");
+  notice(t0_logger, "a notice message");
+  warning(t0_logger, "a warning message");
+  error(t0_logger, "an error message");
+  critical(t0_logger, "a critical message");
+
+  // with nullptr
+  Logger* null_logger = nullptr;
+  info(null_logger, "null");
+  warning(null_logger, "null");
+
   // flush all log and remove all loggers
   for (Logger* logger : Frontend::get_all_loggers())
   {
@@ -77,7 +99,7 @@ TEST_CASE("macro_free_multi_frontend_threads")
 
   // Read file and check
   std::vector<std::string> const file_contents = quill::testing::file_contents(filename);
-  REQUIRE_EQ(file_contents.size(), number_of_messages * number_of_threads);
+  REQUIRE_EQ(file_contents.size(), number_of_messages * number_of_threads + 9);
 
   for (size_t i = 0; i < number_of_threads; ++i)
   {
@@ -91,5 +113,15 @@ TEST_CASE("macro_free_multi_frontend_threads")
     }
   }
 
+  REQUIRE(testing::file_contains(file_contents, "LOG_TRACE_L3  logger_0     a trace_l3 message"));
+  REQUIRE(testing::file_contains(file_contents, "LOG_TRACE_L2  logger_0     a trace_l2 message"));
+  REQUIRE(testing::file_contains(file_contents, "LOG_TRACE_L1  logger_0     a trace_l1 message"));
+  REQUIRE(testing::file_contains(file_contents, "LOG_DEBUG     logger_0     a debug message"));
+  REQUIRE(testing::file_contains(file_contents, "LOG_INFO      logger_0     an info message"));
+  REQUIRE(testing::file_contains(file_contents, "LOG_NOTICE    logger_0     a notice message"));
+  REQUIRE(testing::file_contains(file_contents, "LOG_WARNING   logger_0     a warning message"));
+  REQUIRE(testing::file_contains(file_contents, "LOG_ERROR     logger_0     an error message"));
+  REQUIRE(testing::file_contains(file_contents, "LOG_CRITICAL  logger_0     a critical message"));
+
   testing::remove_file(filename);
 }