ensure log usable in static initialize stage

src/babylon/logging/log_stream.cpp

@@ -25,12 +25,15 @@ void LogStream::do_end() noexcept {}
 DefaultLogStream::DefaultLogStream() noexcept
     :
 #if __clang__ || BABYLON_GCC_VERSION >= 50000
-      LogStream {*::std::cerr.rdbuf()} {
-}
+      LogStream {*::std::cerr.rdbuf()}
 #else  // !__clang__ && BABYLON_GCC_VERSION < 50000
-      LogStream(*::std::cerr.rdbuf()) {
-}
+      LogStream(*::std::cerr.rdbuf())
 #endif // !__clang__ && BABYLON_GCC_VERSION < 50000
+{
+  // Ensure std::cerr is initialized
+  ::std::ios_base::Init();
+  rdbuf(::std::cerr.rdbuf());
+}
 
 ::std::mutex& DefaultLogStream::mutex() noexcept {
   static ::std::mutex mutex;
@@ -61,14 +64,17 @@ void DefaultLogStream::do_end() noexcept {
 NullLogStream::NullLogStream() noexcept
     :
 #if __clang__ || BABYLON_GCC_VERSION >= 50000
-      LogStream {s_buffer} {
+      LogStream {buffer()} {
 }
 #else  // !__clang__ && BABYLON_GCC_VERSION < 50000
-      LogStream(s_buffer) {
+      LogStream(buffer()) {
 }
 #endif // !__clang__ && BABYLON_GCC_VERSION < 50000
 
-NullLogStream::Buffer NullLogStream::s_buffer;
+NullLogStream::Buffer& NullLogStream::buffer() noexcept {
+  static Buffer static_buffer;
+  return static_buffer;
+}
 // NullLogStream end
 ////////////////////////////////////////////////////////////////////////////////
 

src/babylon/logging/log_stream.h

@@ -175,7 +175,8 @@ class NullLogStream : public LogStream {
 
  private:
   class Buffer;
-  static Buffer s_buffer;
+
+  static Buffer& buffer() noexcept;
 };
 
 ////////////////////////////////////////////////////////////////////////////////

test/logging/BUILD

@@ -74,6 +74,17 @@ cc_test(
   ]
 )
 
+cc_test(
+  name = 'test_log_statically',
+  srcs = ['test_log_statically.cpp'],
+  copts = BABYLON_COPTS,
+  linkstatic = True,
+  deps = [
+    '//:logging_logger',
+    '@com_google_googletest//:gtest_main',
+  ]
+)
+
 cc_test(
   name = 'test_rolling_file_object',
   srcs = ['test_rolling_file_object.cpp'],

test/logging/test_log_statically.cpp

@@ -0,0 +1,9 @@
+#include "babylon/logging/logger.h"
+
+// Do BABYLON_LOG at very begining of the program.
+// Check whether log system is ensured to be ready in default state
+__attribute__((init_priority(101))) static struct StaticallyInitialized {
+  StaticallyInitialized() {
+    BABYLON_LOG(INFO) << "log in static initialize stage is fine";
+  }
+} statically_initialized_instance;