Revert changes to null_mutex

CMakeLists.txt

@@ -242,6 +242,10 @@ if (BUILD_SHARED_LIBS)
     endif ()
     add_library(spdlog SHARED ${VERSION_RC})
     target_compile_definitions(spdlog PUBLIC SPDLOG_SHARED_LIB)
+    set_target_properties(spdlog PROPERTIES
+            CXX_VISIBILITY_PRESET hidden
+            VISIBILITY_INLINES_HIDDEN ON)
+
     if (MSVC)
         # disable dlls related warnings on msvc
         target_compile_options(spdlog PUBLIC $<$<AND:$<CXX_COMPILER_ID:MSVC>,$<NOT:$<COMPILE_LANGUAGE:CUDA>>>:/wd4251

include/spdlog/details/null_mutex.h

@@ -7,7 +7,6 @@
 #include <utility>
 
 // null, no cost dummy "mutex" and dummy "atomic" log level
-
 namespace spdlog {
 namespace details {
 struct null_mutex {

include/spdlog/sinks/base_sink.h

@@ -36,7 +36,7 @@ public:
 protected:
     // sink formatter
     std::unique_ptr<spdlog::formatter> formatter_;
-    Mutex mutex_;
+    mutable Mutex mutex_;
 
     virtual void sink_it_(const details::log_msg &msg) = 0;
     virtual void flush_() = 0;

src/sinks/ansicolor_sink.cpp

@@ -117,6 +117,8 @@ ansicolor_stderr_sink<Mutex>::ansicolor_stderr_sink(color_mode mode)
 
 // template instantiations
 #include "spdlog/details/null_mutex.h"
+template class SPDLOG_API spdlog::sinks::ansicolor_sink<std::mutex>;
+template class SPDLOG_API spdlog::sinks::ansicolor_sink<spdlog::details::null_mutex>;
 template class SPDLOG_API spdlog::sinks::ansicolor_stdout_sink<std::mutex>;
 template class SPDLOG_API spdlog::sinks::ansicolor_stdout_sink<spdlog::details::null_mutex>;
 template class SPDLOG_API spdlog::sinks::ansicolor_stderr_sink<std::mutex>;

src/sinks/rotating_file_sink.cpp

@@ -142,4 +142,4 @@ bool rotating_file_sink<Mutex>::rename_file_(const filename_t &src_filename, con
 // template instantiations
 #include "spdlog/details/null_mutex.h"
 template class SPDLOG_API spdlog::sinks::rotating_file_sink<std::mutex>;
-template class SPDLOG_API spdlog::sinks::rotating_file_sink<spdlog::details::null_mutex>;
+template class SPDLOG_API spdlog::sinks::rotating_file_sink<spdlog::details::null_mutex>;