Implements shared library compatible global set_default_logger.

The key difference is that registry::instance is moved to a cpp when
compiling the library.

CMakeLists.txt

@@ -137,7 +137,7 @@ message(STATUS "Build type: " ${CMAKE_BUILD_TYPE})
 # ---------------------------------------------------------------------------------------
 # Static/Shared library (shared not supported in windows yet)
 # ---------------------------------------------------------------------------------------
-set(SPDLOG_SRCS src/spdlog.cpp src/stdout_sinks.cpp src/color_sinks.cpp src/file_sinks.cpp src/async.cpp src/cfg.cpp)
+set(SPDLOG_SRCS src/spdlog.cpp src/stdout_sinks.cpp src/color_sinks.cpp src/file_sinks.cpp src/registry.cpp src/async.cpp src/cfg.cpp)
 
 if(NOT SPDLOG_USE_STD_FORMAT AND NOT SPDLOG_FMT_EXTERNAL AND NOT SPDLOG_FMT_EXTERNAL_HO)
     list(APPEND SPDLOG_SRCS src/fmt.cpp)

example/CMakeLists.txt

@@ -8,6 +8,22 @@ if(NOT TARGET spdlog)
     find_package(spdlog REQUIRED)
 endif()
 
+# ---------------------------------------------------------------------------------------
+# Example of using shared libraries
+# ---------------------------------------------------------------------------------------
+add_library(mylibrary SHARED mylibrary.cpp mylibrary.h)
+target_link_libraries(mylibrary PRIVATE spdlog::spdlog)
+target_compile_definitions(mylibrary PUBLIC SPDLOG_COMPILED_LIB)
+
+add_executable(library_example library_example.cpp)
+target_link_libraries(library_example PRIVATE spdlog::spdlog mylibrary)
+target_compile_definitions(library_example PUBLIC SPDLOG_COMPILED_LIB)
+
+if(SPDLOG_BUILD_SHARED OR BUILD_SHARED_LIBS)
+    target_compile_definitions(mylibrary PUBLIC SPDLOG_SHARED_LIB)
+    target_compile_definitions(library_example PUBLIC SPDLOG_SHARED_LIB)
+endif()
+
 # ---------------------------------------------------------------------------------------
 # Example of using pre-compiled library
 # ---------------------------------------------------------------------------------------

example/library_example.cpp

@@ -0,0 +1,21 @@
+//
+// Copyright(c) 2021
+// Distributed under the MIT License (http://opensource.org/licenses/MIT)
+
+#include "spdlog/spdlog.h"
+#include "spdlog/sinks/basic_file_sink.h"
+#include "mylibrary.h"
+
+int main(int, char *[])
+{
+    auto new_logger = spdlog::basic_logger_mt("library_example", "logs/library_example.txt", true);
+    spdlog::set_level(spdlog::level::info);
+
+    spdlog::set_default_logger(new_logger);
+    #ifndef SPDLOG_SHARED_LIB
+    lib::set_logger(new_logger);
+    #endif
+
+    spdlog::info("This message is from the base application");
+    lib::test();
+}

example/mylibrary.cpp

@@ -0,0 +1,22 @@
+//
+// Copyright(c) 2021
+// Distributed under the MIT License (http://opensource.org/licenses/MIT)
+
+#include "mylibrary.h"
+
+#include <spdlog/spdlog.h>
+
+namespace lib
+{
+    const std::string logger_name = "example";
+
+    void set_logger(const std::shared_ptr<spdlog::logger>& logger)
+    {
+        spdlog::set_default_logger(logger);
+    }
+
+    void test()
+    {
+        spdlog::info("This message is from the shared library.");
+    }
+}

example/mylibrary.h

@@ -0,0 +1,19 @@
+//
+// Copyright(c) 2021
+// Distributed under the MIT License (http://opensource.org/licenses/MIT)
+
+#ifdef _WIN32
+#define LIB_EXPORT __declspec(dllexport)
+#else // !defined(_WIN32)
+#define LIB_EXPORT
+#endif
+
+#include <memory>
+#include <spdlog/logger.h>
+
+namespace lib
+{
+    LIB_EXPORT void set_logger(const std::shared_ptr<spdlog::logger>& logger);
+
+    LIB_EXPORT void test();
+}

include/spdlog/details/registry-inl.h

@@ -288,11 +288,13 @@ SPDLOG_INLINE void registry::set_levels(log_levels levels, level::level_enum *gl
     }
 }
 
+#ifndef SPDLOG_COMPILED_LIB
 SPDLOG_INLINE registry &registry::instance()
 {
     static registry s_instance;
     return s_instance;
 }
+#endif
 
 SPDLOG_INLINE void registry::throw_if_exists_(const std::string &logger_name)
 {

src/registry.cpp

@@ -0,0 +1,20 @@
+// Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
+// Distributed under the MIT License (http://opensource.org/licenses/MIT)
+
+#ifndef SPDLOG_COMPILED_LIB
+#    error Please define SPDLOG_COMPILED_LIB to compile this file.
+#endif
+
+#include <spdlog/details/registry.h>
+
+namespace spdlog {
+namespace details {
+
+registry &registry::instance()
+{
+    static registry s_instance;
+    return s_instance;
+}
+
+}
+}