Add spdlog demo app example

Author: ramsafin

app/CMakeLists.txt

@@ -1,5 +1,6 @@
 include(FetchContent)
 
+
 FetchContent_Declare(
   spdlog
   URL https://github.com/gabime/spdlog/archive/refs/tags/v1.15.3.zip
@@ -8,9 +9,17 @@ FetchContent_Declare(
 
 FetchContent_MakeAvailable(spdlog)
 
-
 add_executable(${PROJECT_NAME}_app main.cpp)
-target_link_libraries(${PROJECT_NAME}_app PRIVATE ${PROJECT_NAME}::library)
+
+target_link_libraries(${PROJECT_NAME}_app
+  PRIVATE ${PROJECT_NAME}::library spdlog::spdlog
+)
+
+# mark spdlog headers as system includes to avoid warnings (-Werror)
+get_target_property(_spdlog_includes spdlog::spdlog INTERFACE_INCLUDE_DIRECTORIES)
+target_include_directories(${PROJECT_NAME}_app
+  SYSTEM PRIVATE ${_spdlog_includes}
+)
 
 enable_strict_warnings(${PROJECT_NAME}_app)
 enable_sanitizers(${PROJECT_NAME}_app)

app/main.cpp

@@ -1,13 +1,25 @@
+#include <spdlog/sinks/basic_file_sink.h>
+#include <spdlog/sinks/stdout_color_sinks.h>
+#include <spdlog/spdlog.h>
+
 #include <iostream>
 
 #include "modern_cpp/library.hpp"
 
 int main() {
+  auto console = spdlog::stdout_color_mt("console");
+  spdlog::set_level(spdlog::level::debug);
+
   const int left = 10;
   const int right = 4;
 
-  std::cout << "Add: " << modern_cpp::add(left, right) << '\n';
-  std::cout << "Subtract: " << modern_cpp::subtract(left, right) << '\n';
+  console->info("Calling add({}, {})", left, right);
+  const int sum = modern_cpp::add(left, right);
+  console->info("Result of add: {}", sum);
+
+  console->info("Calling subtract({}, {})", left, right);
+  const int diff = modern_cpp::subtract(left, right);
+  console->info("Result of subtract: {}", diff);
 
   return 0;
 }