fix: unable to properly set USE_FMT

Author: Yimura

CMakeLists.txt

@@ -1,18 +1,12 @@
 cmake_minimum_required(VERSION 3.20)
 
+option(USE_FMT "Use fmt::format instead of std::format" 0)
+
 project(AsyncLogger LANGUAGES CXX VERSION 0.0.1 DESCRIPTION "A lightweight C++20 asyncronous logger.")
 
 set(SRC_DIR "${PROJECT_SOURCE_DIR}/src")
 set(PUBLIC_HEADER_DIR "${PROJECT_SOURCE_DIR}/include")
 
-# check std::format support
-if(NOT USE_FMT)
-    include(CheckIncludeFileCXX)
-    check_include_file_cxx("format" CXX_FORMAT_SUPPORT)
-else()
-    set(CXX_FORMAT_SUPPORT 0)
-endif()
-
 file(GLOB_RECURSE SRC_FILES
     "${SRC_DIR}/**.cpp"
     "${SRC_DIR}/**.hpp"
@@ -23,7 +17,11 @@ file(GLOB_RECURSE PUBLIC_HEADER_FILES
 
 add_library(${PROJECT_NAME} STATIC ${SRC_FILES} ${PUBLIC_HEADER_FILES})
 
-if(CXX_FORMAT_SUPPORT)
+# check std::format support
+include(CheckIncludeFileCXX)
+check_include_file_cxx("format" CXX_FORMAT_SUPPORT)
+
+if(CXX_FORMAT_SUPPORT AND NOT USE_FMT)
     message(STATUS "Using std::format for formatting, you can set USE_FMT to force fmt::format instead.")
 else()
     message(STATUS "Using fmt::format for formatting.")
@@ -37,12 +35,16 @@ else()
     )
     FetchContent_MakeAvailable(fmt)
 
+    target_compile_definitions(${PROJECT_NAME} PRIVATE USE_FMT=1)
     target_link_libraries(${PROJECT_NAME} fmt)
 endif()
 
+unset(USE_FMT CACHE)
+unset(CXX_FORMAT_SUPPORT CACHE)
+
 # does the -lpthread linking for us on Linux
 find_package(Threads REQUIRED)
-target_link_libraries(${PROJECT_NAME} Threads::Threads )
+target_link_libraries(${PROJECT_NAME} Threads::Threads)
 
 set_property(TARGET ${PROJECT_NAME} PROPERTY CXX_STANDARD 20)
 
@@ -52,4 +54,4 @@ target_precompile_headers(${PROJECT_NAME} PRIVATE "${SRC_DIR}/common.hpp")
 
 # public stuff
 set_target_properties(${PROJECT_NAME} PROPERTIES PUBLIC_HEADER "${PUBLIC_HEADER_FILES}")
-target_include_directories(${PROJECT_NAME} PUBLIC "${PUBLIC_HEADER_DIR}")
+target_include_directories(${PROJECT_NAME} PUBLIC "${PUBLIC_HEADER_DIR}")

include/AsyncLogger/Logger.hpp

@@ -1,5 +1,5 @@
 #pragma once
-#if !defined(USE_FMT) && CXX_FORMAT_SUPPORT
+#if !defined(USE_FMT)
     #include <format>
     #define FORMAT std::format
     #define VFORMAT std::vformat