Improve CMake correctness and handling

CMakeLists.txt

@@ -37,27 +37,14 @@ foreach(pold "") # Currently Empty
     endif()
 endforeach()
 
-# ==== Define language standard configurations requiring at least c++11 standard
-if(CMAKE_CXX_STANDARD EQUAL "98")
-    message(FATAL_ERROR "CMAKE_CXX_STANDARD:STRING=98 is not supported.")
-endif()
-
-#####
-##  Set the default target properties
-if(NOT CMAKE_CXX_STANDARD)
-    set(CMAKE_CXX_STANDARD 11) # Supported values are ``11``, ``14``, and ``17``.
-endif()
-if(NOT CMAKE_CXX_STANDARD_REQUIRED)
-    set(CMAKE_CXX_STANDARD_REQUIRED ON)
-endif()
-if(NOT CMAKE_CXX_EXTENSIONS)
-    set(CMAKE_CXX_EXTENSIONS OFF)
-endif()
-
-# ====
-
-# Ensures that CMAKE_BUILD_TYPE has a default value
-if(NOT DEFINED CMAKE_BUILD_TYPE)
+# Build the library with C++11 standard support, independent from other including
+# software which may use a different CXX_STANDARD or CMAKE_CXX_STANDARD.
+set(CMAKE_CXX_STANDARD 11)
+set(CMAKE_CXX_EXTENSIONS OFF)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+
+# Ensure that CMAKE_BUILD_TYPE has a value specified for single configuration generators.
+if(NOT DEFINED CMAKE_BUILD_TYPE AND NOT DEFINED CMAKE_CONFIGURATION_TYPES)
     set(CMAKE_BUILD_TYPE Release CACHE STRING
         "Choose the type of build, options are: None Debug Release RelWithDebInfo MinSizeRel Coverage.")
 endif()
@@ -95,16 +82,9 @@ option(JSONCPP_WITH_CMAKE_PACKAGE "Generate and install cmake package files" ON)
 option(JSONCPP_WITH_EXAMPLE "Compile JsonCpp example" OFF)
 option(BUILD_SHARED_LIBS "Build jsoncpp_lib as a shared library." OFF)
 
-# Enable runtime search path support for dynamic libraries on OSX
-if(APPLE)
-    set(CMAKE_MACOSX_RPATH 1)
-endif()
-
 # Adhere to GNU filesystem layout conventions
 include(GNUInstallDirs)
 
-set(DEBUG_LIBNAME_SUFFIX "" CACHE STRING "Optional suffix to append to the library name for a debug build")
-
 set(JSONCPP_USE_SECURE_MEMORY "0" CACHE STRING "-D...=1 to use memory-wiping allocator for STL")
 
 configure_file("${PROJECT_SOURCE_DIR}/version.in"
@@ -115,23 +95,11 @@ macro(use_compilation_warning_as_error)
     if(MSVC)
         # Only enabled in debug because some old versions of VS STL generate
         # warnings when compiled in release configuration.
-        if(CMAKE_VERSION VERSION_GREATER_EQUAL 3.12.0)
-            add_compile_options($<$<CONFIG:Debug>:/WX>)
-        else()
-            set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} /WX ")
-        endif()
+        add_compile_options($<$<CONFIG:Debug>:/WX>)
     elseif(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
-        if(CMAKE_VERSION VERSION_GREATER_EQUAL 3.12.0)
-            add_compile_options(-Werror)
-        else()
-            set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Werror")
-        endif()
+        add_compile_options(-Werror)
         if(JSONCPP_WITH_STRICT_ISO)
-            if(CMAKE_VERSION VERSION_GREATER_EQUAL 3.12.0)
-                add_compile_options(-pedantic-errors)
-            else()
-                set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -pedantic-errors")
-            endif()
+            add_compile_options(-pedantic-errors)
         endif()
     endif()
 endmacro()
@@ -142,57 +110,29 @@ include_directories(${jsoncpp_SOURCE_DIR}/include)
 if(MSVC)
     # Only enabled in debug because some old versions of VS STL generate
     # unreachable code warning when compiled in release configuration.
-    if(CMAKE_VERSION VERSION_GREATER_EQUAL 3.12.0)
-        add_compile_options($<$<CONFIG:Debug>:/W4>)
-    else()
-        set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} /W4 ")
-    endif()
+    add_compile_options($<$<CONFIG:Debug>:/W4>)
 endif()
 
 if(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
     # using regular Clang or AppleClang
-    if(CMAKE_VERSION VERSION_GREATER_EQUAL 3.12.0)
-        add_compile_options(-Wall -Wconversion -Wshadow -Werror=conversion -Werror=sign-compare)
-    else()
-        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wconversion -Wshadow -Werror=conversion -Werror=sign-compare")
-    endif()
+    add_compile_options(-Wall -Wconversion -Wshadow -Werror=conversion -Werror=sign-compare)
 elseif(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
     # using GCC
-    if(CMAKE_VERSION VERSION_GREATER_EQUAL 3.12.0)
-        add_compile_options(-Wall -Wconversion -Wshadow -Wextra)
-    else()
-        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wconversion -Wshadow -Wextra")
-    endif()
+    add_compile_options(-Wall -Wconversion -Wshadow -Wextra)
     # not yet ready for -Wsign-conversion
 
     if(JSONCPP_WITH_STRICT_ISO)
-        if(CMAKE_VERSION VERSION_GREATER_EQUAL 3.12.0)
-            add_compile_options(-Wpedantic)
-        else()
-            set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wpedantic")
-        endif()
+        add_compile_options(-Wpedantic)
     endif()
     if(JSONCPP_WITH_WARNING_AS_ERROR)
-        if(CMAKE_VERSION VERSION_GREATER_EQUAL 3.12.0)
-            add_compile_options(-Werror=conversion)
-        else()
-            set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Werror=conversion")
-        endif()
+        add_compile_options(-Werror=conversion)
     endif()
 elseif(CMAKE_CXX_COMPILER_ID STREQUAL "Intel")
     # using Intel compiler
-    if(CMAKE_VERSION VERSION_GREATER_EQUAL 3.12.0)
-        add_compile_options(-Wall -Wconversion -Wshadow -Wextra -Werror=conversion)
-    else()
-        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wconversion -Wshadow -Wextra -Werror=conversion")
-    endif()
+    add_compile_options(-Wall -Wconversion -Wshadow -Wextra -Werror=conversion)
 
     if(JSONCPP_WITH_STRICT_ISO AND NOT JSONCPP_WITH_WARNING_AS_ERROR)
-        if(CMAKE_VERSION VERSION_GREATER_EQUAL 3.12.0)
-            add_compile_options(-Wpedantic)
-        else()
-            set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wpedantic")
-        endif()
+        add_compile_options(-Wpedantic)
     endif()
 endif()
 

example/CMakeLists.txt

@@ -1,18 +1,15 @@
 #vim: et ts =4 sts = 4 sw = 4 tw = 0
-cmake_minimum_required(VERSION 3.1)
-
 set(EXAMPLES
     readFromString
     readFromStream
     stringWrite
     streamWrite
 )
 add_definitions(-D_GLIBCXX_USE_CXX11_ABI)
-set_property(DIRECTORY PROPERTY COMPILE_OPTIONS ${EXTRA_CXX_FLAGS})
 
-if("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wextra ")
-else()
+if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU" OR CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+    add_compile_options(-Wall -Wextra)
+elseif(CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
     add_definitions(
         -D_SCL_SECURE_NO_WARNINGS
         -D_CRT_SECURE_NO_WARNINGS

src/lib_json/CMakeLists.txt

@@ -1,13 +1,6 @@
-if(CMAKE_COMPILER_IS_GNUCXX)
-    #Get compiler version.
-    execute_process(COMMAND ${CMAKE_CXX_COMPILER} -dumpversion
-        OUTPUT_VARIABLE GNUCXX_VERSION
-    )
-
+if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU" AND CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 4.1.2)
     #-Werror=* was introduced -after- GCC 4.1.2
-    if(GNUCXX_VERSION VERSION_GREATER 4.1.2)
-        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Werror=strict-aliasing")
-    endif()
+    add_compile_options("-Werror=strict-aliasing")
 endif()
 
 include(CheckIncludeFileCXX)
@@ -81,12 +74,13 @@ if(BUILD_SHARED_LIBS)
     endif()
 endif()
 
-
 add_library(jsoncpp_lib ${PUBLIC_HEADERS} ${jsoncpp_sources})
-set_target_properties(jsoncpp_lib PROPERTIES VERSION ${JSONCPP_VERSION} SOVERSION ${JSONCPP_SOVERSION})
-set_target_properties(jsoncpp_lib PROPERTIES OUTPUT_NAME jsoncpp
-                        DEBUG_OUTPUT_NAME jsoncpp${DEBUG_LIBNAME_SUFFIX})
-set_target_properties(jsoncpp_lib PROPERTIES POSITION_INDEPENDENT_CODE ON)
+set_target_properties( jsoncpp_lib PROPERTIES
+    OUTPUT_NAME jsoncpp
+    VERSION ${JSONCPP_VERSION}
+    SOVERSION ${JSONCPP_SOVERSION}
+    POSITION_INDEPENDENT_CODE ON
+)
 
 # Set library's runtime search path on OSX
 if(APPLE)