Use target_compile_features to target C++11 (#7122)

CMakeLists.txt

@@ -41,8 +41,7 @@ option(FLATBUFFERS_BUILD_FLATC "Enable the build of the flatbuffers compiler"
 option(FLATBUFFERS_STATIC_FLATC "Build flatbuffers compiler with -static flag"
        OFF)
 option(FLATBUFFERS_BUILD_FLATHASH "Enable the build of flathash" ON)
-option(FLATBUFFERS_BUILD_BENCHMARKS "Enable the build of flatbenchmark. \"
-       Requires C++11."
+option(FLATBUFFERS_BUILD_BENCHMARKS "Enable the build of flatbenchmark."
        OFF)
 option(FLATBUFFERS_BUILD_GRPCTEST "Enable the build of grpctest" OFF)
 option(FLATBUFFERS_BUILD_SHAREDLIB
@@ -274,13 +273,6 @@ if(EXISTS "${CMAKE_TOOLCHAIN_FILE}")
   # is being configured externally
   message(STATUS "Using toolchain file: ${CMAKE_TOOLCHAIN_FILE}.")
 elseif(CMAKE_COMPILER_IS_GNUCXX)
-  if(CYGWIN)
-    set(CMAKE_CXX_FLAGS
-      "${CMAKE_CXX_FLAGS} -std=gnu++11")
-  else(CYGWIN)
-    set(CMAKE_CXX_FLAGS
-      "${CMAKE_CXX_FLAGS} -std=c++0x")
-  endif(CYGWIN)
   set(CMAKE_CXX_FLAGS
     "${CMAKE_CXX_FLAGS} -Wall -pedantic -Werror -Wextra -Werror=shadow")
   set(FLATBUFFERS_PRIVATE_CXX_FLAGS "-Wold-style-cast")
@@ -313,13 +305,9 @@ elseif(MSVC)
 
 elseif(${CMAKE_CXX_COMPILER_ID} MATCHES "Clang")
   if(APPLE)
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
-
     if(FLATBUFFERS_OSX_BUILD_UNIVERSAL)
       set(CMAKE_OSX_ARCHITECTURES "arm64;x86_64")
     endif()
-  else()
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++0x")
   endif()
 
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -pedantic -Werror -Wextra -Wno-unused-parameter")
@@ -403,6 +391,7 @@ if(FLATBUFFERS_BUILD_FLATLIB)
   target_include_directories(flatbuffers INTERFACE
     $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>)
   target_compile_options(flatbuffers PRIVATE "${FLATBUFFERS_PRIVATE_CXX_FLAGS}")
+  target_compile_features(flatbuffers PUBLIC cxx_std_11)
   if(FLATBUFFERS_ENABLE_PCH)
     add_pch_to_target(flatbuffers include/flatbuffers/pch/pch.h)
   endif()
@@ -414,6 +403,7 @@ if(FLATBUFFERS_BUILD_FLATC)
     add_pch_to_target(flatc include/flatbuffers/pch/flatc_pch.h)
   endif()
   target_compile_options(flatc PRIVATE "${FLATBUFFERS_PRIVATE_CXX_FLAGS}")
+  target_compile_features(flatc PUBLIC cxx_std_11)
   if(FLATBUFFERS_CODE_SANITIZE AND NOT WIN32)
     add_fsanitize_to_target(flatc ${FLATBUFFERS_CODE_SANITIZE})
   endif()
@@ -431,11 +421,12 @@ endif()
 
 if(FLATBUFFERS_BUILD_FLATHASH)
   add_executable(flathash ${FlatHash_SRCS})
+  target_compile_features(flathash PUBLIC cxx_std_11)
 endif()
 
 if(FLATBUFFERS_BUILD_SHAREDLIB)
   add_library(flatbuffers_shared SHARED ${FlatBuffers_Library_SRCS})
-
+  target_compile_features(flatbuffers_shared PUBLIC cxx_std_11)
   # Shared object version: "major.minor.micro"
   # - micro updated every release when there is no API/ABI changes
   # - minor updated when there are additions in API/ABI
@@ -556,6 +547,7 @@ if(FLATBUFFERS_BUILD_TESTS)
   endif()
   include_directories(${CMAKE_CURRENT_BINARY_DIR}/tests)
   add_executable(flattests ${FlatBuffers_Tests_SRCS})
+  target_compile_features(flattests PUBLIC cxx_std_11)
   add_dependencies(flattests generated_code)
   set_property(TARGET flattests
     PROPERTY COMPILE_DEFINITIONS FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE
@@ -568,10 +560,13 @@ if(FLATBUFFERS_BUILD_TESTS)
   compile_flatbuffers_schema_to_binary(samples/monster.fbs)
   include_directories(${CMAKE_CURRENT_BINARY_DIR}/samples)
   add_executable(flatsamplebinary ${FlatBuffers_Sample_Binary_SRCS})
+  target_compile_features(flatsamplebinary PUBLIC cxx_std_11)
   add_dependencies(flatsamplebinary generated_code)
   add_executable(flatsampletext ${FlatBuffers_Sample_Text_SRCS})
+  target_compile_features(flatsampletext PUBLIC cxx_std_11)
   add_dependencies(flatsampletext generated_code)
   add_executable(flatsamplebfbs ${FlatBuffers_Sample_BFBS_SRCS})
+  target_compile_features(flatsamplebfbs PUBLIC cxx_std_11)
   add_dependencies(flatsamplebfbs generated_code)
 
   if(FLATBUFFERS_BUILD_CPP17)
@@ -610,6 +605,7 @@ if(FLATBUFFERS_BUILD_GRPCTEST)
   find_package(gRPC CONFIG REQUIRED)
   add_executable(grpctest ${FlatBuffers_GRPCTest_SRCS})
   add_dependencies(grpctest generated_code)
+  target_compile_features(grpctest PRIVATE cxx_std_11)
   target_link_libraries(grpctest PRIVATE gRPC::grpc++_unsecure gRPC::grpc_unsecure gRPC::gpr pthread dl)
   if(FLATBUFFERS_CODE_SANITIZE AND NOT WIN32)
     # GRPC test has problems with alignment and will fail under ASAN/UBSAN.