Add flags for SDL-3 compliance (#663)

* Add flags for SDL-3 compliance

* change check to support older versions of CMake

CMakeLists.txt

@@ -101,17 +101,30 @@ if ("${CMAKE_CXX_COMPILER_ID}" MATCHES "^(Apple)?Clang$")
 endif()
 
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
-set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -O3")
 
 ngraph_var(NGRAPH_WARNINGS_AS_ERRORS DEFAULT "OFF")
 if ("${NGRAPH_WARNINGS_AS_ERRORS}" MATCHES "^(ON|TRUE)$")
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Werror")
     message(STATUS "Warnings as errors")
 endif()
-SET(CMAKE_CXX_FLAGS_RELWITHDEBINFO "-O3 -g")
-SET(CMAKE_CXX_FLAGS_RELEASE "-O3")
+
+SET(CMAKE_CXX_FLAGS_RELWITHDEBINFO "-g")
 SET(CMAKE_CXX_FLAGS_DEBUG  "-O0 -g")
 
+# flags required for SDL-3
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -O2 -fPIE -D_FORTIFY_SOURCE=2")
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wformat -Wformat-security")
+set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -z noexecstack")
+set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -z relro -z now")
+set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -pie")
+if("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
+    if (CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.9)
+        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fstack-protector")
+    else()
+        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fstack-protector-strong")
+    endif()
+endif()
+
 # Set true if CPU backend is built by default
 if (NOT DEFINED NGRAPH_CPU_ENABLE)
     set(NGRAPH_CPU_ENABLE TRUE)

cmake/external_gtest.cmake

@@ -33,7 +33,7 @@ if (${CMAKE_VERSION} VERSION_LESS 3.2)
         # Disable install step
         INSTALL_COMMAND ""
         UPDATE_COMMAND ""
-        CMAKE_ARGS -DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER} -DCMAKE_C_COMPILER=${CMAKE_C_COMPILER}
+        CMAKE_ARGS -DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER} -DCMAKE_C_COMPILER=${CMAKE_C_COMPILER} -DCMAKE_CXX_FLAGS="-fPIC"
         TMP_DIR "${EXTERNAL_PROJECTS_ROOT}/gtest/tmp"
         STAMP_DIR "${EXTERNAL_PROJECTS_ROOT}/gtest/stamp"
         DOWNLOAD_DIR "${EXTERNAL_PROJECTS_ROOT}/gtest/download"
@@ -49,7 +49,7 @@ else()
         # Disable install step
         INSTALL_COMMAND ""
         UPDATE_COMMAND ""
-        CMAKE_ARGS -DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER} -DCMAKE_C_COMPILER=${CMAKE_C_COMPILER}
+        CMAKE_ARGS -DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER} -DCMAKE_C_COMPILER=${CMAKE_C_COMPILER} -DCMAKE_CXX_FLAGS="-fPIC"
         TMP_DIR "${EXTERNAL_PROJECTS_ROOT}/gtest/tmp"
         STAMP_DIR "${EXTERNAL_PROJECTS_ROOT}/gtest/stamp"
         DOWNLOAD_DIR "${EXTERNAL_PROJECTS_ROOT}/gtest/download"