Bug 1417 - Android: OpenAL-Soft toolchain.android.cmake cleanup and NDK r20 adoption llvm: clang libc++

All properties are now aligned with gluegen/make/scripts/setenv-android-tools.sh.
User must set ANDROID_NDK, ANDROID_HOST_TAG, ANDROID_API_LEVEL and one of
NDK_CPU_X86_64, NDK_CPU_X86, NDK_CPU_ARM64, NDK_CPU_ARM_V7A, NDK_CPU_ARM.

2 files changed, 137 insertions, 134 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 7cdd7e18..824659b7 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,6 +1,6 @@
 # CMake build file list for OpenAL
 
-CMAKE_MINIMUM_REQUIRED(VERSION 3.0.2)
+CMAKE_MINIMUM_REQUIRED(VERSION 3.2.0)
 
 PROJECT(OpenAL)
 
diff --git a/cmake/toolchain.android.cmake b/cmake/toolchain.android.cmake
index 37474a7e..5e5a7124 100644
--- a/cmake/toolchain.android.cmake
+++ b/cmake/toolchain.android.cmake
@@ -1,4 +1,25 @@
-# Adapted from http://code.google.com/p/android-cmake/
+#
+# Aligned with NDK r19 using LLVM's clang and C++ STL
+#
+
+#
+# Required variables to be set by user:
+#                               (gluegen/make/scripts/setenv-android-tools.sh env var)
+# - ANDROID_NDK              := ${env.ANDROID_NDK}         [/opt/android-sdk/ndk/20.00]
+# - ANDROID_HOST_TAG         := ${env.ANDROID_HOST_TAG}    [linux-x86_64, ..]
+# - ANDROID_API_LEVEL        := ${env.ANDROID_API_LEVEL}   [24]
+#
+# and one of the following CPU target flags:
+#
+# - NDK_CPU_X86_64
+# - NDK_CPU_X86
+# - NDK_CPU_ARM64
+# - NDK_CPU_ARM_V7A
+# - NDK_CPU_ARM
+#
+# (Will be preserved for try_compile() via CMAKE_TRY_COMPILE_PLATFORM_VARIABLES)
+
+set(CMAKE_CROSSCOMPILING true)
 
 set(CMAKE_SYSTEM_NAME Linux)
 set(CMAKE_SYSTEM_VERSION 1)
@@ -12,166 +33,144 @@ endif()
 set(APPLE false)
 set(UNIX true)
 
-set(ANDROID_NDK_DEFAULT_SEARCH_PATH /opt/android-ndk)
-set(ANDROID_NDK_SUPPORTED_VERSIONS -r8d -r8 -r7 -r6 -r5c -r5b -r5 "")
-set(ANDROID_NDK_TOOLCHAIN_DEFAULT_SEARCH_PATH /opt/android-toolchain)
 set(TOOL_OS_SUFFIX "")
 
-if(NOT DEFINED ANDROID_NDK)
-	set(ANDROID_NDK "$ENV{ANDROID_NDK}")
-endif()
+unset(CMAKE_TRY_COMPILE_PLATFORM_VARIABLES)
 
-if(NOT DEFINED ANDROID_NDK_TOOLCHAIN_ROOT)
-	set(ANDROID_NDK_TOOLCHAIN_ROOT $ENV{ANDROID_NDK_TOOLCHAIN_ROOT})
+if(NOT DEFINED ANDROID_NDK)
+    message(FATAL_ERROR "Undefined ANDROID_NDK")
+	#set(ANDROID_NDK "$ENV{ANDROID_NDK}")
+else()
+    set(CMAKE_TRY_COMPILE_PLATFORM_VARIABLES ${CMAKE_TRY_COMPILE_PLATFORM_VARIABLES} ANDROID_NDK)
 endif()
 
 if(NOT EXISTS "${ANDROID_NDK}")
-	foreach(ndk_version ${ANDROID_NDK_SUPPORTED_VERSIONS})
-		if(EXISTS ${ANDROID_NDK_DEFAULT_SEARCH_PATH}${ndk_version})
-			set(ANDROID_NDK "${ANDROID_NDK_DEFAULT_SEARCH_PATH}${ndk_version}")
-			message(STATUS "Using default path for android NDK ${ANDROID_NDK}")
-			message(STATUS "  If you prefer to use a different location, please define the variable: ANDROID_NDK")
-			break()
-		endif()
-	endforeach()
+    message(FATAL_ERROR "Not existing ANDROID_NDK ${ANDROID_NDK}")
 endif()
 
-if(EXISTS "${ANDROID_NDK}")
-    if(NOT DEFINED ANDROID_TOOLCHAIN_SYSTEM)
-        if(APPLE)
-            set(ANDROID_TOOLCHAIN_SYSTEM "darwin-x86")
-        elseif(WIN32)
-            set(ANDROID_TOOLCHAIN_SYSTEM "windows")
-            set(TOOL_OS_SUFFIX ".exe")
-        elseif(UNIX)
-            set(ANDROID_TOOLCHAIN_SYSTEM "linux-x86")
-        else()
-            message(FATAL_ERROR "Your platform is not supported")
-        endif()
-    endif()
-
-	if(NOT ANDROID_API_LEVEL GREATER 2)
-		if(NDK_CPU_ARM64)
-			set(ANDROID_API_LEVEL 21)
-		elseif(NDK_CPU_X86)
-			set(ANDROID_API_LEVEL 9)
-		else()
-			set(ANDROID_API_LEVEL 5)
-		endif()
-		message(STATUS "Using default android API level android-${ANDROID_API_LEVEL}")
-		message(STATUS "  If you prefer to use a different API level, please define the variable: ANDROID_API_LEVEL")
-	endif()
-
-	if (NDK_CPU_X86)
-		set(ANDROID_TOOLCHAIN_PREFIX "i686-android-linux")
-		set(ANDROID_TOOLCHAIN_NAME "x86")
-		set(ANDROID_TOOLCHAIN_PLATFORM_NAME "x86")
-    elseif(NDK_CPU_ARM64)
-		set(ANDROID_TOOLCHAIN_PREFIX "aarch64-linux-android")
-		set(ANDROID_TOOLCHAIN_NAME "${ANDROID_TOOLCHAIN_PREFIX}")
-		set(ANDROID_TOOLCHAIN_PLATFORM_NAME "arm64")
-	else()
-		set(ANDROID_TOOLCHAIN_PREFIX "arm-linux-androideabi")
-		set(ANDROID_TOOLCHAIN_NAME "${ANDROID_TOOLCHAIN_PREFIX}")
-		set(ANDROID_TOOLCHAIN_PLATFORM_NAME "arm")
-	endif()
-
-	if (NOT DEFINED ANDROID_TOOLCHAIN_VERSION)
-		set(SUPPORTED_TOOLCHAIN_VERSIONS 4.4.0 4.4.3 4.6.0 4.6.1 4.6.2 4.6.3 4.7 4.8 4.9)
-		foreach(gcc_version ${SUPPORTED_TOOLCHAIN_VERSIONS})
-			if (EXISTS "${ANDROID_NDK}/toolchains/${ANDROID_TOOLCHAIN_NAME}-${gcc_version}")
-				set(ANDROID_TOOLCHAIN_VERSION ${gcc_version})
-			endif()
-		endforeach()
-		if(NOT DEFINED ANDROID_TOOLCHAIN_VERSION)
-			message(FATAL_ERROR "Unable to find toolchain")
-		else()
-			message(STATUS "Using auto-detected toolchain ${ANDROID_TOOLCHAIN_NAME}-${ANDROID_TOOLCHAIN_VERSION}")
-		endif()
-	endif()
-	if (EXISTS "${ANDROID_NDK}/toolchains/clang-android-${ANDROID_TOOLCHAIN_VERSION}")
-		set (ANDROID_TOOLCHAIN_NAME "clang-android")
-		message(STATUS "Found clang toolchain ${ANDROID_TOOLCHAIN_NAME}-${ANDROID_TOOLCHAIN_VERSION}")
-	endif()
-
-	set(ANDROID_NDK_SYSROOT "${ANDROID_NDK}/platforms/android-${ANDROID_API_LEVEL}/arch-${ANDROID_TOOLCHAIN_PLATFORM_NAME}")
-	set(ANDROID_NDK_TOOLCHAIN_ROOT "${ANDROID_NDK}/toolchains/${ANDROID_TOOLCHAIN_NAME}-${ANDROID_TOOLCHAIN_VERSION}/prebuilt/${ANDROID_TOOLCHAIN_SYSTEM}")
+if(NOT DEFINED ANDROID_HOST_TAG)
+    message(FATAL_ERROR "Undefined ANDROID_HOST_TAG")
+else()
+    set(CMAKE_TRY_COMPILE_PLATFORM_VARIABLES ${CMAKE_TRY_COMPILE_PLATFORM_VARIABLES} ANDROID_HOST_TAG)
+endif()
 
+if(NOT ANDROID_API_LEVEL GREATER 2)
+    set(ANDROID_API_LEVEL 24)
+    message(STATUS "Using default android API level android-${ANDROID_API_LEVEL}")
+else()
+    set(CMAKE_TRY_COMPILE_PLATFORM_VARIABLES ${CMAKE_TRY_COMPILE_PLATFORM_VARIABLES} ANDROID_API_LEVEL)
 endif()
 
-set(CMAKE_C_COMPILER   "${ANDROID_NDK_TOOLCHAIN_ROOT}/bin/${ANDROID_TOOLCHAIN_PREFIX}-gcc${TOOL_OS_SUFFIX}"     CACHE PATH "gcc" FORCE)
-set(CMAKE_CXX_COMPILER "${ANDROID_NDK_TOOLCHAIN_ROOT}/bin/${ANDROID_TOOLCHAIN_PREFIX}-g++${TOOL_OS_SUFFIX}"     CACHE PATH "g++" FORCE)
-set(CMAKE_AR           "${ANDROID_NDK_TOOLCHAIN_ROOT}/bin/${ANDROID_TOOLCHAIN_PREFIX}-ar${TOOL_OS_SUFFIX}"      CACHE PATH "archive" FORCE)
-set(CMAKE_LINKER       "${ANDROID_NDK_TOOLCHAIN_ROOT}/bin/${ANDROID_TOOLCHAIN_PREFIX}-ld${TOOL_OS_SUFFIX}"      CACHE PATH "linker" FORCE)
-set(CMAKE_NM           "${ANDROID_NDK_TOOLCHAIN_ROOT}/bin/${ANDROID_TOOLCHAIN_PREFIX}-nm${TOOL_OS_SUFFIX}"      CACHE PATH "nm" FORCE)
-set(CMAKE_OBJCOPY      "${ANDROID_NDK_TOOLCHAIN_ROOT}/bin/${ANDROID_TOOLCHAIN_PREFIX}-objcopy${TOOL_OS_SUFFIX}" CACHE PATH "objcopy" FORCE)
-set(CMAKE_OBJDUMP      "${ANDROID_NDK_TOOLCHAIN_ROOT}/bin/${ANDROID_TOOLCHAIN_PREFIX}-objdump${TOOL_OS_SUFFIX}" CACHE PATH "objdump" FORCE)
-set(CMAKE_STRIP        "${ANDROID_NDK_TOOLCHAIN_ROOT}/bin/${ANDROID_TOOLCHAIN_PREFIX}-strip${TOOL_OS_SUFFIX}"   CACHE PATH "strip" FORCE)
-set(CMAKE_RANLIB       "${ANDROID_NDK_TOOLCHAIN_ROOT}/bin/${ANDROID_TOOLCHAIN_PREFIX}-ranlib${TOOL_OS_SUFFIX}"  CACHE PATH "ranlib" FORCE)
-
-if(NDK_CPU_X86)
-	set(ANDROID_NDK_CPU_NAME "x86")
+#
+# Aligned with gluegen/make/scripts/setenv-android-tools.sh
+#
+if(NDK_CPU_X86_64)
+    set(CMAKE_TRY_COMPILE_PLATFORM_VARIABLES ${CMAKE_TRY_COMPILE_PLATFORM_VARIABLES} NDK_CPU_X86_64)
+    set(ANDROID_SYSROOT_ABI "x86_64")
+	set(CMAKE_SYSTEM_PROCESSOR "x86_64")
+    set(ANDROID_TOOLCHAIN_NAME "x86_64-linux-android")
+    set(ANDROID_CLANG_PREFIX ${ANDROID_TOOLCHAIN_NAME})
+    set(ANDROID_LLVM_TRIPLE "x86_64-none-linux-android")
+    message(STATUS "Using NDK_CPU_x86_64, ANDROID_TOOLCHAIN_NAME = ${ANDROID_TOOLCHAIN_NAME}")
+elseif(NDK_CPU_X86)
+    set(CMAKE_TRY_COMPILE_PLATFORM_VARIABLES ${CMAKE_TRY_COMPILE_PLATFORM_VARIABLES} NDK_CPU_X86)
+    set(ANDROID_SYSROOT_ABI "x86")
 	set(CMAKE_SYSTEM_PROCESSOR "x86")
+    set(ANDROID_TOOLCHAIN_NAME "i686-linux-android")
+    set(ANDROID_CLANG_PREFIX ${ANDROID_TOOLCHAIN_NAME})
+    set(ANDROID_LLVM_TRIPLE "i686-none-linux-android")
+    message(STATUS "Using NDK_CPU_X86, ANDROID_TOOLCHAIN_NAME = ${ANDROID_TOOLCHAIN_NAME}")
 elseif(NDK_CPU_ARM64)
-	set(NDK_CPU_ARM true)
-	set(ANDROID_NDK_CPU_NAME "arm64-v8a")
-	set(NDK_CPU_ARM_NEON false)
+    set(CMAKE_TRY_COMPILE_PLATFORM_VARIABLES ${CMAKE_TRY_COMPILE_PLATFORM_VARIABLES} NDK_CPU_ARM64)
+    set(ANDROID_SYSROOT_ABI "arm64")
 	set(CMAKE_SYSTEM_PROCESSOR "armv8-a")
+    set(ANDROID_TOOLCHAIN_NAME "aarch64-linux-android")
+    set(ANDROID_CLANG_PREFIX ${ANDROID_TOOLCHAIN_NAME})
+    set(ANDROID_LLVM_TRIPLE "aarch64-none-linux-android")
+    message(STATUS "Using NDK_CPU_ARM64, ANDROID_TOOLCHAIN_NAME = ${ANDROID_TOOLCHAIN_NAME}")
 elseif(NDK_CPU_ARM_V7A)
-	set(NDK_CPU_ARM_NEON false)
+    set(CMAKE_TRY_COMPILE_PLATFORM_VARIABLES ${CMAKE_TRY_COMPILE_PLATFORM_VARIABLES} NDK_CPU_ARM_V7A)
+	set(NDK_CPU_ARM_NEON true)
 	set(NDK_CPU_ARM_VFPV3 false)
 	set(NDK_CPU_ARM true)
-	set(ANDROID_NDK_CPU_NAME "armeabi-v7a")
+    set(ANDROID_SYSROOT_ABI "arm")
 	set(CMAKE_SYSTEM_PROCESSOR "armv7-a")
-else()
-	set(NDK_CPU_ARM true)
-	set(ANDROID_NDK_CPU_NAME "armeabi")
+    set(ANDROID_TOOLCHAIN_NAME "arm-linux-androideabi")
+    set(ANDROID_CLANG_PREFIX "armv7a-linux-androideabi")
+    set(ANDROID_LLVM_TRIPLE "armv7-none-linux-androideabi")
+    message(STATUS "Using NDK_CPU_ARM, ANDROID_TOOLCHAIN_NAME = ${ANDROID_TOOLCHAIN_NAME}")
+elseif(NDK_CPU_ARM)
+    set(CMAKE_TRY_COMPILE_PLATFORM_VARIABLES ${CMAKE_TRY_COMPILE_PLATFORM_VARIABLES} NDK_CPU_ARM)
 	set(NDK_CPU_ARM_NEON false)
+	set(NDK_CPU_ARM true)
+    set(ANDROID_SYSROOT_ABI "arm")
 	set(CMAKE_SYSTEM_PROCESSOR "armv5te")
+    set(ANDROID_TOOLCHAIN_NAME "arm-linux-androideabi")
+    set(ANDROID_CLANG_PREFIX "armv7a-linux-androideabi")
+    set(ANDROID_LLVM_TRIPLE "armv7-none-linux-androideabi")
+    message(STATUS "Using NDK_CPU_ARM, ANDROID_TOOLCHAIN_NAME = ${ANDROID_TOOLCHAIN_NAME}")
+else()
+    message(FATAL_ERROR "You must define one of NDK_CPU_* [X86_64 X86 ARM64 ARM_V7A ARM]")
 endif()
 
-set(CMAKE_FIND_ROOT_PATH "${ANDROID_NDK_TOOLCHAIN_ROOT}/bin" "${ANDROID_NDK_TOOLCHAIN_ROOT}/${ANDROID_TOOLCHAIN_PREFIX}" "${ANDROID_NDK_SYSROOT}" "${CMAKE_INSTALL_PREFIX}" "${CMAKE_INSTALL_PREFIX}/share")
+set(ANDROID_NDK_TOOLCHAIN_ROOT "${ANDROID_NDK}/toolchains/llvm/prebuilt/${ANDROID_HOST_TAG}")
+set(ANDROID_NDK_SYSROOT0 "${ANDROID_NDK}/platforms/android-${ANDROID_API_LEVEL}/arch-${ANDROID_SYSROOT_ABI}")
+set(ANDROID_NDK_SYSROOT1 "${ANDROID_NDK_TOOLCHAIN_ROOT}/sysroot")
+set(ANDROID_NDK_SYSROOT1_LIB1 "${ANDROID_NDK_SYSROOT1}/usr/lib/${ANDROID_TOOLCHAIN_NAME}/${ANDROID_API_LEVEL}")
+set(ANDROID_NDK_SYSROOT1_LIB2 "${ANDROID_NDK_SYSROOT1}/usr/lib/${ANDROID_TOOLCHAIN_NAME}")
 
-set(STL_PATH "${ANDROID_NDK}/sources/cxx-stl/gnu-libstdc++/${ANDROID_TOOLCHAIN_VERSION}")
-set(STL_LIBRARIES_PATH "${STL_PATH}/libs/${ANDROID_NDK_CPU_NAME}")
-include_directories(SYSTEM "${STL_PATH}/include" "${STL_LIBRARIES_PATH}/include")
-link_directories("${ANDROID_NDK_SYSROOT}/usr/lib")
+set(CMAKE_C_COMPILER   "${ANDROID_NDK_TOOLCHAIN_ROOT}/bin/${ANDROID_CLANG_PREFIX}${ANDROID_API_LEVEL}-clang${TOOL_OS_SUFFIX}"   CACHE PATH "clang" FORCE)
+set(CMAKE_CXX_COMPILER "${ANDROID_NDK_TOOLCHAIN_ROOT}/bin/${ANDROID_CLANG_PREFIX}${ANDROID_API_LEVEL}-clang++${TOOL_OS_SUFFIX}" CACHE PATH "clang++" FORCE)
+set(CMAKE_AR           "${ANDROID_NDK_TOOLCHAIN_ROOT}/bin/${ANDROID_TOOLCHAIN_NAME}-ar${TOOL_OS_SUFFIX}"      CACHE PATH "archive" FORCE)
+set(CMAKE_LINKER       "${ANDROID_NDK_TOOLCHAIN_ROOT}/bin/${ANDROID_TOOLCHAIN_NAME}-ld${TOOL_OS_SUFFIX}"      CACHE PATH "linker" FORCE)
+set(CMAKE_NM           "${ANDROID_NDK_TOOLCHAIN_ROOT}/bin/${ANDROID_TOOLCHAIN_NAME}-nm${TOOL_OS_SUFFIX}"      CACHE PATH "nm" FORCE)
+set(CMAKE_OBJCOPY      "${ANDROID_NDK_TOOLCHAIN_ROOT}/bin/${ANDROID_TOOLCHAIN_NAME}-objcopy${TOOL_OS_SUFFIX}" CACHE PATH "objcopy" FORCE)
+set(CMAKE_OBJDUMP      "${ANDROID_NDK_TOOLCHAIN_ROOT}/bin/${ANDROID_TOOLCHAIN_NAME}-objdump${TOOL_OS_SUFFIX}" CACHE PATH "objdump" FORCE)
+set(CMAKE_STRIP        "${ANDROID_NDK_TOOLCHAIN_ROOT}/bin/${ANDROID_TOOLCHAIN_NAME}-strip${TOOL_OS_SUFFIX}"   CACHE PATH "strip" FORCE)
+set(CMAKE_RANLIB       "${ANDROID_NDK_TOOLCHAIN_ROOT}/bin/${ANDROID_TOOLCHAIN_NAME}-ranlib${TOOL_OS_SUFFIX}"  CACHE PATH "ranlib" FORCE)
 
-set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM BOTH)
-set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
-set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
+set(CMAKE_FIND_ROOT_PATH "${ANDROID_NDK_TOOLCHAIN_ROOT}/bin" "${ANDROID_NDK_TOOLCHAIN_ROOT}/${ANDROID_TOOLCHAIN_NAME}" "${ANDROID_NDK_SYSROOT0}" "${CMAKE_INSTALL_PREFIX}" "${CMAKE_INSTALL_PREFIX}/share")
 
-set(CMAKE_C_FLAGS "-fPIC -DANDROID -Wno-psabi -fsigned-char -I${ANDROID_NDK_SYSROOT}/usr/include")
-set(CMAKE_CXX_FLAGS "-fPIC -DANDROID -Wno-psabi -fsigned-char -I${ANDROID_NDK_SYSROOT}/usr/include")
+# Using llvm's c++_shared as of NDK r18: https://developer.android.com/ndk/guides/cpp-support.html
+# Also see https://github.com/android/ndk/issues/452 and https://gitlab.kitware.com/cmake/cmake/issues/17059
+set(ANDROID_STL "c++_shared")
+set(STL_INCLUDE_PATH0 "${ANDROID_NDK_SYSROOT1}/usr/include/c++/v1")
+include_directories(BEFORE SYSTEM "${STL_INCLUDE_PATH0}")
 
-set(FORCE_ARM OFF CACHE BOOL "Use 32-bit ARM instructions instead of Thumb-1")
-if(NDK_CPU_X86)
-elseif(NDK_CPU_ARM64)
-	set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -march=armv8-a -std=c99")
-elseif(NOT FORCE_ARM)
-	set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -mthumb")
-else()
-	set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -marm")
-endif()
+set(OPENSL_INCLUDE_DIR "${ANDROID_NDK_SYSROOT1}/usr/include")
+set(OPENSL_ANDROID_INCLUDE_DIR "${ANDROID_NDK_SYSROOT1}/usr/include")
+set(OPENSL_LIBRARY "${ANDROID_NDK_SYSROOT0}/usr/lib/libOpenSLES.so")
 
-set(CMAKE_C_FLAGS "--sysroot=${ANDROID_NDK_SYSROOT} ${CMAKE_C_FLAGS}")
+link_directories("${ANDROID_NDK_SYSROOT0}/usr/lib")
 
-include(CMakeForceCompiler)
-CMAKE_FORCE_C_COMPILER("${CMAKE_C_COMPILER}" GNU)
-CMAKE_FORCE_CXX_COMPILER("${CMAKE_CXX_COMPILER}" GNU)
+set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM BOTH)
+set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
+set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
 
-if(NDK_CPU_ARM_V7A)
-	set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -march=armv7-a -mfloat-abi=softfp")
-	if(NDK_CPU_ARM_NEON)
-		set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -mfpu=neon")
-	elseif(NDK_CPU_ARM_VFPV3)
-		set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -mfpu=vfpv3")
-	endif()
-elseif(NDK_CPU_ARM64)
-	set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -mabi=lp64 -mlittle-endian -march=armv8-a -std=c99")
+set(CMAKE_C_FLAGS "-nostdinc++ -fPIC -DANDROID -fsigned-char")
+#set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -v")
+
+# from sdk cmake start
+#   <compilerarg value="-fdata-sections" />
+#   <compilerarg value="-ffunction-sections" />
+#   <compilerarg value="-funwind-tables" />
+#   <compilerarg value="-fstack-protector-strong" />
+#   <compilerarg value="-no-canonical-prefixes" />
+
+set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -target ${ANDROID_LLVM_TRIPLE}")
+if(NDK_CPU_ARM_NEON)
+    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -mfpu=neon")
+elseif(NDK_CPU_ARM_VFPV3)
+    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -mfpu=vfpv3")
 endif()
 
-set(CMAKE_CXX_FLAGS "${CMAKE_C_FLAGS}" CACHE STRING "c++ flags")
+# Using llvm's c++_shared as of NDK r18: https://developer.android.com/ndk/guides/cpp-support.html
+# Also see https://github.com/android/ndk/issues/452 and https://gitlab.kitware.com/cmake/cmake/issues/17059
+set(CMAKE_CXX_FLAGS "${CMAKE_C_FLAGS} -isystem ${STL_INCLUDE_PATH0} -isystem ${ANDROID_NDK_SYSROOT1}/usr/include -isystem ${ANDROID_NDK_SYSROOT1}/usr/include/${ANDROID_TOOLCHAIN_NAME}")
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}" CACHE STRING "c++ flags")
+
+#set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} --sysroot=${ANDROID_NDK_SYSROOT1} -isysroot ${ANDROID_NDK_SYSROOT1} -isystem ${ANDROID_NDK_SYSROOT1}/usr/include -isystem ${ANDROID_NDK_SYSROOT1}/usr/include/${ANDROID_TOOLCHAIN_NAME}")
+set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -isystem ${ANDROID_NDK_SYSROOT1}/usr/include -isystem ${ANDROID_NDK_SYSROOT1}/usr/include/${ANDROID_TOOLCHAIN_NAME}")
 set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS}" CACHE STRING "c flags")
       
 message(STATUS "CMAKE_C_COMPILER  : ${CMAKE_C_COMPILER}")
@@ -181,7 +180,8 @@ message(STATUS "CMAKE_CXX_FLAGS: ${CMAKE_CXX_FLAGS}")
 message(STATUS "NDK_CPU_ARM: ${NDK_CPU_ARM}")
 message(STATUS "NDK_CPU_ARM64: ${NDK_CPU_ARM64}")
 
-set(LINKER_FLAGS "-L\"${STL_LIBRARIES_PATH}\" -L\"${CMAKE_INSTALL_PREFIX}/libs/${ANDROID_NDK_CPU_NAME}\"")
+set(LINKER_FLAGS "--sysroot=${ANDROID_NDK_SYSROOT0} -L\"${ANDROID_NDK_SYSROOT1_LIB1}\" -Wl,-rpath-link=\"${ANDROID_NDK_SYSROOT1_LIB1}\" -L\"${ANDROID_NDK_SYSROOT1_LIB2}\" -target ${ANDROID_LLVM_TRIPLE}")
+#set(LINKER_FLAGS "${LINKER_FLAGS} -v")
 
 message(STATUS "ARM32_LINKER_OPTS: ${ARM32_LINKER_OPTS}")
 message(STATUS "ARM64_LINKER_OPTS: ${ARM64_LINKER_OPTS}")
@@ -198,6 +198,7 @@ endif()
 
 message(STATUS "LINKER_FLAGS: ${LINKER_FLAGS}")
 
+# Requires CMake >= 3.2.0 to have these flags being honored by try_compile()
 set(CMAKE_SHARED_LINKER_FLAGS "${LINKER_FLAGS}" CACHE STRING "shared linker flags" FORCE)
 set(CMAKE_MODULE_LINKER_FLAGS "${LINKER_FLAGS}" CACHE STRING "module linker flags" FORCE)
 set(CMAKE_EXE_LINKER_FLAGS "${LINKER_FLAGS}" CACHE STRING "exe linker flags" FORCE)
@@ -206,8 +207,10 @@ message(STATUS "CMAKE_SHARED_LINKER_FLAGS: ${CMAKE_SHARED_LINKER_FLAGS}")
 message(STATUS "CMAKE_MODULE_LINKER_FLAGS: ${CMAKE_MODULE_LINKER_FLAGS}")
 message(STATUS "CMAKE_EXE_LINKER_FLAGS: ${CMAKE_EXE_LINKER_FLAGS}")
 message(STATUS "CMAKE_STATIC_LINKER_FLAGS: ${CMAKE_STATIC_LINKER_FLAGS}")
+message(STATUS "CMAKE_CXX_LINK_EXECUTABLE: ${CMAKE_CXX_LINK_EXECUTABLE}")
+message(STATUS "CMAKE_C_LINK_EXECUTABLE: ${CMAKE_C_LINK_EXECUTABLE}")
+message(STATUS "CMAKE_LINK_EXECUTABLE: ${CMAKE_LINK_EXECUTABLE}")
+message(STATUS "CMAKE_TRY_COMPILE_PLATFORM_VARIABLES: ${CMAKE_TRY_COMPILE_PLATFORM_VARIABLES}")
 
 set(ANDROID true)
 set(BUILD_ANDROID true)
-
-MARK_AS_ADVANCED(FORCE_ARM NO_UNDEFINED)