BUILDING.md: Update/simplify Android build instr.

Use the android.toolchain.cmake toolchain file in the NDK (v13b or
later), since this toolchain file generally takes care of setting the
approprate compiler flags and dealing with the differences between
GCC and Clang.  Our custom Android build procedure did not work with
Clang-based NDK toolchains, which meant that it could not be made to
work with NDK v18b or later.

Fixes #309

diff --git a/BUILDING.md b/BUILDING.md
index 5dbafd86bfe7efc4a7be8fa8fd7348341e025106..9ef1f45e98d21624b628273961373e48e93f8178 100644 (file)
--- a/BUILDING.md
+++ b/BUILDING.md
@@ -525,7 +525,7 @@ a universal library.
 Building libjpeg-turbo for Android
 ----------------------------------
 
-Building libjpeg-turbo for Android platforms requires the
+Building libjpeg-turbo for Android platforms requires v13b or later of the
 [Android NDK](https://developer.android.com/tools/sdk/ndk).
 
 
@@ -535,35 +535,21 @@ The following is a general recipe script that can be modified for your specific
 needs.
 
     # Set these variables to suit your needs
-    NDK_PATH={full path to the "ndk" directory-- for example, /opt/android/sdk/ndk-bundle}
-    BUILD_PLATFORM={the platform name for the NDK package you installed--
-      for example, "windows-x86" or "linux-x86_64" or "darwin-x86_64"}
-    TOOLCHAIN_VERSION={"4.8", "4.9", "clang3.5", etc.  This corresponds to a
-      toolchain directory under ${NDK_PATH}/toolchains/.}
-    ANDROID_VERSION={The minimum version of Android to support-- for example,
+    NDK_PATH={full path to the NDK directory-- for example,
+      /opt/android/android-ndk-r16b}
+    TOOLCHAIN={"gcc" or "clang"-- "gcc" must be used with NDK r16b and earlier,
+      and "clang" must be used with NDK r17c and later}
+    ANDROID_VERSION={the minimum version of Android to support-- for example,
       "16", "19", etc.}
 
-    # It should not be necessary to modify the rest
-    HOST=arm-linux-androideabi
-    SYSROOT=${NDK_PATH}/platforms/android-${ANDROID_VERSION}/arch-arm
-    export CFLAGS="-march=armv7-a -mfloat-abi=softfp -fprefetch-loop-arrays \
-      -D__ANDROID_API__=${ANDROID_VERSION} --sysroot=${SYSROOT} \
-      -isystem ${NDK_PATH}/sysroot/usr/include \
-      -isystem ${NDK_PATH}/sysroot/usr/include/${HOST}"
-    export LDFLAGS=-pie
-    TOOLCHAIN=${NDK_PATH}/toolchains/${HOST}-${TOOLCHAIN_VERSION}/prebuilt/${BUILD_PLATFORM}
-
     cd {build_directory}
-
-    cat <<EOF >toolchain.cmake
-    set(CMAKE_SYSTEM_NAME Linux)
-    set(CMAKE_SYSTEM_PROCESSOR arm)
-    set(CMAKE_C_COMPILER ${TOOLCHAIN}/bin/${HOST}-gcc)
-    set(CMAKE_FIND_ROOT_PATH ${TOOLCHAIN}/${HOST})
-    EOF
-
-    cmake -G"Unix Makefiles" -DCMAKE_TOOLCHAIN_FILE=toolchain.cmake \
-      -DCMAKE_POSITION_INDEPENDENT_CODE=1 \
+    cmake -G"Unix Makefiles" \
+      -DANDROID_ABI=armeabi-v7a \
+      -DANDROID_ARM_MODE=arm \
+      -DANDROID_PLATFORM=android-${ANDROID_VERSION} \
+      -DANDROID_TOOLCHAIN=${TOOLCHAIN} \
+      -DCMAKE_ASM_FLAGS="--target=arm-linux-androideabi${ANDROID_VERSION}" \
+      -DCMAKE_TOOLCHAIN_FILE=${NDK_PATH}/build/cmake/android.toolchain.cmake \
       [additional CMake flags] {source_directory}
     make
 
@@ -574,34 +560,21 @@ The following is a general recipe script that can be modified for your specific
 needs.
 
     # Set these variables to suit your needs
-    NDK_PATH={full path to the "ndk" directory-- for example, /opt/android/sdk/ndk-bundle}
-    BUILD_PLATFORM={the platform name for the NDK package you installed--
-      for example, "windows-x86" or "linux-x86_64" or "darwin-x86_64"}
-    TOOLCHAIN_VERSION={"4.8", "4.9", "clang3.5", etc.  This corresponds to a
-      toolchain directory under ${NDK_PATH}/toolchains/.}
-    ANDROID_VERSION={The minimum version of Android to support.  "21" or later
+    NDK_PATH={full path to the NDK directory-- for example,
+      /opt/android/android-ndk-r16b}
+    TOOLCHAIN={"gcc" or "clang"-- "gcc" must be used with NDK r14b and earlier,
+      and "clang" must be used with NDK r17c and later}
+    ANDROID_VERSION={the minimum version of Android to support.  "21" or later
       is required for a 64-bit build.}
 
-    # It should not be necessary to modify the rest
-    HOST=aarch64-linux-android
-    SYSROOT=${NDK_PATH}/platforms/android-${ANDROID_VERSION}/arch-arm64
-    export CFLAGS="-D__ANDROID_API__=${ANDROID_VERSION} --sysroot=${SYSROOT} \
-      -isystem ${NDK_PATH}/sysroot/usr/include \
-      -isystem ${NDK_PATH}/sysroot/usr/include/${HOST}"
-    export LDFLAGS=-pie
-    TOOLCHAIN=${NDK_PATH}/toolchains/${HOST}-${TOOLCHAIN_VERSION}/prebuilt/${BUILD_PLATFORM}
-
     cd {build_directory}
-
-    cat <<EOF >toolchain.cmake
-    set(CMAKE_SYSTEM_NAME Linux)
-    set(CMAKE_SYSTEM_PROCESSOR aarch64)
-    set(CMAKE_C_COMPILER ${TOOLCHAIN}/bin/${HOST}-gcc)
-    set(CMAKE_FIND_ROOT_PATH ${TOOLCHAIN}/${HOST})
-    EOF
-
-    cmake -G"Unix Makefiles" -DCMAKE_TOOLCHAIN_FILE=toolchain.cmake \
-      -DCMAKE_POSITION_INDEPENDENT_CODE=1 \
+    cmake -G"Unix Makefiles" \
+      -DANDROID_ABI=arm64-v8a \
+      -DANDROID_ARM_MODE=arm \
+      -DANDROID_PLATFORM=android-${ANDROID_VERSION} \
+      -DANDROID_TOOLCHAIN=${TOOLCHAIN} \
+      -DCMAKE_ASM_FLAGS="--target=aarch64-linux-android${ANDROID_VERSION}" \
+      -DCMAKE_TOOLCHAIN_FILE=${NDK_PATH}/build/cmake/android.toolchain.cmake \
       [additional CMake flags] {source_directory}
     make
 
@@ -612,34 +585,19 @@ The following is a general recipe script that can be modified for your specific
 needs.
 
     # Set these variables to suit your needs
-    NDK_PATH={full path to the "ndk" directory-- for example, /opt/android/sdk/ndk-bundle}
-    BUILD_PLATFORM={the platform name for the NDK package you installed--
-      for example, "windows-x86" or "linux-x86_64" or "darwin-x86_64"}
-    TOOLCHAIN_VERSION={"4.8", "4.9", "clang3.5", etc.  This corresponds to a
-      toolchain directory under ${NDK_PATH}/toolchains/.}
+    NDK_PATH={full path to the NDK directory-- for example,
+      /opt/android/android-ndk-r16b}
+    TOOLCHAIN={"gcc" or "clang"-- "gcc" must be used with NDK r14b and earlier,
+      and "clang" must be used with NDK r17c and later}
     ANDROID_VERSION={The minimum version of Android to support-- for example,
       "16", "19", etc.}
 
-    # It should not be necessary to modify the rest
-    HOST=i686-linux-android
-    SYSROOT=${NDK_PATH}/platforms/android-${ANDROID_VERSION}/arch-x86
-    export CFLAGS="-D__ANDROID_API__=${ANDROID_VERSION} --sysroot=${SYSROOT} \
-      -isystem ${NDK_PATH}/sysroot/usr/include \
-      -isystem ${NDK_PATH}/sysroot/usr/include/${HOST}"
-    export LDFLAGS=-pie
-    TOOLCHAIN=${NDK_PATH}/toolchains/x86-${TOOLCHAIN_VERSION}/prebuilt/${BUILD_PLATFORM}
-
     cd {build_directory}
-
-    cat <<EOF >toolchain.cmake
-    set(CMAKE_SYSTEM_NAME Linux)
-    set(CMAKE_SYSTEM_PROCESSOR i386)
-    set(CMAKE_C_COMPILER ${TOOLCHAIN}/bin/${HOST}-gcc)
-    set(CMAKE_FIND_ROOT_PATH ${TOOLCHAIN}/${HOST})
-    EOF
-
-    cmake -G"Unix Makefiles" -DCMAKE_TOOLCHAIN_FILE=toolchain.cmake \
-      -DCMAKE_POSITION_INDEPENDENT_CODE=1 \
+    cmake -G"Unix Makefiles" \
+      -DANDROID_ABI=x86 \
+      -DANDROID_PLATFORM=android-${ANDROID_VERSION} \
+      -DANDROID_TOOLCHAIN=${TOOLCHAIN} \
+      -DCMAKE_TOOLCHAIN_FILE=${NDK_PATH}/build/cmake/android.toolchain.cmake \
       [additional CMake flags] {source_directory}
     make
 
@@ -650,45 +608,23 @@ The following is a general recipe script that can be modified for your specific
 needs.
 
     # Set these variables to suit your needs
-    NDK_PATH={full path to the "ndk" directory-- for example, /opt/android/sdk/ndk-bundle}
-    BUILD_PLATFORM={the platform name for the NDK package you installed--
-      for example, "windows-x86" or "linux-x86_64" or "darwin-x86_64"}
-    TOOLCHAIN_VERSION={"4.8", "4.9", "clang3.5", etc.  This corresponds to a
-      toolchain directory under ${NDK_PATH}/toolchains/.}
-    ANDROID_VERSION={The minimum version of Android to support.  "21" or later
+    NDK_PATH={full path to the NDK directory-- for example,
+      /opt/android/android-ndk-r16b}
+    TOOLCHAIN={"gcc" or "clang"-- "gcc" must be used with NDK r14b and earlier,
+      and "clang" must be used with NDK r17c and later}
+    ANDROID_VERSION={the minimum version of Android to support.  "21" or later
       is required for a 64-bit build.}
 
-    # It should not be necessary to modify the rest
-    HOST=x86_64-linux-android
-    SYSROOT=${NDK_PATH}/platforms/android-${ANDROID_VERSION}/arch-x86_64
-    export CFLAGS="-D__ANDROID_API__=${ANDROID_VERSION} --sysroot=${SYSROOT} \
-      -isystem ${NDK_PATH}/sysroot/usr/include \
-      -isystem ${NDK_PATH}/sysroot/usr/include/${HOST}"
-    export LDFLAGS=-pie
-    TOOLCHAIN=${NDK_PATH}/toolchains/x86_64-${TOOLCHAIN_VERSION}/prebuilt/${BUILD_PLATFORM}
-
     cd {build_directory}
-
-    cat <<EOF >toolchain.cmake
-    set(CMAKE_SYSTEM_NAME Linux)
-    set(CMAKE_SYSTEM_PROCESSOR x86_64)
-    set(CMAKE_C_COMPILER ${TOOLCHAIN}/bin/${HOST}-gcc)
-    set(CMAKE_FIND_ROOT_PATH ${TOOLCHAIN}/${HOST})
-    EOF
-
-    cmake -G"Unix Makefiles" -DCMAKE_TOOLCHAIN_FILE=toolchain.cmake \
-      -DCMAKE_POSITION_INDEPENDENT_CODE=1 \
+    cmake -G"Unix Makefiles" \
+      -DANDROID_ABI=x86_64 \
+      -DANDROID_PLATFORM=android-${ANDROID_VERSION} \
+      -DANDROID_TOOLCHAIN=${TOOLCHAIN} \
+      -DCMAKE_TOOLCHAIN_FILE=${NDK_PATH}/build/cmake/android.toolchain.cmake \
       [additional CMake flags] {source_directory}
     make
 
 
-If building for Android 4.0.x (API level < 16) or earlier, remove
-`-DCMAKE_POSITION_INDEPENDENT_CODE=1` from the CMake arguments and `-pie` from
-`LDFLAGS`.
-
-If building on Windows, add `.exe` to the end of `CMAKE_C_COMPILER`.
-
-
 Advanced CMake Options
 ----------------------