How to compile FFmpeg for Android with clang in ub

Question

I want to compile FFmpeg with clang as it's more faster,but I don't know how to do it in ubuntu. NDk version r16b ,ffmpeg version 4.1.

I did it with gcc. here is my build script,and it works well.

#!/bin/sh
NDK=/home/gjy/ndk/android-ndk-r16b-linux-x86_64/android-ndk-r16b
ANDROID_VERSION=19
TOOLCHAIN_VERSION=4.9
BUILD_PLATFORM=linux-x86_64
ARCH=arm
ANDROID_ARCH_ABI=armeabi
HOST=arm-linux-androideabi
CROSS=arm-linux-androideabi
SYSROOT=${NDK}/platforms/android-${ANDROID_VERSION}/arch-${ARCH}/
PREFIX=$(pwd)/android/${ANDROID_VERSION}/$ANDROID_ARCH_ABI
TOOLCHAIN=${NDK}/toolchains/${HOST}-${TOOLCHAIN_VERSION}/prebuilt/${BUILD_PLATFORM}
CFLAGS="-Os -fpic -march=armv5te -isysroot $NDK/sysroot -I$NDK/sysroot/usr/include/$CROSS -D__ANDROID_API__=$ANDROID_VERSION -U_FILE_OFFSET_BITS"
CROSS_PREFIX=${TOOLCHAIN}/bin/${CROSS}-
build(){
echo "configuring $ANDROID_ARCH_ABI ANDROID_VERSION=$ANDROID_VERSION"
./configure \
    --prefix=$PREFIX \
    --enable-neon \
    --enable-hwaccels \
    --enable-gpl \
    --enable-postproc \
    --enable-shared \
    --enable-jni \
    --enable-mediacodec \
    --enable-decoder=h264_mediacodec \
    --enable-hwaccel=h264_mediacodec \
    --enable-decoder=hevc_mediacodec \
    --enable-decoder=mpeg4_mediacodec \
    --enable-decoder=vp8_mediacodec \
    --enable-decoder=vp9_mediacodec \
    --disable-static \
    --disable-doc \
    --enable-ffmpeg \
    --disable-ffplay \
    --disable-ffprobe \
    --enable-avdevice \
    --disable-doc \
    --disable-symver \
    --cross-prefix=$CROSS_PREFIX \
    --target-os=android \
    --arch=$ARCH \
    --disable-yasm \
    --enable-cross-compile \
    --sysroot=$SYSROOT \
    --extra-cflags="$CFLAGS " \
    --extra-ldflags="$ADDI_LDFLAGS" \
    $ADDITIONAL_CONFIGURE_FLAG
    make clean
    make -j4
    make install
    echo "$ANDROID_ARCH_ABI installed"
}
build

I wonder how to do it with clang friendly.I'm still new int the NDK and I've just started learning.So I have no idea to do it at all. When I was trying turn to clang,and get many errors. After trying so many times,I update my build script with this question:

FFMPEG source compilation failed with Android NDK Clang compiler (r16b) with error "the clang compiler does not support '-mcpu=arm'"

#!/bin/sh
#r16b min support android-14  max android-8.1
NDK=/home/gjy/ndk/android-ndk-r16b-linux-x86_64/android-ndk-r16b
ANDROID_VERSION=19
TOOLCHAIN_VERSION=4.9
BUILD_PLATFORM=linux-x86_64
ARCH=arm
ANDROID_ARCH_ABI=armeabi
HOST=arm-linux-androideabi
CROSS=arm-linux-androideabi
SYSROOT=${NDK}/platforms/android-${ANDROID_VERSION}/arch-${ARCH}/
PREFIX=$(pwd)/android/${ANDROID_VERSION}/$ANDROID_ARCH_ABI
TOOLCHAIN=${NDK}/toolchains/llvm/prebuilt/${BUILD_PLATFORM}/bin
#LD
LD=${NDK}/toolchains/${HOST}-${TOOLCHAIN_VERSION}/prebuilt/${BUILD_PLATFORM}/bin/${CROSS}-ld
#AS
AS=${NDK}/toolchains/${HOST}-${TOOLCHAIN_VERSION}/prebuilt/${BUILD_PLATFORM}/bin/${CROSS}-as
#AR
AR=${NDK}/toolchains/${HOST}-${TOOLCHAIN_VERSION}/prebuilt/${BUILD_PLATFORM}/bin/${CROSS}-ar
CFLAGS="-mcpu=$ARCH -I$NDK/sysroot/usr/include/$CROSS -D__ANDROID_API__=$ANDROID_VERSION"
CROSS_PREFIX=${NDK}/toolchains/${HOST}-${TOOLCHAIN_VERSION}/prebuilt/${BUILD_PLATFORM}/bin/${CROSS}-
build(){
echo "configuring $ANDROID_ARCH_ABI ANDROID_VERSION=$ANDROID_VERSION"
./configure \
    --prefix=$PREFIX \
    --toolchain=clang-usan \
    --cross-prefix=$CROSS_PREFIX \
    --enable-neon \
    --enable-hwaccels \
    --enable-gpl \
    --enable-postproc \
    --enable-shared \
    --disable-static \
    --enable-jni \
    --enable-mediacodec \
    --enable-decoder=h264_mediacodec \
    --enable-hwaccel=h264_mediacodec \
    --enable-decoder=hevc_mediacodec \
    --enable-decoder=mpeg4_mediacodec \
    --enable-decoder=vp8_mediacodec \
    --enable-decoder=vp9_mediacodec \
    --disable-doc \
    --enable-ffmpeg \
    --disable-ffplay \
    --disable-ffprobe \
    --enable-avdevice \
    --disable-doc \
    --disable-symver \
    --target-os=android \
    --extra-ldflags="-shared" \
    --arch=$ARCH \
    --cpu=$ANDROID_ARCH_ABI \
    --extra-cflags="-fPIE -fPIC -ffast-math -funroll-loops -mfloat-abi=softfp -mfpu=vfpv3-d16" \
    --enable-x86asm \
    --enable-cross-compile \
    --cc=$TOOLCHAIN/clang \
    --cxx=$TOOLCHAIN/clang++ \
    --ld=$LD \
    --as=$AS \
    --ar=$AR \
    --strip=${NDK}/toolchains/${HOST}-${TOOLCHAIN_VERSION}/prebuilt/${BUILD_PLATFORM}/${CROSS}-strip \
    $ADDITIONAL_CONFIGURE_FLAG
    #make clean
    #make -j4
    #make install
    echo "$ANDROID_ARCH_ABI installed"
}
build

then I get error form config.log :

/home/gjy/ndk/android-ndk-r16b-linux-x86_64/android-ndk-r16b/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/arm-linux-androideabi-as -D_ISOC99_SOURCE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_POSIX_C_SOURCE=200112 -D_XOPEN_SOURCE=600 -DPIC -fPIE -fPIC -ffast-math -funroll-loops -mfloat-abi=softfp -mfpu=vfpv3-d16 -mcpu=armeabi -fPIC -c -o /tmp/ffconf.hfTGr6sO/test.o /tmp/ffconf.hfTGr6sO/test.S
/home/gjy/ndk/android-ndk-r16b-linux-x86_64/android-ndk-r16b/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/arm-linux-androideabi-as: invalid option -- '_'
GNU assembler not found, install/update gas-preprocessor

it seems like that the frist char was ignored. When I try :

/home/gjy/ndk/android-ndk-r16b-linux-x86_64/android-ndk-r16b/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/arm-linux-androideabi-as -fPIC -c -o /tmp/ffconf.jHtqLsFE/test.o /tmp/ffconf.jHtqLsFE/test.S
invalid option -- P

can any body help fine the problem？

Answer 1

You must add --as=$TOOLCHAIN/clang parameter into your configure string for compiling assembler code with clang.