configure

    echo "$1" > $TMPS
    log_file $TMPS
    shift 1
    check_cmd $x86asmexe $X86ASMFLAGS -Werror "$@" -o $TMPO $TMPS
}

ld_o(){
    eval printf '%s\\n' $LD_O
}

check_ld(){
    log check_ld "$@"
    type=$1
    shift 1
    flags=$(filter_out '-l*|*.so' $@)
    libs=$(filter '-l*|*.so' $@)
    check_$type $($cflags_filter $flags) || return
    flags=$($ldflags_filter $flags)
    libs=$($ldflags_filter $libs)
    check_cmd $ld $LDFLAGS $LDEXEFLAGS $flags $(ld_o $TMPE) $TMPO $libs $extralibs
}

print_include(){
    hdr=$1
    test "${hdr%.h}" = "${hdr}" &&
        echo "#include $hdr"    ||
        echo "#include <$hdr>"
}

check_code(){
    log check_code "$@"
    check=$1
    headers=$2
    code=$3
    shift 3
    {
        for hdr in $headers; do
            print_include $hdr
        done
        echo "int main(void) { $code; return 0; }"
    } | check_$check "$@"
}

check_cppflags(){
    log check_cppflags "$@"
    check_cpp "$@" <<EOF && append CPPFLAGS "$@"
#include <stdlib.h>
EOF
}

test_cflags(){
    log test_cflags "$@"
    set -- $($cflags_filter "$@")
    check_cc "$@" <<EOF
int x;
EOF
}

check_cflags(){
    log check_cflags "$@"
    test_cflags "$@" && add_cflags "$@"
}

check_cxxflags(){
    log check_cxxflags "$@"
    set -- $($cflags_filter "$@")
    check_cxx "$@" <<EOF && append CXXFLAGS "$@"
int x;
EOF
}

test_objcflags(){
    log test_objcflags "$@"
    set -- $($objcflags_filter "$@")
    check_objcc "$@" <<EOF
int x;
EOF
}

check_objcflags(){
    log check_objcflags "$@"
    test_objcflags "$@" && add_objcflags "$@"
}

test_ldflags(){
    log test_ldflags "$@"
    set -- $($ldflags_filter "$@")
    check_ld "cc" "$@" <<EOF
int main(void){ return 0; }
EOF
}

check_ldflags(){
    log check_ldflags "$@"
    test_ldflags "$@" && add_ldflags "$@"
}

test_stripflags(){
    log test_stripflags "$@"
    # call check_cc to get a fresh TMPO
    check_cc <<EOF
int main(void) { return 0; }
EOF
    check_cmd $strip $ASMSTRIPFLAGS "$@" $TMPO
}

check_stripflags(){
    log check_stripflags "$@"
    test_stripflags "$@" && add_stripflags "$@"
}

check_header(){
    log check_header "$@"
    headers=$1
    shift
    disable_sanitized $headers
    {
        for hdr in $headers; do
            print_include $hdr
        done
        echo "int x;"
    } | check_cpp "$@" && enable_sanitized $headers
}

check_header_objcc(){
    log check_header_objcc "$@"
    rm -f -- "$TMPO"
    header=$1
    shift
    disable_sanitized $header
    {
       echo "#include <$header>"
       echo "int main(void) { return 0; }"
    } | check_objcc && check_stat "$TMPO" && enable_sanitized $header
}

check_apple_framework(){
    log check_apple_framework "$@"
    framework="$1"
    name="$(tolower $framework)"
    header="${framework}/${framework}.h"
    disable $name
    check_header_objcc $header &&
        enable $name && eval ${name}_extralibs='"-framework $framework"'
}

check_func(){
    log check_func "$@"
    func=$1
    shift
    disable $func
    check_ld "cc" "$@" <<EOF && enable $func
extern int $func();
int main(void){ $func(); }
EOF
}

check_complexfunc(){
    log check_complexfunc "$@"
    func=$1
    narg=$2
    shift 2
    test $narg = 2 && args="f, g" || args="f * I"
    disable $func
    check_ld "cc" "$@" <<EOF && enable $func
#include <complex.h>
#include <math.h>
float foo(complex float f, complex float g) { return $func($args); }
int main(void){ return (int) foo; }
EOF
}

check_mathfunc(){
    log check_mathfunc "$@"
    func=$1
    narg=$2
    shift 2
    test $narg = 2 && args="f, g" || args="f"
    disable $func
    check_ld "cc" "$@" <<EOF && enable $func
#include <math.h>
float foo(float f, float g) { return $func($args); }
int main(void){ return (int) foo; }
EOF
}

check_func_headers(){
    log check_func_headers "$@"
    headers=$1
    funcs=$2
    shift 2
    {
        for hdr in $headers; do
            print_include $hdr
        done
        echo "#include <stdint.h>"
        for func in $funcs; do
            echo "long check_$func(void) { return (long) $func; }"
        done
        echo "int main(void) { int ret = 0;"
        # LTO could optimize out the test functions without this
        for func in $funcs; do
            echo " ret |= ((intptr_t)check_$func) & 0xFFFF;"
        done
        echo "return ret; }"
    } | check_ld "cc" "$@" && enable $funcs && enable_sanitized $headers
}

check_class_headers_cpp(){
    log check_class_headers_cpp "$@"
    headers=$1
    classes=$2
    shift 2
    {
        for hdr in $headers; do
            echo "#include <$hdr>"
        done
        echo "int main(void) { "
        i=1
        for class in $classes; do
            echo "$class obj$i;"
            i=$(expr $i + 1)
        done
        echo "return 0; }"
    } | check_ld "cxx" "$@" && enable $funcs && enable_sanitized $headers
}

check_cpp_condition(){
    log check_cpp_condition "$@"
    header=$1
    condition=$2
    shift 2
    check_cpp "$@" <<EOF
#include <$header>
#if !($condition)
#error "unsatisfied condition: $condition"
#endif
EOF
}

test_cflags_cc(){
    log test_cflags_cc "$@"
    flags=$1
    header=$2
    condition=$3
    shift 3
    set -- $($cflags_filter "$flags")
    check_cc "$@" <<EOF
#include <$header>
#if !($condition)
#error "unsatisfied condition: $condition"
#endif
EOF
}

check_lib(){
    log check_lib "$@"
    name="$1"
    headers="$2"
    funcs="$3"
    shift 3
    disable $name
    check_func_headers "$headers" "$funcs" "$@" &&
        enable $name && eval ${name}_extralibs="\$@"
}

check_lib_cpp(){
    log check_lib_cpp "$@"
    name="$1"
    headers="$2"
    classes="$3"
    shift 3
    disable $name
    check_class_headers_cpp "$headers" "$classes" "$@" &&
        enable $name && eval ${name}_extralibs="\$@"
}

test_pkg_config(){
    log test_pkg_config "$@"
    name="$1"
    pkg_version="$2"
    pkg="${2%% *}"
    headers="$3"
    funcs="$4"
    shift 4
    disable $name
    check_cmd $pkg_config --exists --print-errors $pkg_version || return
    pkg_cflags=$($pkg_config --cflags $pkg_config_flags $pkg)
    pkg_libs=$($pkg_config --libs $pkg_config_flags $pkg)
    check_func_headers "$headers" "$funcs" $pkg_cflags $pkg_libs "$@" &&
        enable $name &&
        set_sanitized "${name}_cflags"    $pkg_cflags &&
        set_sanitized "${name}_extralibs" $pkg_libs
}

check_pkg_config(){
    log check_pkg_config "$@"
    name="$1"
    test_pkg_config "$@" &&
        eval add_cflags \$${name}_cflags
}

check_exec(){
    check_ld "cc" "$@" && { enabled cross_compile || $TMPE >> $logfile 2>&1; }
}

check_exec_crash(){
    log check_exec_crash "$@"
    code=$(cat)

    # exit() is not async signal safe.  _Exit (C99) and _exit (POSIX)
    # are safe but may not be available everywhere.  Thus we use
    # raise(SIGTERM) instead.  The check is run in a subshell so we
    # can redirect the "Terminated" message from the shell.  SIGBUS
    # is not defined by standard C so it is used conditionally.

    (check_exec "$@") >> $logfile 2>&1 <<EOF
#include <signal.h>
static void sighandler(int sig){
    raise(SIGTERM);
}
int foo(void){
    $code
}
int (*func_ptr)(void) = foo;
int main(void){
    signal(SIGILL, sighandler);
    signal(SIGFPE, sighandler);
    signal(SIGSEGV, sighandler);
#ifdef SIGBUS
    signal(SIGBUS, sighandler);
#endif
    return func_ptr();
}
EOF
}

check_type(){
    log check_type "$@"
    headers=$1
    type=$2
    shift 2
    disable_sanitized "$type"
    check_code cc "$headers" "$type v" "$@" && enable_sanitized "$type"
}

check_struct(){
    log check_struct "$@"
    headers=$1
    struct=$2
    member=$3
    shift 3
    disable_sanitized "${struct}_${member}"
    check_code cc "$headers" "const void *p = &(($struct *)0)->$member" "$@" &&
        enable_sanitized "${struct}_${member}"
}

check_builtin(){
    log check_builtin "$@"
    name=$1
    headers=$2
    builtin=$3
    shift 3
    disable "$name"
    check_code ld "$headers" "$builtin" "cc" "$@" && enable "$name"
}

check_compile_assert(){
    log check_compile_assert "$@"
    name=$1
    headers=$2
    condition=$3
    shift 3
    disable "$name"
    check_code cc "$headers" "char c[2 * !!($condition) - 1]" "$@" && enable "$name"
}

require(){
    log require "$@"
    name_version="$1"
    name="${1%% *}"
    headers="$2"
    func="$3"
    shift 3
    check_lib $name "$headers" $func "$@" || die "ERROR: $name_version not found"
}

require_cpp(){
    name="$1"
    headers="$2"
    classes="$3"
    shift 3
    check_lib_cpp "$headers" "$classes" "$@" || die "ERROR: $name not found"
}

require_header(){
    log require_header "$@"
    headers="$1"
    shift
    check_header "$headers" "$@" || die "ERROR: $headers not found"
}

require_cpp_condition(){
    log require_cpp_condition "$@"
    header="$1"
    condition="$2"
    shift 2
    check_cpp_condition "$header" "$condition" "$@" || die "ERROR: $condition not satisfied"
}

require_pkg_config(){
    log require_pkg_config "$@"
    pkg_version="$2"
    check_pkg_config "$@" || die "ERROR: $pkg_version not found using pkg-config$pkg_config_fail_message"
}

hostcc_e(){
    eval printf '%s\\n' $HOSTCC_E
}

hostcc_o(){
    eval printf '%s\\n' $HOSTCC_O
}

check_host_cc(){
    log check_host_cc "$@"
    cat > $TMPC
    log_file $TMPC
    check_cmd $host_cc $host_cflags "$@" $HOSTCC_C $(hostcc_o $TMPO) $TMPC
}

check_host_cpp(){
    log check_host_cpp "$@"
    cat > $TMPC
    log_file $TMPC
    check_cmd $host_cc $host_cppflags $host_cflags "$@" $(hostcc_e $TMPO) $TMPC
}

check_host_cppflags(){
    log check_host_cppflags "$@"
    check_host_cpp "$@" <<EOF && append host_cppflags "$@"
#include <stdlib.h>
EOF
}

check_host_cflags(){
    log check_host_cflags "$@"
    set -- $($host_cflags_filter "$@")
    check_host_cc "$@" <<EOF && append host_cflags "$@"
int x;
EOF
}

check_host_cpp_condition(){
    log check_host_cpp_condition "$@"
    header=$1
    condition=$2
    shift 2
    check_host_cpp "$@" <<EOF
#include <$header>
#if !($condition)
#error "unsatisfied condition: $condition"
#endif
EOF
}

cp_if_changed(){
    cmp -s "$1" "$2" && { test "$quiet" != "yes" && echo "$2 is unchanged"; } && return
    mkdir -p "$(dirname $2)"
    cp -f "$1" "$2"
}

# CONFIG_LIST contains configurable options, while HAVE_LIST is for
# system-dependent things.

AVCODEC_COMPONENTS="
    bsfs
    decoders
    encoders
    hwaccels
    parsers
"

AVDEVICE_COMPONENTS="
    indevs
    outdevs
"

AVFILTER_COMPONENTS="
    filters
"

AVFORMAT_COMPONENTS="
    demuxers
    muxers
    protocols
"

COMPONENT_LIST="
    $AVCODEC_COMPONENTS
    $AVDEVICE_COMPONENTS
    $AVFILTER_COMPONENTS
    $AVFORMAT_COMPONENTS
"

EXAMPLE_LIST="
    avio_dir_cmd_example
    avio_reading_example
    decode_audio_example
    decode_video_example
    demuxing_decoding_example
    encode_audio_example
    encode_video_example
    extract_mvs_example
    filter_audio_example
    filtering_audio_example
    filtering_video_example
    http_multiclient_example
    hw_decode_example
    metadata_example
    muxing_example
    qsvdec_example
    remuxing_example
    resampling_audio_example
    scaling_video_example
    transcode_aac_example
    transcoding_example
    vaapi_encode_example
"

EXTERNAL_AUTODETECT_LIBRARY_LIST="
    alsa
    appkit
    avfoundation
    bzlib
    coreimage
    iconv
    libxcb
    libxcb_shm
    libxcb_shape
    libxcb_xfixes
    lzma
    schannel
    sdl2
    securetransport
    sndio
    xlib
    zlib
"

EXTERNAL_LIBRARY_GPL_LIST="
    avisynth
    frei0r
    libcdio
    librubberband
    libvidstab
    libx264
    libx265
    libxavs
    libxvid
"

EXTERNAL_LIBRARY_NONFREE_LIST="
    decklink
    libndi_newtek
    libfdk_aac
    openssl
    libtls
"

EXTERNAL_LIBRARY_VERSION3_LIST="
    gmp
    libopencore_amrnb
    libopencore_amrwb
    libvmaf
    libvo_amrwbenc
    rkmpp
"

EXTERNAL_LIBRARY_GPLV3_LIST="
    libsmbclient
"

EXTERNAL_LIBRARY_LIST="
    $EXTERNAL_LIBRARY_GPL_LIST
    $EXTERNAL_LIBRARY_NONFREE_LIST
    $EXTERNAL_LIBRARY_VERSION3_LIST
    $EXTERNAL_LIBRARY_GPLV3_LIST
    chromaprint
    gcrypt
    gnutls
    jni
    ladspa
    libass
    libbluray
    libbs2b
    libcaca
    libcelt
    libdc1394
    libdrm
    libflite
    libfontconfig
    libfreetype
    libfribidi
    libgme
    libgsm
    libiec61883
    libilbc
    libjack
    libkvazaar
    libmodplug
    libmp3lame
    libmysofa
    libopencv
    libopenh264
    libopenjpeg
    libopenmpt
    libopus
    libpulse
    librsvg
    librtmp
    libshine
    libsmbclient
    libsnappy
    libsoxr
    libspeex
    libssh
    libtesseract
    libtheora
    libtwolame
    libv4l2
    libvorbis
    libvpx
    libwavpack
    libwebp
    libxml2
    libzimg
    libzmq
    libzvbi
    lv2
    mediacodec
    openal
    opengl
"

HWACCEL_AUTODETECT_LIBRARY_LIST="
    amf
    audiotoolbox
    crystalhd
    cuda
    cuvid
    d3d11va
    dxva2
    nvdec
    nvenc
    vaapi
    vdpau
    videotoolbox
    v4l2_m2m
    xvmc
"

# catchall list of things that require external libs to link
EXTRALIBS_LIST="
    cpu_init
    cws2fws
"

HWACCEL_LIBRARY_NONFREE_LIST="
    cuda_sdk
    libnpp
"

HWACCEL_LIBRARY_LIST="
    $HWACCEL_LIBRARY_NONFREE_LIST
    libmfx
    mmal
    omx
    opencl
"

DOCUMENT_LIST="
    doc
    htmlpages
    manpages
    podpages
    txtpages
"

FEATURE_LIST="
    ftrapv
    gray
    hardcoded_tables
    omx_rpi
    runtime_cpudetect
    safe_bitstream_reader
    shared
    small
    static
    swscale_alpha
"

LIBRARY_LIST="
    avcodec
    avdevice
    avfilter
    avformat
    avresample
    avutil
    postproc
    swresample
    swscale
"

LICENSE_LIST="
    gpl
    nonfree
    version3
"

PROGRAM_LIST="
    ffplay
    ffprobe
    ffmpeg
"

SUBSYSTEM_LIST="
    dct
    dwt
    error_resilience
    faan
    fast_unaligned
    fft
    lsp
    lzo
    mdct
    pixelutils
    network
    rdft
"

# COMPONENT_LIST needs to come last to ensure correct dependency checking
CONFIG_LIST="
    $DOCUMENT_LIST
    $EXAMPLE_LIST
    $EXTERNAL_LIBRARY_LIST
    $EXTERNAL_AUTODETECT_LIBRARY_LIST
    $HWACCEL_LIBRARY_LIST
    $HWACCEL_AUTODETECT_LIBRARY_LIST
    $FEATURE_LIST
    $LICENSE_LIST
    $LIBRARY_LIST
    $PROGRAM_LIST
    $SUBSYSTEM_LIST
    autodetect
    fontconfig
    linux_perf
    memory_poisoning
    neon_clobber_test
    ossfuzz
    pic
    thumb
    valgrind_backtrace
    xmm_clobber_test
    $COMPONENT_LIST
"

THREADS_LIST="
    pthreads
    os2threads
    w32threads
"

ATOMICS_LIST="
    atomics_gcc
    atomics_suncc
    atomics_win32
"

AUTODETECT_LIBS="
    $EXTERNAL_AUTODETECT_LIBRARY_LIST
    $HWACCEL_AUTODETECT_LIBRARY_LIST
    $THREADS_LIST
"

ARCH_LIST="
    aarch64
    alpha
    arm
    avr32
    avr32_ap
    avr32_uc
    bfin
    ia64
    m68k
    mips
    mips64
    parisc
    ppc
    ppc64
    s390
    sh4
    sparc
    sparc64
    tilegx
    tilepro
    tomi
    x86
    x86_32
    x86_64
"

ARCH_EXT_LIST_ARM="
    armv5te
    armv6
    armv6t2
    armv8
    neon
    vfp
    vfpv3
    setend
"

ARCH_EXT_LIST_MIPS="
    mipsfpu
    mips32r2
    mips32r5
    mips64r2
    mips32r6
    mips64r6
    mipsdsp
    mipsdspr2
    msa
"

ARCH_EXT_LIST_LOONGSON="
    loongson2
    loongson3
    mmi
"

ARCH_EXT_LIST_X86_SIMD="
    aesni
    amd3dnow
    amd3dnowext
    avx
    avx2
    avx512
    fma3
    fma4
    mmx
    mmxext
    sse
    sse2
    sse3
    sse4
    sse42
    ssse3
    xop
"

ARCH_EXT_LIST_PPC="
    altivec
    dcbzl
    ldbrx
    power8
    ppc4xx
    vsx
"

ARCH_EXT_LIST_X86="
    $ARCH_EXT_LIST_X86_SIMD
    cpunop
    i686
"

ARCH_EXT_LIST="
    $ARCH_EXT_LIST_ARM
    $ARCH_EXT_LIST_PPC
    $ARCH_EXT_LIST_X86
    $ARCH_EXT_LIST_MIPS
    $ARCH_EXT_LIST_LOONGSON
"

ARCH_FEATURES="
    aligned_stack
    fast_64bit
    fast_clz
    fast_cmov
    local_aligned
    simd_align_16
    simd_align_32
    simd_align_64
"

BUILTIN_LIST="
    atomic_cas_ptr
    machine_rw_barrier
    MemoryBarrier
    mm_empty
    rdtsc
    sem_timedwait
    sync_val_compare_and_swap
"
HAVE_LIST_CMDLINE="
    inline_asm
    symver
    x86asm
"

HAVE_LIST_PUB="
    bigendian
    fast_unaligned
"

HEADERS_LIST="
    arpa_inet_h
    asm_types_h
    cdio_paranoia_h
    cdio_paranoia_paranoia_h
    cuda_h
    dispatch_dispatch_h
    dev_bktr_ioctl_bt848_h
    dev_bktr_ioctl_meteor_h
    dev_ic_bt8xx_h
    dev_video_bktr_ioctl_bt848_h
    dev_video_meteor_ioctl_meteor_h
    direct_h
    dirent_h
    dxgidebug_h
    dxva_h
    ES2_gl_h
    gsm_h
    io_h
    machine_ioctl_bt848_h
    machine_ioctl_meteor_h
    malloc_h
    opencv2_core_core_c_h
    OpenGL_gl3_h
    poll_h
    sys_param_h
    sys_resource_h
    sys_select_h
    sys_soundcard_h
    sys_time_h
    sys_un_h
    sys_videoio_h
    termios_h
    udplite_h
    unistd_h
    valgrind_valgrind_h
    windows_h
    winsock2_h
"

INTRINSICS_LIST="
    intrinsics_neon
"

COMPLEX_FUNCS="
    cabs
    cexp
"

MATH_FUNCS="
    atanf
    atan2f
    cbrt
    cbrtf
    copysign
    cosf
    erf
    exp2
    exp2f
    expf
    hypot
    isfinite
    isinf
    isnan
    ldexpf
    llrint
    llrintf
    log2
    log2f
    log10f
    lrint
    lrintf
    powf
    rint
    round
    roundf
    sinf
    trunc
    truncf
"

SYSTEM_FEATURES="
    dos_paths
    libc_msvcrt
    MMAL_PARAMETER_VIDEO_MAX_NUM_CALLBACKS