configure

        SLIB_INSTALL_EXTRA_SHLIB='$(SLIBNAME:$(SLIBSUF)=.lib)'
        SLIB_INSTALL_EXTRA_LIB='$(SLIBNAME_WITH_MAJOR:$(SLIBSUF)=.def)'
        SHFLAGS='-dll -def:$$(@:$(SLIBSUF)=.def) -implib:$(SUBDIR)$(SLIBNAME:$(SLIBSUF)=.lib)'
        objformat="win32"
        ranlib=:
        enable dos_paths
        ;;
    cygwin*)
        target_os=cygwin
        shlibdir_default="$bindir_default"
        SLIBPREF="cyg"
        SLIBSUF=".dll"
        SLIBNAME_WITH_VERSION='$(SLIBPREF)$(NAME)-$(LIBVERSION)$(SLIBSUF)'
        SLIBNAME_WITH_MAJOR='$(SLIBPREF)$(NAME)-$(LIBMAJOR)$(SLIBSUF)'
        SLIB_INSTALL_NAME='$(SLIBNAME_WITH_MAJOR)'
        SLIB_INSTALL_LINKS=
        SLIB_INSTALL_EXTRA_LIB='lib$(NAME).dll.a'
        SHFLAGS='-shared -Wl,--out-implib,$(SUBDIR)lib$(NAME).dll.a'
        objformat="win32"
        enable dos_paths
        ;;
    *-dos|freedos|opendos)
        network_extralibs="-lsocket"
        objformat="coff"
        enable dos_paths
        add_cppflags -U__STRICT_ANSI__
        ;;
    linux)
        enable dv1394
        enable section_data_rel_ro
        ;;
    irix*)
        target_os=irix
        ranlib="echo ignoring ranlib"
        ;;
    os/2*)
        ln_s="cp -f"
        objformat="aout"
        add_cppflags -D_GNU_SOURCE
        add_ldflags -Zomf -Zbin-files -Zargs-wild -Zhigh-mem -Zmap
        SHFLAGS='$(SUBDIR)$(NAME).def -Zdll -Zomf'
        LIBSUF="_s.a"
        SLIBPREF=""
        SLIBSUF=".dll"
        SLIBNAME_WITH_VERSION='$(SLIBPREF)$(NAME)-$(LIBVERSION)$(SLIBSUF)'
        SLIBNAME_WITH_MAJOR='$(SLIBPREF)$(shell echo $(NAME) | cut -c1-6)$(LIBMAJOR)$(SLIBSUF)'
        SLIB_CREATE_DEF_CMD='echo LIBRARY $(SLIBNAME_WITH_MAJOR) INITINSTANCE TERMINSTANCE > $(SUBDIR)$(NAME).def; \
            echo CODE PRELOAD MOVEABLE DISCARDABLE >> $(SUBDIR)$(NAME).def; \
            echo DATA PRELOAD MOVEABLE MULTIPLE NONSHARED >> $(SUBDIR)$(NAME).def; \
            echo EXPORTS >> $(SUBDIR)$(NAME).def; \
            emxexp $(OBJS) >> $(SUBDIR)$(NAME).def'
        SLIB_EXTRA_CMD='emximp -o $(SUBDIR)$(LIBPREF)$(NAME)_dll.a $(SUBDIR)$(NAME).def; \
            emximp -o $(SUBDIR)$(LIBPREF)$(NAME)_dll.lib $(SUBDIR)$(NAME).def;'
        SLIB_INSTALL_EXTRA_LIB='$(LIBPREF)$(NAME)_dll.a $(LIBPREF)$(NAME)_dll.lib'
        enable dos_paths
        ;;
    gnu/kfreebsd)
        add_cppflags -D_BSD_SOURCE
        ;;
    gnu)
        ;;
    qnx)
        add_cppflags -D_QNX_SOURCE
        network_extralibs="-lsocket"
        ;;
    symbian)
        SLIBSUF=".dll"
        enable dos_paths
        add_cflags --include=$sysinclude/gcce/gcce.h -fvisibility=default
        add_cppflags -D__GCCE__ -D__SYMBIAN32__ -DSYMBIAN_OE_POSIX_SIGNALS
        add_ldflags -Wl,--target1-abs,--no-undefined \
                    -Wl,-Ttext,0x80000,-Tdata,0x1000000 -shared \
                    -Wl,--entry=_E32Startup -Wl,-u,_E32Startup
        add_extralibs -l:eexe.lib -l:usrt2_2.lib -l:dfpaeabi.dso \
                      -l:drtaeabi.dso -l:scppnwdl.dso -lsupc++ -lgcc \
                      -l:libc.dso -l:libm.dso -l:euser.dso -l:libcrt0.lib
        ;;
    osf1)
        add_cppflags -D_OSF_SOURCE -D_POSIX_PII -D_REENTRANT
        ;;
    minix)
        ;;
    none)
        ;;
    *)
        die "Unknown OS '$target_os'."
        ;;
esac

# determine libc flavour

probe_libc(){
    pfx=$1
    pfx_no_=${pfx%_}
    # uclibc defines __GLIBC__, so it needs to be checked before glibc.
    if check_${pfx}cpp_condition features.h "defined __UCLIBC__"; then
        eval ${pfx}libc_type=uclibc
        add_${pfx}cppflags -D_POSIX_C_SOURCE=200112 -D_XOPEN_SOURCE=600
    elif check_${pfx}cpp_condition features.h "defined __GLIBC__"; then
        eval ${pfx}libc_type=glibc
        add_${pfx}cppflags -D_POSIX_C_SOURCE=200112 -D_XOPEN_SOURCE=600
    # MinGW headers can be installed on Cygwin, so check for newlib first.
    elif check_${pfx}cpp_condition newlib.h "defined _NEWLIB_VERSION"; then
        eval ${pfx}libc_type=newlib
        add_${pfx}cppflags -U__STRICT_ANSI__ -D_XOPEN_SOURCE=600
    # MinGW64 is backwards compatible with MinGW32, so check for it first.
    elif check_${pfx}cpp_condition _mingw.h "defined __MINGW64_VERSION_MAJOR"; then
        eval ${pfx}libc_type=mingw64
        add_${pfx}cppflags -U__STRICT_ANSI__ -D__USE_MINGW_ANSI_STDIO=1
        eval test \$${pfx_no_}cc_type = "gcc" &&
            add_${pfx}cppflags -D__printf__=__gnu_printf__
    elif check_${pfx}cpp_condition _mingw.h "defined __MINGW_VERSION"  ||
         check_${pfx}cpp_condition _mingw.h "defined __MINGW32_VERSION"; then
        eval ${pfx}libc_type=mingw32
        check_${pfx}cpp_condition _mingw.h "__MINGW32_MAJOR_VERSION > 3 || \
            (__MINGW32_MAJOR_VERSION == 3 && __MINGW32_MINOR_VERSION >= 15)" ||
            die "ERROR: MinGW32 runtime version must be >= 3.15."
        add_${pfx}cppflags -U__STRICT_ANSI__ -D__USE_MINGW_ANSI_STDIO=1
        check_${pfx}cpp_condition _mingw.h "__MSVCRT_VERSION__ < 0x0700__" &&
            add_${pfx}cppflags -D__MSVCRT_VERSION__=0x0700
        eval test \$${pfx_no_}cc_type = "gcc" &&
            add_${pfx}cppflags -D__printf__=__gnu_printf__
    elif check_${pfx}cpp_condition crtversion.h "defined _VC_CRT_MAJOR_VERSION"; then
        eval ${pfx}libc_type=msvcrt
        if check_${pfx}cpp_condition crtversion.h "_VC_CRT_MAJOR_VERSION < 14"; then
            if [ "$pfx" = host_ ]; then
                add_host_cppflags -Dsnprintf=_snprintf
            else
                add_compat strtod.o strtod=avpriv_strtod
                add_compat msvcrt/snprintf.o snprintf=avpriv_snprintf   \
                                             _snprintf=avpriv_snprintf  \
                                             vsnprintf=avpriv_vsnprintf
            fi
        fi
        add_${pfx}cppflags -D_USE_MATH_DEFINES -D_CRT_SECURE_NO_WARNINGS -D_CRT_NONSTDC_NO_WARNINGS
        # The MSVC 2010 headers (Win 7.0 SDK) set _WIN32_WINNT to
        # 0x601 by default unless something else is set by the user.
        # This can easily lead to us detecting functions only present
        # in such new versions and producing binaries requiring windows 7.0.
        # Therefore explicitly set the default to XP unless the user has
        # set something else on the command line.
        # Don't do this if WINAPI_FAMILY is set and is set to a non-desktop
        # family. For these cases, configure is free to use any functions
        # found in the SDK headers by default. (Alternatively, we could force
        # _WIN32_WINNT to 0x0602 in that case.)
        check_${pfx}cpp_condition stdlib.h "defined(_WIN32_WINNT)" ||
            { check_${pfx}cpp <<EOF && add_${pfx}cppflags -D_WIN32_WINNT=0x0502; }
#ifdef WINAPI_FAMILY
#include <winapifamily.h>
#if !WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP)
#error not desktop
#endif
#endif
EOF
        if [ "$pfx" = "" ]; then
            check_func strtoll || add_cflags -Dstrtoll=_strtoi64
        fi
    elif check_${pfx}cpp_condition stddef.h "defined __KLIBC__"; then
        eval ${pfx}libc_type=klibc
    elif check_${pfx}cpp_condition sys/cdefs.h "defined __BIONIC__"; then
        eval ${pfx}libc_type=bionic
    elif check_${pfx}cpp_condition sys/brand.h "defined LABELED_BRAND_NAME"; then
        eval ${pfx}libc_type=solaris
        add_${pfx}cppflags -D__EXTENSIONS__ -D_XOPEN_SOURCE=600
    else
        eval ${pfx}libc_type=default
        add_${pfx}cppflags -D_DEFAULT_SOURCE
    fi
}

probe_libc
test -n "$libc_type" && enable libc_$libc_type
probe_libc host_
test -n "$host_libc_type" && enable host_libc_$host_libc_type

# hacks for compiler/libc/os combinations

case $libc_type in
    bionic)
        add_compat strtod.o strtod=avpriv_strtod
        ;;
    glibc)
        if enabled tms470; then
            CPPFLAGS="-I${source_path}/compat/tms470 ${CPPFLAGS}"
            add_cppflags -D__USER_LABEL_PREFIX__=
            add_cppflags -D__builtin_memset=memset
            add_cppflags -D__gnuc_va_list=va_list -D_VA_LIST_DEFINED
            add_cflags   -pds=48    # incompatible redefinition of macro
        elif enabled ccc; then
            add_ldflags -Wl,-z,now  # calls to libots crash without this
        fi
        ;;
esac

check_compile_assert flt_lim "float.h limits.h" "DBL_MAX == (double)DBL_MAX" ||
    add_cppflags '-I\$(SRC_PATH)/compat/float'

esc(){
    echo "$*" | sed 's/%/%25/g;s/:/%3a/g'
}

echo "config:$arch:$subarch:$cpu:$target_os:$(esc $cc_ident):$(esc $LIBAV_CONFIGURATION)" > avbuild/config.fate

check_cpp_condition stdlib.h "defined(__PIC__) || defined(__pic__) || defined(PIC)" && enable_weak pic

set_default $PATHS_LIST
set_default nm

# we need to build at least one lib type
if ! enabled_any static shared; then
    cat <<EOF
At least one library type must be built.
Specify --enable-static to build the static libraries or --enable-shared to
build the shared libraries as well. To only build the shared libraries specify
--disable-static in addition to --enable-shared.
EOF
    exit 1
fi

disabled optimizations || check_cflags -fomit-frame-pointer

enable_weak_pic() {
    disabled pic && return
    enable pic
    add_cppflags -DPIC
    case "$target_os" in
    mingw*|cygwin*)
        ;;
    *)
        add_cflags -fPIC
        ;;
    esac
    add_asflags  -fPIC
}

enabled pic && enable_weak_pic

check_cc <<EOF || die "Symbol mangling check failed."
int ff_extern;
EOF
sym=$($nm $TMPO | awk '/ff_extern/{ print substr($0, match($0, /[^ \t]*ff_extern/)) }')
extern_prefix=${sym%%ff_extern*}

check_inline_asm inline_asm '"" ::'

_restrict=
for restrict_keyword in restrict __restrict__ __restrict; do
    check_cc <<EOF && _restrict=$restrict_keyword && break
void foo(char * $restrict_keyword p);
EOF
done

check_cc <<EOF && enable pragma_deprecated
void foo(void) { _Pragma("GCC diagnostic ignored \"-Wdeprecated-declarations\"") }
EOF

check_cc <<EOF && enable attribute_packed
struct { int x; } __attribute__((packed)) x;
EOF

check_cc <<EOF && enable attribute_may_alias
union { int x; } __attribute__((may_alias)) x;
EOF

check_cc <<EOF || die "endian test failed"
unsigned int endian = 'B' << 24 | 'I' << 16 | 'G' << 8 | 'E';
EOF
od -t x1 $TMPO | grep -q '42 *49 *47 *45' && enable bigendian

check_gas() {
    log "check_gas using '$as' as AS"
    # :vararg is used on aarch64, arm and ppc altivec
    check_as <<EOF || return 1
.macro m n, y:vararg=0
\n: .int \y
.endm
m x
EOF
    # .altmacro is only used in arm asm
    ! enabled arm || check_as <<EOF || return 1
.altmacro
EOF
    enable gnu_as
    return 0
}

if enabled_any arm aarch64 || enabled_all ppc altivec && enabled asm; then
    nogas=:
    enabled_any arm aarch64 && nogas=die
    enabled_all ppc altivec && nogas=warn
    as_noop=-v

    case $as_type in
        arm*) gaspp_as_type=armasm; as_noop=-h ;;
        gcc)  gaspp_as_type=gas ;;
        *)    gaspp_as_type=$as_type ;;
    esac

    [ $target_os = "darwin" ] && gaspp_as_type="apple-$gaspp_as_type"

    check_cmd gas-preprocessor.pl -arch $arch -as-type $gaspp_as_type -- $as $as_noop &&
        gas="gas-preprocessor.pl -arch $arch -as-type $gaspp_as_type -- $as"

    if ! check_gas ; then
        as=${gas:=$as}
        check_gas || \
            $nogas "GNU assembler not found, install/update gas-preprocessor"
    fi

    check_as <<EOF && enable as_func
.func test
.endfunc
EOF
fi

check_inline_asm inline_asm_labels '"1:\n"'

if enabled aarch64; then
    enabled armv8 && check_insn armv8 'prfm   pldl1strm, [x0]'
    # internal assembler in clang 3.3 does not support this instruction
    enabled neon && check_insn neon 'ext   v0.8B, v0.8B, v1.8B, #1'
    enabled vfp  && check_insn vfp  'fmadd d0,    d0,    d1,    d2'

    map 'enabled_any ${v}_external ${v}_inline || disable $v' $ARCH_EXT_LIST_ARM

elif enabled alpha; then

    check_cflags -mieee

elif enabled arm; then

    enabled msvc && check_cpp_condition stddef.h "defined _M_ARMT" && enable thumb
    check_cpp_condition stddef.h "defined __thumb__" && enable_weak thumb
    enabled thumb && check_cflags -mthumb || check_cflags -marm

    if     check_cpp_condition stddef.h "defined __ARM_PCS_VFP"; then
        enable vfp_args
    elif check_cpp_condition stddef.h "defined _M_ARM_FP && _M_ARM_FP >= 30"; then
        enable vfp_args
    elif ! check_cpp_condition stddef.h "defined __ARM_PCS || defined __SOFTFP__" && [ $target_os != darwin ]; then
        case "${cross_prefix:-$cc}" in
            *hardfloat*)         enable vfp_args;   fpabi=vfp ;;
            *) check_ld <<EOF && enable vfp_args && fpabi=vfp || fpabi=soft ;;
__asm__ (".eabi_attribute 28, 1");
int main(void) { return 0; }
EOF
        esac
        warn "Compiler does not indicate floating-point ABI, guessing $fpabi."
    fi

    enabled armv5te && check_insn armv5te 'qadd r0, r0, r0'
    enabled armv6   && check_insn armv6   'sadd16 r0, r0, r0'
    enabled armv6t2 && check_insn armv6t2 'movt r0, #0'
    enabled neon    && check_insn neon    'vadd.i16 q0, q0, q0'
    enabled vfp     && check_insn vfp     'fadds s0, s0, s0'
    enabled vfpv3   && check_insn vfpv3   'vmov.f32 s0, #1.0'

    [ $target_os = linux ] || [ $target_os = android ] ||
        map 'enabled_any ${v}_external ${v}_inline || disable $v' \
            $ARCH_EXT_LIST_ARM

    check_inline_asm asm_mod_q '"add r0, %Q0, %R0" :: "r"((long long)0)'

    check_as <<EOF && enable as_dn_directive
ra .dn d0.i16
.unreq ra
EOF
    check_as <<EOF && enable as_fpu_directive
.fpu neon
EOF

    # llvm's integrated assembler supports .object_arch from llvm 3.5
    [ "$objformat" = elf ] && check_as <<EOF && enable as_object_arch
.object_arch armv4
EOF

    [ $target_os != win32 ] && enabled_all armv6t2 shared !pic && enable_weak_pic

elif enabled mips; then

    check_inline_asm loongson '"dmult.g $1, $2, $3"'

    # make sure that only an instruction set is enabled
    disable mips64r6 mips32r6 mips64r2 mips32r2 mips64r1 mips32r1

    if enabled mips64; then
        check_inline_asm mips64r6 '"dlsa $0, $0, $0, 1"' ||
            check_inline_asm mips64r2 '"dext $0, $0, 0, 1"' ||
                check_inline_asm mips64r1 '"daddi $0, $0, 0"'
    else
        check_inline_asm mips32r6 '"aui $0, $0, 0"' ||
            check_inline_asm mips32r2 '"ext $0, $0, 0, 1"' ||
                check_inline_asm mips32r1 '"addi $0, $0, 0"'
    fi

elif enabled parisc; then

    if enabled gcc; then
        case $($cc -dumpversion) in
            4.[3-8].*) check_cflags -fno-optimize-sibling-calls ;;
        esac
    fi

elif enabled ppc; then

    enable local_aligned_8 local_aligned_16 local_aligned_32

    check_inline_asm dcbzl     '"dcbzl 0, %0" :: "r"(0)'
    check_inline_asm ibm_asm   '"add 0, 0, 0"'
    check_inline_asm ppc4xx    '"maclhw r10, r11, r12"'
    check_inline_asm xform_asm '"lwzx %1, %y0" :: "Z"(*(int*)0), "r"(0)'

    # AltiVec flags: The FSF version of GCC differs from the Apple version
    if enabled altivec; then
        check_cflags -maltivec -mabi=altivec &&
        { check_header altivec.h && inc_altivec_h="#include <altivec.h>" ; } ||
        check_cflags -faltivec

        # check if our compiler supports Motorola AltiVec C API
        check_cc <<EOF || disable altivec
$inc_altivec_h
int main(void) {
    vector signed int v1 = (vector signed int) { 0 };
    vector signed int v2 = (vector signed int) { 1 };
    v1 = vec_add(v1, v2);
    return 0;
}
EOF

        enabled altivec || warn "Altivec disabled, possibly missing --cpu flag"
    fi

    if enabled vsx; then
        check_cflags -mvsx &&
        check_builtin vec_vsx_ld "altivec.h" "__builtin_vec_vsx_ld" || disable vsx
    fi

    if enabled power8; then
        check_cpp_condition "altivec.h" "defined(_ARCH_PWR8)" || disable power8
    fi

elif enabled x86; then

    check_builtin rdtsc    intrin.h   "__rdtsc()"
    check_builtin mm_empty mmintrin.h "_mm_empty()"

    enable local_aligned_8 local_aligned_16 local_aligned_32

    # check whether EBP is available on x86
    # As 'i' is stored on the stack, this program will crash
    # if the base pointer is used to access it because the
    # base pointer is cleared in the inline assembly code.
    check_exec_crash <<EOF && enable ebp_available
volatile int i=0;
__asm__ volatile ("xorl %%ebp, %%ebp" ::: "%ebp");
return i;
EOF

    # check whether EBX is available on x86
    check_inline_asm ebx_available '""::"b"(0)' &&
        check_inline_asm ebx_available '"":::"%ebx"'

    # check whether xmm clobbers are supported
    check_inline_asm xmm_clobbers '"":::"%xmm0"'

    # check whether binutils is new enough to compile SSSE3/MMXEXT
    enabled ssse3  && check_inline_asm ssse3_inline  '"pabsw %xmm0, %xmm0"'
    enabled mmxext && check_inline_asm mmxext_inline '"pmaxub %mm0, %mm1"'

    if ! disabled_any asm mmx yasm; then
        if check_cmd $yasmexe --version; then
            enabled x86_64 && yasm_extra="-m amd64"
            yasm_debug="-g dwarf2"
        elif check_cmd nasm -v; then
            yasmexe=nasm
            yasm_debug="-g -F dwarf"
            enabled x86_64 && test "$objformat" = elf && objformat=elf64
        fi

        YASMFLAGS="-f $objformat $yasm_extra"
        enabled pic               && append YASMFLAGS "-DPIC"
        test -n "$extern_prefix"  && append YASMFLAGS "-DPREFIX"
        case "$objformat" in
            elf*) enabled debug && append YASMFLAGS $yasm_debug ;;
        esac

        check_yasm "movbe ecx, [5]" && enable yasm ||
            die "yasm/nasm not found or too old. Use --disable-yasm for a crippled build."
        check_yasm "vextracti128 xmm0, ymm0, 0"      || disable avx2_external
        check_yasm "vpmacsdd xmm0, xmm1, xmm2, xmm3" || disable xop_external
        check_yasm "vfmadd132ps ymm0, ymm1, ymm2"    || disable fma3_external
        check_yasm "vfmaddps ymm0, ymm1, ymm2, ymm3" || disable fma4_external
        check_yasm "CPU amdnop" || disable cpunop
    fi

    case "$cpu" in
        athlon*|opteron*|k8*|pentium|pentium-mmx|prescott|nocona|atom|geode)
            disable fast_clz
        ;;
    esac

fi

check_code cc arm_neon.h "int16x8_t test = vdupq_n_s16(0)" && enable intrinsics_neon

check_ldflags -Wl,--as-needed

if ! disabled network; then
    check_func getaddrinfo $network_extralibs
    check_func inet_aton $network_extralibs

    check_type netdb.h "struct addrinfo"
    check_type netinet/in.h "struct group_source_req" -D_BSD_SOURCE
    check_type netinet/in.h "struct ip_mreq_source" -D_BSD_SOURCE
    check_type netinet/in.h "struct ipv6_mreq" -D_DARWIN_C_SOURCE
    check_type poll.h "struct pollfd"
    check_type netinet/sctp.h "struct sctp_event_subscribe"
    check_struct "sys/types.h sys/socket.h" "struct sockaddr" sa_len
    check_type netinet/in.h "struct sockaddr_in6"
    check_type "sys/types.h sys/socket.h" "struct sockaddr_storage"
    check_type "sys/types.h sys/socket.h" socklen_t

    # Prefer arpa/inet.h over winsock2
    if check_header arpa/inet.h ; then
        check_func closesocket
    elif check_header winsock2.h ; then
        check_func_headers winsock2.h closesocket -lws2 &&
            network_extralibs="-lws2" ||
        { check_func_headers winsock2.h closesocket -lws2_32 &&
            network_extralibs="-lws2_32"; } || disable winsock2_h network
        check_func_headers ws2tcpip.h getaddrinfo $network_extralibs

        check_type ws2tcpip.h socklen_t
        check_type ws2tcpip.h "struct addrinfo"
        check_type ws2tcpip.h "struct group_source_req"
        check_type ws2tcpip.h "struct ip_mreq_source"
        check_type ws2tcpip.h "struct ipv6_mreq"
        check_type winsock2.h "struct pollfd"
        check_struct winsock2.h "struct sockaddr" sa_len
        check_type ws2tcpip.h "struct sockaddr_in6"
        check_type ws2tcpip.h "struct sockaddr_storage"
    else
        disable network
    fi
fi

check_builtin atomic_cas_ptr atomic.h "void **ptr; void *oldval, *newval; atomic_cas_ptr(ptr, oldval, newval)"
check_builtin machine_rw_barrier mbarrier.h "__machine_rw_barrier()"
check_builtin MemoryBarrier windows.h "MemoryBarrier()"
check_builtin sync_val_compare_and_swap "" "int *ptr; int oldval, newval; __sync_val_compare_and_swap(ptr, oldval, newval)"

case "$custom_allocator" in
    jemalloc)
        # jemalloc by default does not use a prefix
        require libjemalloc jemalloc/jemalloc.h malloc -ljemalloc
    ;;
    tcmalloc)
        require_pkg_config libtcmalloc libtcmalloc gperftools/tcmalloc.h tc_malloc
        malloc_prefix=tc_
    ;;
esac

check_func_headers malloc.h _aligned_malloc     && enable aligned_malloc
check_func  ${malloc_prefix}memalign            && enable memalign
check_func  ${malloc_prefix}posix_memalign      && enable posix_memalign

check_cpp_condition unistd.h "defined(_POSIX_MONOTONIC_CLOCK)" &&
    check_func_headers time.h clock_gettime ||
        check_lib clock_gettime time.h clock_gettime -lrt

check_func  fcntl
check_func  fork
check_func  gethrtime
check_func  getopt
check_func  getrusage
check_func  gettimeofday
check_func  gmtime_r
check_func  isatty
check_func  localtime_r
check_func  mach_absolute_time
check_func  mkstemp
check_func  mmap
check_func  mprotect
# Solaris has nanosleep in -lrt, OpenSolaris no longer needs that
check_func_headers time.h nanosleep || check_lib nanosleep time.h nanosleep -lrt
check_func  sched_getaffinity
check_func  setrlimit
check_func  strerror_r
check_func  sysconf
check_func  sysctl
check_func  usleep

check_func_headers io.h setmode
check_func_headers stdlib.h getenv

check_func_headers windows.h GetProcessAffinityMask
check_func_headers windows.h GetProcessTimes
check_func_headers windows.h GetSystemTimeAsFileTime
check_func_headers windows.h LoadLibrary
check_func_headers windows.h MapViewOfFile
check_func_headers windows.h SetConsoleTextAttribute
check_func_headers windows.h Sleep
check_func_headers windows.h VirtualAlloc
check_struct windows.h "CONDITION_VARIABLE" Ptr

check_header d3d11.h
check_header direct.h
check_header dlfcn.h
check_header dxva.h
check_header dxva2api.h
check_header io.h
check_header mach/mach_time.h
check_header malloc.h
check_header poll.h
check_header sys/mman.h
check_header sys/param.h
check_header sys/resource.h
check_header sys/select.h
check_header sys/time.h
check_header sys/un.h
check_header unistd.h
check_header valgrind/valgrind.h
check_header VideoDecodeAcceleration/VDADecoder.h
check_header windows.h
check_header X11/extensions/XvMClib.h

# it seems there are versions of clang in some distros that try to use the
# gcc headers, which explodes for stdatomic
# so we also check that atomics actually work here
check_builtin stdatomic_h stdatomic.h "atomic_int foo; atomic_store(&foo, 0)"

check_lib shell32  "windows.h shellapi.h" CommandLineToArgvW   -lshell32
check_lib wincrypt "windows.h wincrypt.h" CryptGenRandom       -ladvapi32
check_lib psapi    "windows.h psapi.h"    GetProcessMemoryInfo -lpsapi

check_struct "sys/time.h sys/resource.h" "struct rusage" ru_maxrss

check_type "windows.h dxva.h" "DXVA_PicParams_HEVC" -DWINAPI_FAMILY=WINAPI_FAMILY_DESKTOP_APP -D_CRT_BUILD_DESKTOP_APP=0
check_type "windows.h d3d11.h" "ID3D11VideoDecoder"
check_type "d3d9.h dxva2api.h" DXVA2_ConfigPictureDecode -D_WIN32_WINNT=0x0602

check_type "va/va.h va/va_dec_hevc.h" "VAPictureParameterBufferHEVC"
check_type "va/va.h va/va_dec_vp8.h" "VAPictureParameterBufferVP8"
check_type "va/va.h va/va_vpp.h" "VAProcPipelineParameterBuffer"
check_type "va/va.h va/va_enc_h264.h" "VAEncPictureParameterBufferH264"
check_type "va/va.h va/va_enc_hevc.h" "VAEncPictureParameterBufferHEVC"
check_type "va/va.h va/va_enc_jpeg.h" "VAEncPictureParameterBufferJPEG"
check_type "va/va.h va/va_enc_mpeg2.h" "VAEncPictureParameterBufferMPEG2"
check_type "va/va.h va/va_enc_vp8.h"  "VAEncPictureParameterBufferVP8"

check_type "vdpau/vdpau.h" "VdpPictureInfoHEVC"

if ! disabled w32threads && ! enabled pthreads; then
    check_lib w32threads "windows.h process.h" _beginthreadex
fi

# check for some common methods of building with pthread support
# do this before the optional library checks as some of them require pthreads
if ! disabled pthreads && ! enabled w32threads; then
    if check_lib pthreads pthread.h pthread_join -pthread; then
        add_cflags -pthread
    elif check_lib pthreads pthread.h pthread_join -pthreads; then
        add_cflags -pthreads
    elif check_lib pthreads pthread.h pthread_join -lpthreadGC2; then
        :
    elif check_lib pthreads pthread.h pthread_join -lpthread; then
        :
    elif check_func pthread_join; then
        enable pthreads
    fi
fi

enabled pthreads &&
    check_builtin sem_timedwait semaphore.h "sem_t *s; sem_init(s,0,0); sem_timedwait(s,0); sem_destroy(s)"

disabled  zlib || check_lib  zlib  zlib.h      zlibVersion -lz
disabled bzlib || check_lib bzlib bzlib.h BZ2_bzlibVersion -lbz2

# On some systems dynamic loading requires no extra linker flags
check_lib libdl dlfcn.h dlopen || check_lib libdl dlfcn.h dlopen -ldl

check_lib libm math.h sin -lm

atan2f_args=2
ldexpf_args=2
powf_args=2

for func in $MATH_FUNCS; do
    eval check_mathfunc $func \${${func}_args:-1} $libm_extralibs
done

# these are off by default, so fail if requested and not available
enabled avisynth          && require_header avisynth/avisynth_c.h
enabled avxsynth          && require_header avxsynth/avxsynth_c.h
enabled cuda              && require cuda cuda.h cuInit -lcuda
enabled frei0r            && require_header frei0r.h
enabled gnutls            && require_pkg_config gnutls gnutls gnutls/gnutls.h gnutls_global_init
enabled libbs2b           && require_pkg_config libbs2b libbs2b bs2b.h bs2b_open
enabled libdc1394         && require_pkg_config libdc1394 libdc1394-2 dc1394/dc1394.h dc1394_new
enabled libdcadec         && require libdcadec libdcadec/dca_context.h dcadec_context_create -ldcadec
enabled libfaac           && require libfaac "stdint.h faac.h" faacEncGetVersion -lfaac
enabled libfdk_aac        && require_pkg_config libfdk_aac fdk-aac "fdk-aac/aacenc_lib.h" aacEncOpen
enabled libfontconfig     && require_pkg_config libfontconfig fontconfig "fontconfig/fontconfig.h" FcInit
enabled libfreetype       && require_pkg_config libfreetype freetype2 "ft2build.h FT_FREETYPE_H" FT_Init_FreeType
enabled libgsm            && { for gsm_hdr in "gsm.h" "gsm/gsm.h"; do
                                   check_lib libgsm "${gsm_hdr}" gsm_create -lgsm && break;
                               done || die "ERROR: libgsm not found"; }
enabled libhdcd           && require_pkg_config libhdcd libhdcd "hdcd/hdcd_simple.h" hdcd_new
enabled libilbc           && require libilbc ilbc.h WebRtcIlbcfix_InitDecode -lilbc
enabled libkvazaar        && require_pkg_config libkvazaar "kvazaar >= 0.8.1" kvazaar.h kvz_api_get
enabled libmfx            && require_pkg_config libmfx libmfx "mfx/mfxvideo.h" MFXInit
enabled libmp3lame        && require "libmp3lame >= 3.98.3" lame/lame.h lame_set_VBR_quality -lmp3lame
enabled libnpp            && require libnpp npp.h nppGetLibVersion -lnppi -lnppc
enabled libopencore_amrnb && require libopencore_amrnb opencore-amrnb/interf_dec.h Decoder_Interface_init -lopencore-amrnb
enabled libopencore_amrwb && require libopencore_amrwb opencore-amrwb/dec_if.h D_IF_init -lopencore-amrwb
enabled libopencv         && require_pkg_config libopencv opencv opencv/cv.h cvCreateImageHeader
enabled libopenh264       && require_pkg_config libopenh264 openh264 wels/codec_api.h WelsGetCodecVersion
enabled libopenjpeg       && { check_lib libopenjpeg openjpeg.h opj_version -lopenjpeg -DOPJ_STATIC ||
                               require_pkg_config libopenjpeg libopenjpeg1 openjpeg.h opj_version -DOPJ_STATIC; }
enabled libopus           && require_pkg_config libopus opus opus_multistream.h opus_multistream_decoder_create
enabled libpulse          && require_pkg_config libpulse libpulse-simple pulse/simple.h pa_simple_new
enabled librtmp           && require_pkg_config librtmp librtmp librtmp/rtmp.h RTMP_Socket
enabled libschroedinger   && require_pkg_config libschroedinger schroedinger-1.0 schroedinger/schro.h schro_init
enabled libsnappy         && require libsnappy snappy-c.h snappy_compress -lsnappy
enabled libspeex          && require_pkg_config libspeex speex speex/speex.h speex_decoder_init -lspeex
enabled libtheora         && require libtheora theora/theoraenc.h th_info_init -ltheoraenc -ltheoradec -logg
enabled libtwolame        && require libtwolame twolame.h twolame_init -ltwolame
enabled libvo_aacenc      && require libvo_aacenc vo-aacenc/voAAC.h voGetAACEncAPI -lvo-aacenc
enabled libvo_amrwbenc    && require libvo_amrwbenc vo-amrwbenc/enc_if.h E_IF_init -lvo-amrwbenc
enabled libvorbis         && require libvorbis vorbis/vorbisenc.h vorbis_info_init -lvorbisenc -lvorbis -logg
enabled libvpx            && require_pkg_config libvpx "vpx >= 1.3.0" vpx/vpx_codec.h vpx_codec_version &&
                             { enabled libvpx_vp8_decoder &&
                                   check_pkg_config libvpx_vp8_decoder vpx "vpx/vpx_decoder.h vpx/vp8dx.h" vpx_codec_vp8_dx
                               enabled libvpx_vp8_encoder &&
                                   check_pkg_config libvpx_vp8_encoder vpx "vpx/vpx_encoder.h vpx/vp8cx.h" vpx_codec_vp8_cx
                               enabled libvpx_vp9_decoder &&
                                   check_pkg_config libvpx_vp9_decoder vpx "vpx/vpx_decoder.h vpx/vp8dx.h" vpx_codec_vp9_dx
                               enabled libvpx_vp9_encoder &&
                                   check_pkg_config libvpx_vp9_encoder vpx "vpx/vpx_encoder.h vpx/vp8cx.h" vpx_codec_vp9_cx
                               disabled_all libvpx_vp8_decoder libvpx_vp9_decoder libvpx_vp8_encoder libvpx_vp9_encoder &&
                                   die "libvpx enabled but no supported decoders/encoders found"
                             }
enabled libwavpack        && require libwavpack wavpack/wavpack.h WavpackOpenFileOutput  -lwavpack
enabled libwebp           && require_pkg_config libwebp libwebp webp/encode.h WebPGetEncoderVersion
enabled libx264           && require_pkg_config libx264 x264 "stdint.h x264.h" x264_encoder_encode &&
                             require_cpp_condition x264.h "X264_BUILD >= 118" &&
                             { check_cpp_condition x264.h "X264_MPEG2" &&
                               enable libx262; }
enabled libx265           && require_pkg_config libx265 x265 x265.h x265_api_get &&
                             require_cpp_condition x265.h "X265_BUILD >= 57"
enabled libxavs           && require libxavs "stdint.h xavs.h" xavs_encoder_encode -lxavs
enabled libxvid           && require libxvid xvid.h xvid_global -lxvidcore
enabled mmal              && { check_lib mmal interface/mmal/mmal.h mmal_port_connect -lmmal_core -lmmal_util -lmmal_vc_client -lbcm_host ||
                               { ! enabled cross_compile &&
                                 add_cflags -isystem/opt/vc/include/ -isystem/opt/vc/include/interface/vmcs_host/linux -isystem/opt/vc/include/interface/vcos/pthreads -fgnu89-inline &&
                                 add_ldflags -L/opt/vc/lib/ &&
                                 check_lib mmal interface/mmal/mmal.h mmal_port_connect -lmmal_core -lmmal_util -lmmal_vc_client -lbcm_host; } ||
                               die "ERROR: mmal not found" &&
                               check_func_headers interface/mmal/mmal.h "MMAL_PARAMETER_VIDEO_MAX_NUM_CALLBACKS"; }
enabled omx               && require_header OMX_Core.h
enabled omx_rpi           && { check_header OMX_Core.h ||
                               { ! enabled cross_compile && add_cflags -isystem/opt/vc/include/IL && check_header OMX_Core.h ; } ||
                               die "ERROR: OpenMAX IL headers not found"; } && enable omx
enabled openssl           && { { check_pkg_config openssl openssl openssl/ssl.h OPENSSL_init_ssl ||
                                 check_pkg_config openssl openssl openssl/ssl.h SSL_library_init; } ||
                               check_lib openssl openssl/ssl.h SSL_library_init -lssl -lcrypto ||
                               check_lib openssl openssl/ssl.h SSL_library_init -lssl32 -leay32 ||
                               check_lib openssl openssl/ssl.h SSL_library_init -lssl -lcrypto -lws2_32 -lgdi32 ||
                               die "ERROR: openssl not found"; }

enabled gnutls            && check_lib gmp gmp.h mpz_export -lgmp

if enabled nvenc; then
    require_header nvEncodeAPI.h
    require_cpp_condition nvEncodeAPI.h "NVENCAPI_MAJOR_VERSION >= 6"
fi

check_pkg_config sdl "sdl >= 1.2.1 sdl < 1.3.0" SDL_events.h SDL_PollEvent

! disabled pod2man   && check_cmd pod2man --help     && enable pod2man   || disable pod2man
! disabled texi2html && check_cmd texi2html -version && enable texi2html || disable texi2html

check_header linux/fb.h
check_header linux/videodev2.h
check_struct linux/videodev2.h "struct v4l2_frmivalenum" discrete

check_header AVFoundation/AVFoundation.h

check_header sys/videoio.h

check_lib user32 "windows.h winuser.h" GetShellWindow -luser32
check_lib vfw32 "windows.h vfw.h" capCreateCaptureWindow -lvfw32
# check that WM_CAP_DRIVER_CONNECT is defined to the proper value
# w32api 3.12 had it defined wrong
check_cpp_condition vfw.h "WM_CAP_DRIVER_CONNECT > WM_USER" && enable vfwcap_defines

# check for ioctl_meteor.h, ioctl_bt848.h and alternatives
{ check_header dev/bktr/ioctl_meteor.h &&
  check_header dev/bktr/ioctl_bt848.h; } ||
{ check_header machine/ioctl_meteor.h &&
  check_header machine/ioctl_bt848.h; } ||
{ check_header dev/video/meteor/ioctl_meteor.h &&
  check_header dev/video/bktr/ioctl_bt848.h; } ||
check_header dev/ic/bt8xx.h

check_header sys/soundcard.h
check_header soundcard.h

enabled_any alsa_indev alsa_outdev &&
    check_lib alsa alsa/asoundlib.h snd_pcm_htimestamp -lasound

enabled jack_indev && check_lib jack jack/jack.h jack_client_open -ljack &&
    check_func jack_port_get_latency_range -ljack

enabled_any sndio_indev sndio_outdev && check_lib sndio sndio.h sio_open -lsndio

if enabled libcdio; then
    check_lib libcdio "cdio/cdda.h cdio/paranoia.h" cdio_cddap_open -lcdio_paranoia -lcdio_cdda -lcdio ||
    check_lib libcdio "cdio/paranoia/cdda.h cdio/paranoia/paranoia.h" cdio_cddap_open -lcdio_paranoia -lcdio_cdda -lcdio ||
    die "ERROR: No usable libcdio/cdparanoia found"
fi

if enabled libxcb; then
    require_pkg_config libxcb xcb xcb/xcb.h xcb_connect
    require_pkg_config libxcb_shape xcb-shape xcb/shape.h xcb_shape_rectangles
    disabled libxcb_shm ||
        check_pkg_config libxcb_shm xcb-shm xcb/shm.h xcb_shm_attach
    disabled libxcb_xfixes ||
        check_pkg_config libxcb_xfixes xcb-xfixes xcb/xfixes.h xcb_xfixes_get_cursor_image
fi

enabled dxva2 &&
    check_lib dxva2_lib windows.h CoTaskMemFree -lole32

enabled vaapi && require vaapi va/va.h vaInitialize -lva

enabled vaapi &&
    check_code cc "va/va.h" "vaCreateSurfaces(0, 0, 0, 0, 0, 0, 0, 0)" ||
    disable vaapi

enabled vaapi &&
    check_lib vaapi_drm "va/va.h va/va_drm.h" vaGetDisplayDRM -lva -lva-drm

enabled vaapi &&
    check_lib vaapi_x11 "va/va.h va/va_x11.h" vaGetDisplay -lva -lva-x11 -lX11

enabled vdpau &&
    check_cpp_condition vdpau/vdpau.h "defined VDP_DECODER_PROFILE_MPEG4_PART2_ASP" ||
    disable vdpau

enabled vdpau &&
    check_lib vdpau_x11 "vdpau/vdpau.h vdpau/vdpau_x11.h" vdp_device_create_x11 -lvdpau -lX11

enabled debug && add_cflags -g"$debuglevel" && add_asflags -g"$debuglevel"

# add some useful compiler flags if supported
check_cflags -Wdeclaration-after-statement
check_cflags -Wall
check_cflags -Wdisabled-optimization
check_cflags -Wpointer-arith
check_cflags -Wredundant-decls
check_cflags -Wwrite-strings
check_cflags -Wtype-limits
check_cflags -Wundef
check_cflags -Wmissing-prototypes
check_cflags -Wstrict-prototypes

if enabled extra_warnings; then
    check_cflags -Wcast-qual
    check_cflags -Wextra
    check_cflags -Wpedantic
fi

check_disable_warning(){
    warning_flag=-W${1#-Wno-}
    test_cflags $warning_flag && add_cflags $1
}

check_disable_warning -Wno-parentheses
check_disable_warning -Wno-switch
check_disable_warning -Wno-format-zero-length
check_disable_warning -Wno-pointer-sign

check_disable_warning_headers(){
    warning_flag=-W${1#-Wno-}
    test_cflags $warning_flag && add_cflags_headers $1
}

check_disable_warning_headers -Wno-deprecated-declarations
check_disable_warning_headers -Wno-unused-variable

check_objcflags -fobjc-arc && enable objc_arc

check_cc <<EOF && enable blocks_extension
void (^block)(void);
EOF

# add some linker flags
check_ldflags -Wl,--warn-common
check_ldflags -Wl,-rpath-link=libswscale:libavfilter:libavdevice:libavformat:libavcodec:libavutil:libavresample
enabled rpath && add_ldexeflags -Wl,-rpath,$libdir
test_ldflags -Wl,-Bsymbolic && append SHFLAGS -Wl,-Bsymbolic

# add some strip flags
# -wN '..@*' is more selective than -x, but not available everywhere.
check_stripflags -wN \'..@*\' || check_stripflags -x || strip='true'

enabled neon_clobber_test &&
    check_ldflags -Wl,--wrap,avcodec_open2              \
                  -Wl,--wrap,avcodec_decode_audio4      \
                  -Wl,--wrap,avcodec_decode_video2      \
                  -Wl,--wrap,avcodec_decode_subtitle2   \
                  -Wl,--wrap,avcodec_encode_audio2      \
                  -Wl,--wrap,avcodec_encode_video2      \
                  -Wl,--wrap,avcodec_encode_subtitle    \
                  -Wl,--wrap,avcodec_send_packet        \
                  -Wl,--wrap,avcodec_receive_packet     \
                  -Wl,--wrap,avcodec_send_frame         \
                  -Wl,--wrap,avcodec_receive_frame      \
                  -Wl,--wrap,avresample_convert ||
    disable neon_clobber_test

enabled xmm_clobber_test &&
    check_ldflags -Wl,--wrap,avcodec_open2              \
                  -Wl,--wrap,avcodec_decode_audio4      \
                  -Wl,--wrap,avcodec_decode_video2      \
                  -Wl,--wrap,avcodec_decode_subtitle2   \
                  -Wl,--wrap,avcodec_encode_audio2      \
                  -Wl,--wrap,avcodec_encode_video2      \
                  -Wl,--wrap,avcodec_encode_subtitle    \
                  -Wl,--wrap,avcodec_send_packet        \
                  -Wl,--wrap,avcodec_receive_packet     \
                  -Wl,--wrap,avcodec_send_frame         \
                  -Wl,--wrap,avcodec_receive_frame      \
                  -Wl,--wrap,avresample_convert         \
                  -Wl,--wrap,sws_scale ||
    disable xmm_clobber_test

check_ld <<EOF && enable proper_dce
extern const int array[512];
static inline int func(void) { return array[0]; }
int main(void) { return 0; }
EOF

if enabled proper_dce; then
    echo "X { local: *; };" > $TMPV
    if test_ldflags -Wl,${version_script},$TMPV; then
        append SHFLAGS '-Wl,${version_script},\$(SUBDIR)lib\$(NAME).ver'
        check_cc <<EOF && enable symver_asm_label
void ff_foo(void) __asm__ ("av_foo@VERSION");
void ff_foo(void) { ${inline_asm+__asm__($quotes);} }
EOF
        check_cc <<EOF && enable symver_gnu_asm
__asm__(".symver ff_foo,av_foo@VERSION");
void ff_foo(void) {}
EOF
    fi
fi

if [ -z "$optflags" ]; then
    if enabled small; then
        optflags=$cflags_size
    elif enabled optimizations; then
        optflags=$cflags_speed
    else
        optflags=$cflags_noopt
    fi
fi

check_optflags(){
    check_cflags "$@"
    enabled lto && check_ldflags "$@"
}

check_optflags $optflags
check_optflags -fno-math-errno
check_optflags -fno-signed-zeros

if enabled lto; then
    test "$cc_type" != "$ld_type" && die "LTO requires same compiler and linker"
    check_cflags  -flto
    check_ldflags -flto $cpuflags
fi

if enabled icc; then
    # Just warnings, no remarks
    check_cflags -w1
    # -wd: Disable following warnings
    # 144, 167, 556: -Wno-pointer-sign
    # 1292: attribute "foo" ignored
    # 1419: external declaration in primary source file
    # 10006: ignoring unknown option -fno-signed-zeros
    # 10148: ignoring unknown option -Wno-parentheses
    # 10156: ignoring option '-W'; no argument required
    check_cflags -wd144,167,556,1292,1419,10006,10148,10156
    # 11030: Warning unknown option --as-needed
    # 10156: ignoring option '-export'; no argument required
    check_ldflags -wd10156,11030
    # icc 11.0 and 11.1 work with ebp_available, but don't pass the test
    enable ebp_available