[FFmpeg-devel] [PATCH 2/2] configure: libbsd support for arc4random()

[Ganesh Ajjanagadde]

On Mon, Dec 7, 2015 at 2:57 AM, Hendrik Leppkes <h.leppkes at gmail.com> wrote:
> On Mon, Dec 7, 2015 at 4:56 AM, Ganesh Ajjanagadde
> <gajjanagadde at gmail.com> wrote:
>> On non-BSD machines, there exists a package libbsd for providing BSD
>> functionality. This can be used to get support for arc4random.
>>
>> Thus, an opt-in --enable-libbsd is added to configure for this
>> functionality.
>>
>> Tested on GNU/Linux.
>>
>> Signed-off-by: Ganesh Ajjanagadde <gajjanagadde at gmail.com>
>> ---
>>  configure               | 23 +++++++++++++++++++++++
>>  libavutil/random_seed.c |  7 ++++++-
>>  2 files changed, 29 insertions(+), 1 deletion(-)
>>
>> diff --git a/configure b/configure
>> index e676269..bf18198 100755
>> --- a/configure
>> +++ b/configure
>> @@ -211,6 +211,7 @@ External library support:
>>    --enable-libass          enable libass subtitles rendering,
>>                             needed for subtitles and ass filter [no]
>>    --enable-libbluray       enable BluRay reading using libbluray [no]
>> +  --enable-libbsd          enable random seeding via arc4random [no]
>>    --enable-libbs2b         enable bs2b DSP library [no]
>>    --enable-libcaca         enable textual display using libcaca [no]
>>    --enable-libcelt         enable CELT decoding via libcelt [no]
>> @@ -1295,6 +1296,26 @@ require_pkg_config(){
>>      use_pkg_config "$@" || die "ERROR: $pkg not found using pkg-config$pkg_config_fail_message"
>>  }
>>
>> +require_libbsd(){
>> +    log require_libbsd "$@"
>> +    pkg="libbsd"
>> +    check_cmd $pkg_config --exists --print-errors $pkg \
>> +      || die "ERROR: $pkg not found"
>> +    pkg_cflags=$($pkg_config --cflags $pkg_config_flags $pkg)
>> +    pkg_libs=$($pkg_config --libs $pkg_config_flags $pkg)
>> +    {
>> +        echo "#define _DEFAULT_SOURCE"
>> +        echo "#include <bsd/stdlib.h>"
>> +        echo "long check_func(void) { return (long) arc4random; }"
>> +        echo "int main(void) { return 0; }"
>> +    } | check_ld "cc" $pkg_cflags $pkg_libs \
>> +      && set_safe "${pkg}_cflags" $pkg_cflags \
>> +      && set_safe "${pkg}_libs"   $pkg_libs \
>> +      || die "ERROR: $pkg not found"
>> +    add_cflags    $(get_safe "${pkg}_cflags")
>> +    add_extralibs $(get_safe "${pkg}_libs")
>> +}
>> +
>
> We don't usually define such functions for a dep, it would be better
> if you can implement the check using the normal "require" function, or
> even better if libbsd provides a pkgconfig file, use that.
> Or is there any particular reason why this would need a much more
> complex handling than default pkg config could offer?

This was the most annoying thing for me, and I could not get the
default pkgconfig file on Arch Linux to work. There seems to be only
one reason for it, so I would love to see ideas: it is to define
-D_DEFAULT_SOURCE or equivalently #define _DEFAULT_SOURCE while
testing for it. And the only reason for that is BSD's silly insistence
on non-portable, non-POSIX u_char data type.

>
>>  require_libfreetype(){
>>      log require_libfreetype "$@"
>>      pkg="freetype2"
>> @@ -1441,6 +1462,7 @@ EXTERNAL_LIBRARY_LIST="
>>      libaacplus
>>      libass
>>      libbluray
>> +    libbsd
>>      libbs2b
>>      libcaca
>>      libcdio
>> @@ -5386,6 +5408,7 @@ enabled libiec61883       && require libiec61883 libiec61883/iec61883.h iec61883
>>  enabled libaacplus        && require "libaacplus >= 2.0.0" aacplus.h aacplusEncOpen -laacplus
>>  enabled libass            && require_pkg_config libass ass/ass.h ass_library_init
>>  enabled libbluray         && require_pkg_config libbluray libbluray/bluray.h bd_open
>> +enabled libbsd            && require_libbsd
>>  enabled libbs2b           && require_pkg_config libbs2b bs2b.h bs2b_open
>>  enabled libcelt           && require libcelt celt/celt.h celt_decode -lcelt0 &&
>>                               { check_lib celt/celt.h celt_decoder_create_custom -lcelt0 ||
>> diff --git a/libavutil/random_seed.c b/libavutil/random_seed.c
>> index 205a636..464b406 100644
>> --- a/libavutil/random_seed.c
>> +++ b/libavutil/random_seed.c
>> @@ -20,6 +20,8 @@
>>
>>  #include "config.h"
>>
>> +#define _DEFAULT_SOURCE
>> +#define _BSD_SOURCE
>>  #if HAVE_UNISTD_H
>>  #include <unistd.h>
>>  #endif
>> @@ -30,6 +32,9 @@
>>  #include <windows.h>
>>  #include <wincrypt.h>
>>  #endif
>> +#if CONFIG_LIBBSD
>> +#include <bsd/stdlib.h>
>> +#endif
>>  #include <fcntl.h>
>>  #include <math.h>
>>  #include <time.h>
>> @@ -121,7 +126,7 @@ uint32_t av_get_random_seed(void)
>>      }
>>  #endif
>>
>> -#if HAVE_ARC4RANDOM
>> +#if HAVE_ARC4RANDOM || CONFIG_LIBBSD
>>      return arc4random();
>>  #endif
>>
>> --
>> 2.6.3
>>
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>> ffmpeg-devel at ffmpeg.org
>> http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
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