[FFmpeg-devel] [PATCH] Shared library support for MSVC build.

[Ronald S. Bultje]

Hi,

On Tue, Oct 2, 2012 at 8:59 PM, jamal <jamrial at gmail.com> wrote:
> On 02/10/12 9:48 PM, Ronald S. Bultje wrote:
>> From: "Ronald S. Bultje" <rsbultje at gmail.com>
>>
>
>> diff --git a/libavcodec/ac3tab.h b/libavcodec/ac3tab.h
>> index d6e0eed..0063c8d 100644
>> --- a/libavcodec/ac3tab.h
>> +++ b/libavcodec/ac3tab.h
>> @@ -24,6 +24,7 @@
>>
>>  #include "libavutil/common.h"
>>  #include "ac3.h"
>> +#include "symbols.h"
>>
>>  #if CONFIG_HARDCODED_TABLES
>>  #   define HCONST const
>
>> diff --git a/libavcodec/symbols.h b/libavcodec/symbols.h
>> new file mode 100644
>> index 0000000..ca4a89d
>> --- /dev/null
>> +++ b/libavcodec/symbols.h
>> @@ -0,0 +1,32 @@
>> +/*
>> + * Copyright (c) 2012 Ronald S. Bultje <rsbultje at gmail.com>
>> + *
>> + * This file is part of FFmpeg.
>> + *
>> + * FFmpeg is free software; you can redistribute it and/or
>> + * modify it under the terms of the GNU Lesser General Public
>> + * License as published by the Free Software Foundation; either
>> + * version 2.1 of the License, or (at your option) any later version.
>> + *
>> + * FFmpeg is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>> + * Lesser General Public License for more details.
>> + *
>> + * You should have received a copy of the GNU Lesser General Public
>> + * License along with FFmpeg; if not, write to the Free Software
>> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
>> + */
>> +
>> +#ifndef AVCODEC_SYMBOLS_H
>> +#define AVCODEC_SYMBOLS_H
>> +
>> +#include "libavutil/avconfig.h"
>> +
>> +#if AV_HAVE_SHARED_LIBS && defined(_MSC_VER) && !defined(COMPILING_avcodec)
>> +#define AVCODEC_SYMBOL __declspec(dllimport)
>> +#else
>> +#define AVCODEC_SYMBOL
>> +#endif
>> +
>> +#endif /* AVCODEC_SYMBOLS_H */
>
>> diff --git a/libavutil/sha.h b/libavutil/sha.h
>> index d891cae..62e4edf 100644
>> --- a/libavutil/sha.h
>> +++ b/libavutil/sha.h
>> @@ -23,13 +23,15 @@
>>
>>  #include <stdint.h>
>>
>> +#include "symbols.h"
>> +
>>  /**
>>   * @defgroup lavu_sha SHA
>>   * @ingroup lavu_crypto
>
>>
>> diff --git a/libavutil/symbols.h b/libavutil/symbols.h
>> new file mode 100644
>> index 0000000..6011da2
>> --- /dev/null
>> +++ b/libavutil/symbols.h
>> @@ -0,0 +1,32 @@
>> +/*
>> + * Copyright (c) 2012 Ronald S. Bultje <rsbultje at gmail.com>
>> + *
>> + * This file is part of FFmpeg.
>> + *
>> + * FFmpeg is free software; you can redistribute it and/or
>> + * modify it under the terms of the GNU Lesser General Public
>> + * License as published by the Free Software Foundation; either
>> + * version 2.1 of the License, or (at your option) any later version.
>> + *
>> + * FFmpeg is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>> + * Lesser General Public License for more details.
>> + *
>> + * You should have received a copy of the GNU Lesser General Public
>> + * License along with FFmpeg; if not, write to the Free Software
>> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
>> + */
>> +
>> +#ifndef AVUTIL_SYMBOLS_H
>> +#define AVUTIL_SYMBOLS_H
>> +
>> +#include "libavutil/avconfig.h"
>> +
>> +#if AV_HAVE_SHARED_LIBS && defined(_MSC_VER) && !defined(COMPILING_avutil)
>> +#define AVUTIL_SYMBOL __declspec(dllimport)
>> +#else
>> +#define AVUTIL_SYMBOL
>> +#endif
>> +
>> +#endif /* AVUTIL_SYMBOLS_H */
>
> You're doing what you mentioned you wanted to avoid the other day: Create a header for essentially a single purpose/platform and include it in those files that would require it.
> __declspec() is an attribute, so you could instead add it to libavutil/attributes.h to more or less avoid that, since it's a widely used header.

Can do, but then I'd need to create a libavcodec/attributes.h also,
which I thought was kind of weird, i.e. you'd have
libavutil/attributes.h with all general attributes, and then
libavcodec/attributes.h with the symbol-stuff specific to libavcodec.
But sure if you prefer, I can do that too...

Ronald