ffmpeg/libavutil/internal.h

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/*
* copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
*
* This file is part of Libav.
*
* Libav 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.
*
* Libav 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 Libav; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/**
* @file
* common internal API header
*/
#ifndef AVUTIL_INTERNAL_H
#define AVUTIL_INTERNAL_H
#if !defined(DEBUG) && !defined(NDEBUG)
# define NDEBUG
#endif
#include <limits.h>
#include <stdint.h>
#include <stddef.h>
#include <assert.h>
#include "config.h"
#include "attributes.h"
#include "timer.h"
#include "dict.h"
#ifndef attribute_align_arg
#if ARCH_X86_32 && AV_GCC_VERSION_AT_LEAST(4,2)
# define attribute_align_arg __attribute__((force_align_arg_pointer))
#else
# define attribute_align_arg
#endif
#endif
Add support for building shared libraries with MSVC This requires the makedef perl script by Derek, from the c89-to-c99 repo. That scripts produces a .def file, listing the symbols to be exported, based on the gcc version scripts and the built object files. To properly load non-function symbols from DLL files, the data symbol declarations need to have the attribute __declspec(dllimport) when building the calling code. (On mingw, the linker can fix this up automatically, which is why it has not been an issue so far. If this attribute is omitted, linking actually succeeds, but reads from the table will not produce the desired results at runtime.) MSVC seems to manage to link DLLs (and run properly) even if this attribute is present while building the library itself (which normally isn't recommended) - other object files in the same library manage to link to the symbol (with a small warning at link time, like "warning LNK4049: locally defined symbol _avpriv_mpa_bitrate_tab imported" - it doesn't seem to be possible to squelch this warning), and the definition of the tables themselves produce a warning that can be squelched ("warning C4273: 'avpriv_mpa_bitrate_tab' : inconsistent dll linkage, see previous definition of 'avpriv_mpa_bitrate_tab'). In this setup, mingw isn't able to link object files that refer to data symbols with __declspec(dllimport) without those symbols actually being linked via a DLL (linking avcodec.dll ends up with errors like "undefined reference to `__imp__avpriv_mpa_freq_tab'"). The dllimport declspec isn't needed at all in mingw, so we simply choose not to declare it for other compilers than MSVC that requires it. (If ICL support later requires it, the condition can be extended later to include both of them.) This also implies that code that is built to link to a certain library as a DLL can't link to the same library as a static library. Therefore, we only allow building either static or shared but not both at the same time. (That is, static libraries as such can be, and actually are, built - this is used for linking the test tools to internal symbols in the libraries - but e.g. libavformat built to link to libavcodec as a DLL cannot link statically to libavcodec.) Also, linking to DLLs is slightly different from linking to shared libraries on other platforms. DLLs use a thing called import libraries, which is basically a stub library allowing the linker to know which symbols exist in the DLL and what name the DLL will have at runtime. In mingw/gcc, the import library is usually named libfoo.dll.a, which goes next to a static library named libfoo.a. This allows gcc to pick the dynamic one, if available, from the normal -lfoo switches, just as it does for libfoo.a vs libfoo.so on Unix. On MSVC however, you need to literally specify the name of the import library instead of the static library. Signed-off-by: Martin Storsjö <martin@martin.st>
2012-10-18 08:53:19 +00:00
#if defined(_MSC_VER) && CONFIG_SHARED
# define av_export __declspec(dllimport)
#else
# define av_export
#endif
#ifndef INT_BIT
# define INT_BIT (CHAR_BIT * sizeof(int))
#endif
#define FF_ALLOC_OR_GOTO(ctx, p, size, label)\
{\
p = av_malloc(size);\
if (p == NULL && (size) != 0) {\
av_log(ctx, AV_LOG_ERROR, "Cannot allocate memory.\n");\
goto label;\
}\
}
#define FF_ALLOCZ_OR_GOTO(ctx, p, size, label)\
{\
p = av_mallocz(size);\
if (p == NULL && (size) != 0) {\
av_log(ctx, AV_LOG_ERROR, "Cannot allocate memory.\n");\
goto label;\
}\
}
#include "libm.h"
/**
* Return NULL if CONFIG_SMALL is true, otherwise the argument
* without modification. Used to disable the definition of strings
* (for example AVCodec long_names).
*/
#if CONFIG_SMALL
# define NULL_IF_CONFIG_SMALL(x) NULL
#else
# define NULL_IF_CONFIG_SMALL(x) x
#endif
/**
* Define a function with only the non-default version specified.
*
* On systems with ELF shared libraries, all symbols exported from
* Libav libraries are tagged with the name and major version of the
* library to which they belong. If a function is moved from one
* library to another, a wrapper must be retained in the original
* location to preserve binary compatibility.
*
* Functions defined with this macro will never be used to resolve
* symbols by the build-time linker.
*
* @param type return type of function
* @param name name of function
* @param args argument list of function
* @param ver version tag to assign function
*/
#if HAVE_SYMVER_ASM_LABEL
# define FF_SYMVER(type, name, args, ver) \
type ff_##name args __asm__ (EXTERN_PREFIX #name "@" ver); \
type ff_##name args
#elif HAVE_SYMVER_GNU_ASM
# define FF_SYMVER(type, name, args, ver) \
__asm__ (".symver ff_" #name "," EXTERN_PREFIX #name "@" ver); \
type ff_##name args; \
type ff_##name args
#endif
/**
* Return NULL if a threading library has not been enabled.
* Used to disable threading functions in AVCodec definitions
* when not needed.
*/
#if HAVE_THREADS
# define ONLY_IF_THREADS_ENABLED(x) x
#else
# define ONLY_IF_THREADS_ENABLED(x) NULL
#endif
#if HAVE_MMX_INLINE
/**
* Empty mmx state.
* this must be called between any dsp function and float/double code.
* for example sin(); dsp->idct_put(); emms_c(); cos()
*/
static av_always_inline void emms_c(void)
{
__asm__ volatile ("emms" ::: "memory");
}
#elif HAVE_MMX && HAVE_MM_EMPTY
# include <mmintrin.h>
# define emms_c _mm_empty
#else
# define emms_c()
#endif /* HAVE_MMX_INLINE */
#endif /* AVUTIL_INTERNAL_H */