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d66c52c2b3
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>
183 lines
5.1 KiB
C
183 lines
5.1 KiB
C
/*
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* copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
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*
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* This file is part of Libav.
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*
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* Libav is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* Libav is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with Libav; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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/**
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* @file
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* common internal API header
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*/
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#ifndef AVUTIL_INTERNAL_H
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#define AVUTIL_INTERNAL_H
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#if !defined(DEBUG) && !defined(NDEBUG)
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# define NDEBUG
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#endif
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#include <limits.h>
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#include <stdint.h>
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#include <stddef.h>
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#include <assert.h>
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#include "config.h"
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#include "attributes.h"
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#include "timer.h"
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#include "dict.h"
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#ifndef attribute_align_arg
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#if ARCH_X86_32 && AV_GCC_VERSION_AT_LEAST(4,2)
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# define attribute_align_arg __attribute__((force_align_arg_pointer))
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#else
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# define attribute_align_arg
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#endif
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#endif
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#if defined(_MSC_VER) && CONFIG_SHARED
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# define av_export __declspec(dllimport)
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#else
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# define av_export
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#endif
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#ifndef INT_BIT
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# define INT_BIT (CHAR_BIT * sizeof(int))
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#endif
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/* avoid usage of dangerous/inappropriate system functions */
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#undef malloc
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#define malloc please_use_av_malloc
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#undef free
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#define free please_use_av_free
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#undef realloc
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#define realloc please_use_av_realloc
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#undef time
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#define time time_is_forbidden_due_to_security_issues
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#undef rand
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#define rand rand_is_forbidden_due_to_state_trashing_use_av_lfg_get
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#undef srand
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#define srand srand_is_forbidden_due_to_state_trashing_use_av_lfg_init
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#undef random
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#define random random_is_forbidden_due_to_state_trashing_use_av_lfg_get
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#undef sprintf
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#define sprintf sprintf_is_forbidden_due_to_security_issues_use_snprintf
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#undef strcat
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#define strcat strcat_is_forbidden_due_to_security_issues_use_av_strlcat
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#undef exit
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#define exit exit_is_forbidden
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#undef printf
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#define printf please_use_av_log_instead_of_printf
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#undef fprintf
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#define fprintf please_use_av_log_instead_of_fprintf
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#undef puts
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#define puts please_use_av_log_instead_of_puts
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#undef perror
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#define perror please_use_av_log_instead_of_perror
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#undef strcasecmp
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#define strcasecmp please_use_av_strcasecmp
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#undef strncasecmp
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#define strncasecmp please_use_av_strncasecmp
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#define FF_ALLOC_OR_GOTO(ctx, p, size, label)\
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{\
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p = av_malloc(size);\
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if (p == NULL && (size) != 0) {\
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av_log(ctx, AV_LOG_ERROR, "Cannot allocate memory.\n");\
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goto label;\
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}\
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}
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#define FF_ALLOCZ_OR_GOTO(ctx, p, size, label)\
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{\
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p = av_mallocz(size);\
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if (p == NULL && (size) != 0) {\
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av_log(ctx, AV_LOG_ERROR, "Cannot allocate memory.\n");\
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goto label;\
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}\
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}
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#include "libm.h"
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/**
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* Return NULL if CONFIG_SMALL is true, otherwise the argument
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* without modification. Used to disable the definition of strings
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* (for example AVCodec long_names).
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*/
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#if CONFIG_SMALL
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# define NULL_IF_CONFIG_SMALL(x) NULL
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#else
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# define NULL_IF_CONFIG_SMALL(x) x
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#endif
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/**
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* Define a function with only the non-default version specified.
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*
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* On systems with ELF shared libraries, all symbols exported from
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* Libav libraries are tagged with the name and major version of the
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* library to which they belong. If a function is moved from one
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* library to another, a wrapper must be retained in the original
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* location to preserve binary compatibility.
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*
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* Functions defined with this macro will never be used to resolve
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* symbols by the build-time linker.
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*
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* @param type return type of function
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* @param name name of function
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* @param args argument list of function
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* @param ver version tag to assign function
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*/
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#if HAVE_SYMVER_ASM_LABEL
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# define FF_SYMVER(type, name, args, ver) \
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type ff_##name args __asm__ (EXTERN_PREFIX #name "@" ver); \
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type ff_##name args
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#elif HAVE_SYMVER_GNU_ASM
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# define FF_SYMVER(type, name, args, ver) \
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__asm__ (".symver ff_" #name "," EXTERN_PREFIX #name "@" ver); \
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type ff_##name args; \
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type ff_##name args
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#endif
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/**
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* Return NULL if a threading library has not been enabled.
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* Used to disable threading functions in AVCodec definitions
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* when not needed.
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*/
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#if HAVE_THREADS
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# define ONLY_IF_THREADS_ENABLED(x) x
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#else
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# define ONLY_IF_THREADS_ENABLED(x) NULL
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#endif
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#if HAVE_MMX_INLINE
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/**
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* Empty mmx state.
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* this must be called between any dsp function and float/double code.
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* for example sin(); dsp->idct_put(); emms_c(); cos()
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*/
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static av_always_inline void emms_c(void)
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{
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__asm__ volatile ("emms" ::: "memory");
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}
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#elif HAVE_MMX && HAVE_MM_EMPTY
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# include <mmintrin.h>
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# define emms_c _mm_empty
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#else
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# define emms_c()
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#endif /* HAVE_MMX_INLINE */
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#endif /* AVUTIL_INTERNAL_H */
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