如何在arm64 MacOS上链接libvlc.dylib和libvlccore.dylib来为VLC创建解码器模块？

Question

我正在尝试为VLC创建一个解码器模块，为了创建最终的共享库，我需要访问libvlc.dylib和libvlccore.dylib中定义的函数。但是，当我尝试将目标文件与 VLC 库链接时，我收到此错误：

Undefined symbols for architecture arm64:
  "_block_Release", referenced from:
      _Decode in my_decoder.o
ld: symbol(s) not found for architecture arm64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

这是我正在运行的链接命令：

g++ my_decoder.o -L/Applications/VLC.app/Contents/MacOS/lib -lvlc -lvlccore -dynamiclib -o libmy_decoder.dylib

这是 my_decoder.c 的内容：

#include <vlc_common.h>
#include <vlc_plugin.h>
#include <vlc_codec.h>

#define MODULE_STRING "My Decoder"

vlc_module_begin()
        /*
         * Module details
         * Set capability and function callbacks
         */
vlc_module_end()

static int Open(vlc_object_t *p_this) {

        /*
         * Create the decoder
         * Set pf_decode = Decode;
         */

        return VLCDEC_SUCCESS;

}

static int Decode(decoder_t *p_dec, block_t *p_block) {

        /*    
         * Decode the data in p_block, and create p_pic
         */

        // decoder_QueueVideo does not produce linking errors
        decoder_QueueVideo(p_dec, &p_pic);
        // block_Release cannot be identified by linker
        block_Release(p_block);

        return VLCDEC_SUCCESS;

}

static int Close(vlc_object_t *p_this) {

        /*
         * Close the decoder
         */

        return VLC_SUCCESS;

}

我使用以下命令编译 my_decoder.c：

gcc -std=gnu99 -I/path/to/vlc/header/files/ -g -Wall -fPIC my_decoder.c -c -o my_decoder.o

备注：

• 我下载了适用于 MacOS 通用二进制文件的 VLC 预编译版本
• VLC 版本 3.0.21
• 我能够在 Ubuntu 上毫无问题地完成所有这些步骤，这让我相信问题出在 MacOS 或 arm64/x86 架构差异上

Answer 1

如果您的两个

dylib

是通用的，则需要剥离 x86_64 部分：

lipo -remove x86_64 /path/to/fatlib.dylib -output /path/to/thinlib.dylib

• lipo -info

  会告诉你它是否胖，以及存在哪些架构：

% lipo /path/to/fatlib.dylib
Architectures in the fat file: /path/to/fatlib.dylib are: x86_64 arm64

• 您还可以使用

  file

  检查存在哪些架构：

% file /path/to/fatlib.dylib
/path/to/fatlib.dylib: Mach-O universal binary with 2 architectures: 
[x86_64:Mach-O 64-bit dynamically linked shared library x86_64
- Mach-O 64-bit dynamically linked shared library x86_64] [arm64]
/path/to/fatlib.dylib (for architecture x86_64):    Mach-O 64-bit 
dynamically linked shared library x86_64
/path/to/fatlib.dylib (for architecture arm64): Mach-O 64-bit 
dynamically linked shared library arm64