Libav链接错误：未定义的引用 [英] Libav linking error: undefined references

问题描述

这是我的问题：

• 我从源码（版本1.2）构建了ffmpeg，libav *库位于/ usr / local / lib，它们是静态的


• 我正在编译一个ns3（www.nsnam.org）模块，所以我对链接器的唯一控制是通过env变量LINKFLAGS


• 在源文件中，头文件是一个extern C块，所以它不是通常的g ++名称变化。


• 我设置LINKFLAGS = - 我/ usr / local / include / libavformat -I / usr / local / include / libavcodec -I / usr / local / include / libavutil -L / usr / local / lib -lavformat -lavcodec -lavutil，链接器似乎找不到任何的libav *函数（我得到很多未定义的引用，然后collect2：error：ld returned status 1

• I built ffmpeg from source (version 1.2), the libav* libraries are in /usr/local/lib and they're static
• I'm compiling a ns3 (www.nsnam.org) module, so my only control over the linker is through the env variable LINKFLAGS
• In the source the headers are in a "extern C" block, so it's not the usual g++ name mangling
• I set LINKFLAGS="-I/usr/local/include/libavformat -I/usr/local/include/libavcodec -I/usr/local/include/libavutil -L/usr/local/lib -lavformat -lavcodec -lavutil", and the linker can't seem to find any of the libav* functions I call (I get a lot of "undefined reference" and then "collect2: error: ld returned status 1"

任何人都可以帮我吗？谢谢...

Can anyone help me? Thanks...

编辑：这里有一些未定义的参考信息：

edit: here are a few of the undefined reference messages:

    ./libns3.14.1-qoe-monitor-debug.so: undefined reference to `av_guess_format'
    ./libns3.14.1-qoe-monitor-debug.so: undefined reference to `av_read_frame'
    ./libns3.14.1-qoe-monitor-debug.so: undefined reference to `avformat_write_header'
    ./libns3.14.1-qoe-monitor-debug.so: undefined reference to `av_interleaved_write_frame'
    ./libns3.14.1-qoe-monitor-debug.so: undefined reference to `av_find_stream_info'
    ./libns3.14.1-qoe-monitor-debug.so: undefined reference to `av_register_all'
    ./libns3.14.1-qoe-monitor-debug.so: undefined reference to `av_init_packet'
    ./libns3.14.1-qoe-monitor-debug.so: undefined reference to `avformat_alloc_context'
    ./libns3.14.1-qoe-monitor-debug.so: undefined reference to `av_dump_format'
    ./libns3.14.1-qoe-monitor-debug.so: undefined reference to `avio_close'

edit2：这里是build failed ：

edit2: here is the message I get after "build failed":

-> task in 'scratch-simulator' failed (exit status 1): 
{task 53952272: cxxprogram scratch-simulator.cc.1.o -> scratch-simulator}
['/usr/bin/g++', '-I/usr/local/include/libavcodec', '-I/usr/local/include/libavformat/',
 '-I/usr/local/include/libavutil/', '-L/usr/local/lib', '-I/usr/local
/include/libavcodec', '-I/usr/local/include/libavformat/', '-I/usr/local/include
/libavutil/', '-L/usr/local/lib', '-pthread', '-pthread', '-Wl,-z,relro', 
'scratch/scratch-simulator.cc.1.o', '-o', '/home/fede/Thesis/ns-allinone-3.14.1
/ns-3.14.1/build/scratch/scratch-simulator', '-Wl,-Bstatic', '-Wl,-Bdynamic', 
'-Wl,--no-as-needed', '-L.', '-L.', '-L.', '-L.', '-L.', '-L.', '-L.', '-L.', '-L.',
 '-L.', '-L.', '-L.', '-L.', '-L.', '-L.', '-L.', '-L.', '-L.', '-L.', '-L.', '-L.',
 '-L.', '-L.', '-L.', '-L.', '-L.', '-L.', '-L.', '-L.', '-L.', '-L.', '-L.', '-L.', 
'-L.', '-L.', '-L.', '-L.', '-L.', '-L/usr/lib', '-lns3.14.1-test-debug', '-lns3.14.1-
csma-layout-debug', '-lns3.14.1-point-to-point-layout-debug', '-lns3.14.1-netanim-
debug', '-lns3.14.1-lte-debug', '-lns3.14.1-spectrum-debug', '-lns3.14.1-antenna-
debug', '-lns3.14.1-aodv-debug', '-lns3.14.1-dsdv-debug', '-lns3.14.1-dsr-debug', 
'-lns3.14.1-mesh-debug', '-lns3.14.1-olsr-debug', '-lns3.14.1-csma-debug', '-lns3.14.1-
wimax-debug', '-lns3.14.1-applications-debug', '-lns3.14.1-virtual-net-device-debug', 
'-lns3.14.1-uan-debug', '-lns3.14.1-energy-debug', '-lns3.14.1-flow-monitor-debug', 
'-lns3.14.1-nix-vector-routing-debug', '-lns3.14.1-tap-bridge-debug', '-lns3.14.1-
visualizer-debug', '-lns3.14.1-internet-debug', '-lns3.14.1-bridge-debug', '-lns3.14.1-
point-to-point-debug', '-lns3.14.1-mpi-debug', '-lns3.14.1-wifi-debug', '-lns3.14.1-
buildings-debug', '-lns3.14.1-propagation-debug', '-lns3.14.1-mobility-debug', 
'-lns3.14.1-config-store-debug', '-lns3.14.1-tools-debug', '-lns3.14.1-stats-debug',
 '-lns3.14.1-emu-debug', '-lns3.14.1-topology-read-debug', '-lns3.14.1-network-debug', 
'-lns3.14.1-qoe-monitor-debug', '-lns3.14.1-core-debug', '-lrt', '-lgsl', 
'-lgslcblas', '-lm', '-ldl', '-lgtk-x11-2.0', '-lgdk-x11-2.0', '-latk-1.0', 
'-lgio-2.0', '-lpangoft2-1.0', '-lpangocairo-1.0', '-lgdk_pixbuf-2.0', '-lcairo', 
'-lpango-1.0', '-lfreetype', '-lfontconfig', '-lgobject-2.0', '-lglib-2.0', '-lxml2', 
'-lpython2.7']

推荐答案

库是C.库头不包含externC编译为C + +。在您的C ++源代码中执行此操作：

The libraries are C. The library headers don't include an extern "C" when compiled as C++. Do this in your C++ source:

extern "C" { 
#include <libavcodec/avcodec.h> 
#include <libavformat/avformat.h>
}

或者更一般地说，对于混合C和C ++源代码：

Or, more generically, for mixed C and C++ source:

#ifdef __cplusplus
extern "C" {
#endif
#include <libavcodec/avcodec.h> 
#include <libavformat/avformat.h>
#ifdef __cplusplus 
}
#endif

你应该不错。

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