使用外部库构建 Xcode 项目时出现链接器错误
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Linker Error when building Xcode project using external library
提问by Ned W.
I am attempting to build a very simple command line application, in Xcode, that will print out basic information about MXF video files. In order to do this I need to use the libmxf, libbmx, and libbmx libraries available for download here:
我正在尝试在 Xcode 中构建一个非常简单的命令行应用程序，它将打印出有关 MXF 视频文件的基本信息。为此，我需要使用可在此处下载的 libmxf、libbmx 和 libbmx 库：
http://sourceforge.net/p/bmxlib/home/Home/
http://sourceforge.net/p/bmxlib/home/Home/
My C++ code is incredibly simple at this point:
在这一点上，我的 C++ 代码非常简单：
#include <iostream>
#include <cstdio>
#include <cstring>
#include <cerrno>
#include <vector>
#include <bmx/mxf_reader/MXFFileReader.h>
#include <bmx/mxf_reader/MXFGroupReader.h>
#include <bmx/mxf_reader/MXFSequenceReader.h>
#include <bmx/mxf_reader/MXFFrameMetadata.h>
#include <bmx/MXFUtils.h>
#include <bmx/Utils.h>
using namespace std;
using namespace bmx;
#define MXF_OPEN_READ(fn, pf) mxf_disk_file_open_read(fn, pf)
int main(int argc, const char * argv[])
{
std::vector<const char *> filenames;
std::cout << "mxfheader: execution beginning...\n";
for (int cmdln_index = 0; cmdln_index < argc; cmdln_index++) {
if (!check_file_exists(argv[cmdln_index])) {
if (argv[cmdln_index][0] == '-') {
fprintf(stderr, "Unknown argument '%s'\n", argv[cmdln_index]);
} else {
fprintf(stderr, "Failed to open input filename '%s'\n", argv[cmdln_index]);
}
return 1;
}
filenames.push_back(argv[cmdln_index]);
}
std::cout << filenames[0] << "\n";
return 0;
}
When I compiled the BMX library, I was sure to run configure with 64-bit support, like so:
当我编译 BMX 库时，我肯定会在 64 位支持下运行 configure，如下所示：
./configure --build=x86_64-apple-darwin11.4.2 --host=x86_64-apple-darwin11.4.2 CFLAGS="-arch x86_64" CXXFLAGS="-arch x86_64" LDFLAGS="-arch x86_64" CC=clang CXX=clang++
In the XCode Project under Build Settings, I have added /usr/local/lib to my Search Paths. Under Build Phases, I have added "libbmx-0.1.3.dylib", "libMXF-1.0.4.dylib", and "libMXF++-1.0.4.dylib" to the "Link Binary With Libraries" section.
在构建设置下的 XCode 项目中，我已将 /usr/local/lib 添加到我的搜索路径。在 Build Phases 下，我已将“libbmx-0.1.3.dylib”、“libMXF-1.0.4.dylib”和“libMXF++-1.0.4.dylib”添加到“Link Binary With Libraries”部分。
I have verified that these libraries are, indeed, 64-bit ( file libbmx-0.1.3.dylib returns libbmx-0.1.3.dylib: Mach-O 64-bit dynamically linked shared library x86_64 ).
我已经验证这些库确实是 64 位的（文件 libbmx-0.1.3.dylib 返回 libbmx-0.1.3.dylib: Mach-O 64 位动态链接共享库 x86_64 ）。
Every time I try and build the application, I get the following linker error:
每次我尝试构建应用程序时，都会收到以下链接器错误：
Ld /Users/ned/Library/Developer/Xcode/DerivedData/mxfheader-bkwawmplsoqpdadfxartceqkbolo/Build/Products/Debug/mxfheader normal x86_64
cd /Users/ned/Documents/src/mxfheader
setenv MACOSX_DEPLOYMENT_TARGET 10.7
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang++ -arch x86_64 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk -L/Users/ned/Library/Developer/Xcode/DerivedData/mxfheader-bkwawmplsoqpdadfxartceqkbolo/Build/Products/Debug -L/usr/local/lib -F/Users/ned/Library/Developer/Xcode/DerivedData/mxfheader-bkwawmplsoqpdadfxartceqkbolo/Build/Products/Debug -filelist /Users/ned/Library/Developer/Xcode/DerivedData/mxfheader-bkwawmplsoqpdadfxartceqkbolo/Build/Intermediates/mxfheader.build/Debug/mxfheader.build/Objects-normal/x86_64/mxfheader.LinkFileList -mmacosx-version-min=10.7 -stdlib=libc++ -lbmx-0.1.3 -lMXF-1.0.4 -lMXF++-1.0.4 -o /Users/ned/Library/Developer/Xcode/DerivedData/mxfheader-bkwawmplsoqpdadfxartceqkbolo/Build/Products/Debug/mxfheader
Undefined symbols for architecture x86_64:
"bmx::check_file_exists(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >)", referenced from:
_main in main.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
Any help would be appreciated. Thanks!
任何帮助，将不胜感激。谢谢！
回答by Petesh
Your problem is the option: -stdlib=libc++in the command line. It's causing a link to the wrong libc++, you need to make it -stdlib=libstdc++, as this is the stdlib that the libbmxlibrary is compiled against.
您的问题是选项：-stdlib=libc++在命令行中。它导致链接到错误的 libc++，您需要创建它-stdlib=libstdc++，因为这libbmx是编译库所针对的 stdlib 。
under the Apple LLVM compileroptions for the C++ standard library, select: libstdc++, or pick compiler default(which should choose libstdc++ also)
在Apple LLVM compilerC++ 标准库的选项下，选择:libstdc++或选择compiler default（也应该选择 libstdc++）
