一尘不染

在cgo库中链接第三方静态库

go

我有一个Go库,它为C ++
OpenImageIO库(OpenImageiGO)提供绑定。我一直在通过与libOpenImageIO的标准动态链接来构建绑定,但现在尝试静态链接。我遇到了一个问题,无论我尝试使用哪种标志组合,外部链接器都会失败,并出现大量“未定义的引用”错误。我似乎回想起过去曾提到过的这个问题,他说链接器看到符号的顺序存在问题。但我似乎再也找不到此信息。

这是我最近一次构建尝试的简短示例,试图将其链接到boost,OpenColorIO和OpenImageIO的静态构建:

$ export CGO_CPPFLAGS="\
-I/path/to/boost/include \
-I/path/to/OpenColorIO/include \
-I/path/to/OpenImageIO/include"

$ export CGO_LDFLAGS="\
-L/path/to/boost/lib -lboost_thread_static -lboost_system_static \
-L/path/to/OpenColorIO/lib -lopencolorio \
-L/path/to/OpenImageIO/lib -lOpenImageIO"

$ go build -v -x --ldflags '-extldflags "-static"'  github.com/justinfx/openimageigo
...
CGO_LDFLAGS="/path/to/boost/lib/libboost_system_static.a" "/path/to/boost/lib/libboost_thread_static.a" "/path/to/OpenColorIO/lib/libopencolorio.a" "/path/to/OpenImageIO/lib/libOpenImageIO.a" "-lstdc++" /vol/apps/go/1.3.0/pkg/tool/linux_amd64/cgo -objdir $WORK/github.com/justinfx/openimageigo/_obj/ -- -I/path/to/boost/include -I/path/to/OpenColorIO/include -I/path/to/OpenImageIO/include -I./cpp -I $WORK/github.com/justinfx/openimageigo/_obj/ -I/path/to/boost/include -I/path/to/OpenColorIO/include -I/path/to/OpenImageIO/include color.go imagebuf.go imagebufalgo.go imagecache.go imageinput.go imageoutput.go imagespec.go oiio.go roi.go
...
/usr/bin/g++ -I . -fPIC -m64 -pthread -fmessage-length=0 -I/path/to/boost/include -I/path/to/OpenColorIO/include -I/path/to/OpenImageIO/include -I./cpp -I $WORK/github.com/justinfx/openimageigo/_obj/ -g -O2 -o $WORK/github.com/justinfx/openimageigo/_obj/all.cpp.o -c ./all.cpp

/usr/bin/g++ -I . -fPIC -m64 -pthread -fmessage-length=0 -o $WORK/github.com/justinfx/openimageigo/_obj/_cgo_.o $WORK/github.com/justinfx/openimageigo/_obj/_cgo_main.o $WORK/github.com/justinfx/openimageigo/_obj/_cgo_export.o $WORK/github.com/justinfx/openimageigo/_obj/color.cgo2.o $WORK/github.com/justinfx/openimageigo/_obj/imagebuf.cgo2.o $WORK/github.com/justinfx/openimageigo/_obj/imagebufalgo.cgo2.o $WORK/github.com/justinfx/openimageigo/_obj/imagecache.cgo2.o $WORK/github.com/justinfx/openimageigo/_obj/imageinput.cgo2.o $WORK/github.com/justinfx/openimageigo/_obj/imageoutput.cgo2.o $WORK/github.com/justinfx/openimageigo/_obj/imagespec.cgo2.o $WORK/github.com/justinfx/openimageigo/_obj/oiio.cgo2.o $WORK/github.com/justinfx/openimageigo/_obj/roi.cgo2.o $WORK/github.com/justinfx/openimageigo/_obj/all.cpp.o /path/to/boost/lib/libboost_system_static.a /path/to/boost/lib/libboost_thread_static.a /path/to/OpenColorIO/lib/libopencolorio.a /path/to/OpenImageIO/lib/libOpenImageIO.a -lstdc++

这是一些挑剔的错误,因为它的输出非常长:

/path/to/OpenImageIO/lib/libOpenImageIO.a(OpenImageIO_dist^src^libOpenImageIO^color_ocio.cpp.o): In function `ColorConfig':
/path/to/OpenImageIO/OpenImageIO_dist/src/libOpenImageIO/color_ocio.cpp:141: undefined reference to `OpenColorIO::v1::SetLoggingLevel(OpenColorIO::v1::LoggingLevel)'
...
/path/to/OpenImageIO/lib/libOpenImageIO.a(OpenImageIO_dist^src^libOpenImageIO^imagebufalgo_copy.cpp.o): In function `boost::shared_mutex::lock()':
/path/to/boost/include/boost/thread/pthread/shared_mutex.hpp:138: undefined reference to `boost::this_thread::disable_interruption::~disable_interruption()'

OpenImageIO似乎找不到OpenColorIO的引用。而且,OpenImageIO似乎找不到增强的参考。看起来在链接过程中发生的事情的顺序没有使OpenColorIO或boost符号可用于OpenImageIO,因此出现了很多符号错误。

我希望我正在做一些简单而愚蠢的事情,可以在构建过程中纠正它。但是,与默认的动态链接方法相比,使用外部库的cgo静态链接看起来确实更复杂。

更新#1

@ james-henstridge给出的答案是正确的,除了最后一个打ic之外,我几乎完全熟练。我收到了yaml- cpp所需的对的引用失败OpenColorIO,即使看起来顺序正确也是如此。

这是我最新的环境,在这里我处理了必须添加的所有显式静态库:

$ export CGO_CPPFLAGS="-I/usr/local/include -I/usr/include"

$ export CGO_LDFLAGS="\
-L/usr/local/lib \
-L/usr/lib \
-L/usr/lib/x86_64-linux-gnu \
-lOpenImageIO \
-lHalf -lIex -lfreetype -lIlmThread -lImath -lIlmImf -lIlmThread \
-lOpenColorIO \
-lyaml-cpp -ltinyxml \
-lboost_regex -lboost_filesystem -lboost_thread -lboost_system \
-ltiff -lgif -lpng -ljpeg -lz \
-lrt -ldl"

$ go test -v -x --ldflags '-extldflags "-static"' github.com/justinfx/openimageigo
...
/home/justin/src/OpenColorIO/src/core/OCIOYaml.cpp:329: undefined reference to `YAML::Node::begin() const'
...
/home/justin/src/OpenColorIO/build/ext/dist/include/yaml-cpp/nodereadimpl.h:79: undefined reference to `YAML::Node::GetScalar(std::basic_string<char, std::char_traits<char>, std::allocator<char> >&) const'
...
/usr/local/lib/libOpenColorIO.a(OCIOYaml.cpp.o): In function `_FindFromNodeAtIndex':
/home/justin/src/OpenColorIO/build/ext/dist/include/yaml-cpp/nodeutil.h:53: undefined reference to `YAML::Node::FindAtIndex(unsigned long) const'
collect2: ld returned 1 exit status

更新#2

没关系更新#1。它与特定问题有关,OpenColorIO而不是一般问题。


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2020-07-02

共1个答案

一尘不染

-l与静态库链接时,标志的顺序很重要。如果使用链接-lfoo -lbar -lbazlibbar.a则只会在libbar.a和中搜索所需的任何符号libbaz.a。即使libfoo.a包含您需要的符号,链接器也不会找到它们。

发生的情况是,对于每个库,链接器都会解压缩存档文件,并添加包含目标符号的目标文件,这些符号由之前的内容引用。如果不需要存档中的特定对象文件,则将其忽略。

解决方法是确保在链接器标志所依赖的库之前,先列出每个库。如果有任何依赖关系循环(不应存在),则可能有必要列出一个库两次。

2020-07-02