与共享库链接时未定义的引用

时间：2018-09-06 23:20:58

标签： c++ linker g++ static-linking

我正在尝试编写一个与共享库（* .so）链接的小程序。但是，当我尝试编译该程序时， 我收到一条错误消息，说“未定义引用”指向“函数”

程序文件的内容。

user@ubuntu:~/Perforce/user_ubuntu_3105/wp/eng/main/src/libfc/37D03B6/bin$ cat test.cpp 
#include <iostream>
#include <vector>
#include <memory>
#include "InfoModel.h"

int main() 
{
    libfc::InfoModel & model = libfc::InfoModel::instance();
    return 0;
}

对此进行编译，我得到错误“未定义的引用” 

user@ubuntu:~/Perforce/user_ubuntu_3105/wp/eng/main/src/libfc/37D03B6/bin$ g++ -Wall -W -std=c++0x test.cpp -L. -lfc -o rst
test.cpp: In function ‘int main()’:
test.cpp:9:21: warning: unused variable ‘model’ [-Wunused-variable]
libfc::InfoModel & model = libfc::InfoModel::instance();
                 ^
/tmp/ccFtLDxc.o: In function `main':
test.cpp:(.text+0x9): undefined reference to `libfc::InfoModel::instance()'
collect2: error: ld returned 1 exit status

但是当我查看.so文件中的符号时，在那里看到了该符号。 

user@ubuntu:~/Perforce/user_ubuntu_3105/wp/eng/main/src/libfc/37D03B6/bin$ nm --demangle libfc.so | grep InfoModel 
0000000000007e40 t _GLOBAL__sub_I_InfoModel.cpp
00000000002464a0 b guard variable for libfc::InfoModel::instance()::instance_
0000000000010260 t libfc::InfoModel::add_unknown(unsigned int, unsigned short, unsigned short)
0000000000010520 t libfc::InfoModel::registerIEType(libfc::IEType const*)
000000000000f550 t libfc::InfoModel::add(libfc::InfoElement const&)
0000000000012980 t libfc::InfoModel::add(std::string const&)
0000000000010a60 t libfc::InfoModel::instance()
00000000000106f0 t libfc::InfoModel::initTypes()
00000000000108f0 t libfc::InfoModel::InfoModel()
00000000000108f0 t libfc::InfoModel::InfoModel()
0000000000027ae0 t libfc::InfoModel::~InfoModel()
0000000000027ae0 t libfc::InfoModel::~InfoModel()
0000000000010b00 t libfc::InfoModel::parseIESpec(std::string const&) const
000000000000ee80 t libfc::InfoModel::lookupIEType(unsigned int) const
000000000000ed40 t libfc::InfoModel::lookupIEType(std::string const&) const
000000000000ef20 t libfc::InfoModel::dump(std::ostream&) const
000000000000f0c0 t libfc::InfoModel::lookupIE(unsigned int, unsigned short, unsigned short) const
000000000000f1b0 t libfc::InfoModel::lookupIE(libfc::InfoElement const&) const
0000000000012840 t libfc::InfoModel::lookupIE(std::string const&) const
000000000000f410 t libfc::InfoModel::lookupIE2(unsigned int, std::string const&, unsigned short, unsigned short) const
00000000002463a0 b libfc::InfoModel::instance()::instance_

我也这样做了。

user@ubuntu:~/Perforce/user_ubuntu_3105/wp/eng/main/src/libfc/37D03B6/bin$ readelf -s libfc.so | grep FILE 
34: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS EncodePlan.cpp
43: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS InfoElement.cpp
49: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS FileExportDestination.cpp
53: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS IETemplate.cpp
58: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS IEType.cpp
104: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS InfoModel.cpp
113: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS libfc.cpp
118: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS PlacementExporter2.cpp
124: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS PlacementTemplate.cpp
129: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS TemplateState.cpp
135: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS test.cpp
141: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS UdpSocketExportDestinatio
149: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS crtstuff.c
158: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS BasicOctetArray.cpp
159: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS Exception.cpp
160: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS ExportError.cpp
161: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS FormatError.cpp
162: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS IESpecError.cpp
163: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS error_code.cpp
187: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS crtstuff.c
190: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS

更新： 构建此共享库的make文件是

PLUGIN          = libfc
OUTPUT_DIR      = bin
OUTPUT          = $(OUTPUT_DIR)/$(PLUGIN).so
PLUG_SRC        = src
EXCEPTION_SRC   = src/exceptions
CPP             = g++
THIRD_PARTY_DIR = ../../../../../third-party
BOOST_DIR       = $(THIRD_PARTY_DIR)/boost/1.66.0
G3LOG_DIR       = $(THIRD_PARTY_DIR)/g3log/2017-07-18_g3log
FLAGS           = -c -std=c++0x -fvisibility-inlines-hidden -pthread \
              -fPIC -fvisibility=hidden -fno-omit-frame-pointer -fpermissive 
MACROS          = -D_libfc_HAVE_NIXIO -U_libfc_HAVE_LOG4CPLUS_ -U_libfc_HAVE_WANDIO_
INCLUDES        = -I$(PLUG_SRC) \
              -I$(EXCEPTION_SRC) \
              -I$(BOOST_DIR) \
              -I$(G3LOG_DIR)/src \
              -I$(G3LOG_DIR)/include
LFLAGS          = -shared -lpthread -L$(G3LOG_DIR)/build -lg3logger
CPPFLAGS     = $(FLAGS) $(MACROS) $(INCLUDES)  
LDFLAGS      = $(LFLAGS)
ifeq ($(BUILD),DEBUG)
CPPFLAGS += -ggdb3 -O0 
else
CPPFLAGS += -g -Wall -O2 -D NDEBUG
LDFLAGS += -flto 
endif

# compile static boost lib as
# ./bjam --toolset=gcc address-model=64 cxxflags=-fPIC cflags=-fPIC 
variant=release threading=multi link=static --with-system stage
BOOST_LIBS      = $(BOOST_DIR)/stage/lib/libboost_system.a
OBJ_DIR         = obj
PLUG_OBJS       = $(patsubst %.cpp,$(OBJ_DIR)/%.o,$(subst 
$(PLUG_SRC)/,,$(wildcard $(PLUG_SRC)/*.cpp)))
FRAME_OBJS      = $(patsubst %.cpp,$(OBJ_DIR)/%.o,$(subst 
$(EXCEPTION_SRC)/,,$(wildcard $(EXCEPTION_SRC)/*.cpp)))
VPATH           = $(PLUG_SRC) $(EXCEPTION_SRC)

all: $(PLUGIN)
$(PLUG_OBJS): $(OBJ_DIR)/%.o: %.cpp
   $(CPP) $(CPPFLAGS) -o $@ $<
$(FRAME_OBJS): $(OBJ_DIR)/%.o: %.cpp
   $(CPP) $(CPPFLAGS) -o $@ $<
$(PLUG_OBJS) $(FRAME_OBJS): | $(OBJ_DIR)
$(OBJ_DIR):
   mkdir $(OBJ_DIR)
$(OUTPUT): | $(OUTPUT_DIR)
$(OUTPUT_DIR):
   mkdir $(OUTPUT_DIR)
$(PLUGIN): $(PLUG_OBJS) $(FRAME_OBJS) $(OUTPUT)
   $(CPP) $(LDFLAGS) -o $(OUTPUT)  $(PLUG_OBJS) $(FRAME_OBJS) $(BOOST_LIBS)

.PHONY: clean
clean:
   rm -f $(PLUG_OBJS) $(FRAME_OBJS) $(OUTPUT)
   rm -rf $(OBJ_DIR)
   rm -rf $(OUTPUT_DIR)

make的输出为

user@ubuntu:~/Perforce/sselvam_ubuntu_3105/wp/eng/main/src/libfc/37D03B6$ make all 
mkdir obj
g++ -c -std=c++0x -fvisibility-inlines-hidden -pthread -fPIC -fvisibility=hidden -fno-omit-frame-pointer -fpermissive  -D_libfc_HAVE_NIXIO -U_libfc_HAVE_LOG4CPLUS_ -U_libfc_HAVE_WANDIO_ -Isrc -Isrc/exceptions -I../../../../../third-party/boost/1.66.0 -I../../../../../third-party/g3log/2017-07-18_g3log/src -I../../../../../third-party/g3log/2017-07-18_g3log/include -g -Wall -O2 -D NDEBUG -o obj/BasicOctetArray.o src/BasicOctetArray.cpp
g++ -c -std=c++0x -fvisibility-inlines-hidden -pthread -fPIC -fvisibility=hidden -fno-omit-frame-pointer -fpermissive  -D_libfc_HAVE_NIXIO -U_libfc_HAVE_LOG4CPLUS_ -U_libfc_HAVE_WANDIO_ -Isrc -Isrc/exceptions -I../../../../../third-party/boost/1.66.0 -I../../../../../third-party/g3log/2017-07-18_g3log/src -I../../../../../third-party/g3log/2017-07-18_g3log/include -g -Wall -O2 -D NDEBUG -o obj/EncodePlan.o src/EncodePlan.cpp
src/EncodePlan.cpp: In constructor ‘libfc::EncodePlan2::EncodePlan2(const libfc::PlacementTemplate*)’:
src/EncodePlan.cpp:90:9: warning: unused variable ‘ie_present’ [-Wunused-variable]
bool ie_present
     ^
g++ -c -std=c++0x -fvisibility-inlines-hidden -pthread -fPIC -fvisibility=hidden -fno-omit-frame-pointer -fpermissive  -D_libfc_HAVE_NIXIO -U_libfc_HAVE_LOG4CPLUS_ -U_libfc_HAVE_WANDIO_ -Isrc -Isrc/exceptions -I../../../../../third-party/boost/1.66.0 -I../../../../../third-party/g3log/2017-07-18_g3log/src -I../../../../../third-party/g3log/2017-07-18_g3log/include -g -Wall -O2 -D NDEBUG -o obj/FileExportDestination.o src/FileExportDestination.cpp
g++ -c -std=c++0x -fvisibility-inlines-hidden -pthread -fPIC -fvisibility=hidden -fno-omit-frame-pointer -fpermissive  -D_libfc_HAVE_NIXIO -U_libfc_HAVE_LOG4CPLUS_ -U_libfc_HAVE_WANDIO_ -Isrc -Isrc/exceptions -I../../../../../third-party/boost/1.66.0 -I../../../../../third-party/g3log/2017-07-18_g3log/src -I../../../../../third-party/g3log/2017-07-18_g3log/include -g -Wall -O2 -D NDEBUG -o obj/IETemplate.o src/IETemplate.cpp
 g++ -c -std=c++0x -fvisibility-inlines-hidden -pthread -fPIC -fvisibility=hidden -fno-omit-frame-pointer -fpermissive  -D_libfc_HAVE_NIXIO -U_libfc_HAVE_LOG4CPLUS_ -U_libfc_HAVE_WANDIO_ -Isrc -Isrc/exceptions -I../../../../../third-party/boost/1.66.0 -I../../../../../third-party/g3log/2017-07-18_g3log/src -I../../../../../third-party/g3log/2017-07-18_g3log/include -g -Wall -O2 -D NDEBUG -o obj/IEType.o src/IEType.cpp
 g++ -c -std=c++0x -fvisibility-inlines-hidden -pthread -fPIC -fvisibility=hidden -fno-omit-frame-pointer -fpermissive  -D_libfc_HAVE_NIXIO -U_libfc_HAVE_LOG4CPLUS_ -U_libfc_HAVE_WANDIO_ -Isrc -Isrc/exceptions -I../../../../../third-party/boost/1.66.0 -I../../../../../third-party/g3log/2017-07-18_g3log/src -I../../../../../third-party/g3log/2017-07-18_g3log/include -g -Wall -O2 -D NDEBUG -o obj/InfoElement.o src/InfoElement.cpp
g++ -c -std=c++0x -fvisibility-inlines-hidden -pthread -fPIC -fvisibility=hidden -fno-omit-frame-pointer -fpermissive  -D_libfc_HAVE_NIXIO -U_libfc_HAVE_LOG4CPLUS_ -U_libfc_HAVE_WANDIO_ -Isrc -Isrc/exceptions -I../../../../../third-party/boost/1.66.0 -I../../../../../third-party/g3log/2017-07-18_g3log/src -I../../../../../third-party/g3log/2017-07-18_g3log/include -g -Wall -O2 -D NDEBUG -o obj/InfoModel.o src/InfoModel.cpp
g++ -c -std=c++0x -fvisibility-inlines-hidden -pthread -fPIC -fvisibility=hidden -fno-omit-frame-pointer -fpermissive  -D_libfc_HAVE_NIXIO -U_libfc_HAVE_LOG4CPLUS_ -U_libfc_HAVE_WANDIO_ -Isrc -Isrc/exceptions -I../../../../../third-party/boost/1.66.0 -I../../../../../third-party/g3log/2017-07-18_g3log/src -I../../../../../third-party/g3log/2017-07-18_g3log/include -g -Wall -O2 -D NDEBUG -o obj/libfc.o src/libfc.cpp
g++ -c -std=c++0x -fvisibility-inlines-hidden -pthread -fPIC -fvisibility=hidden -fno-omit-frame-pointer -fpermissive  -D_libfc_HAVE_NIXIO -U_libfc_HAVE_LOG4CPLUS_ -U_libfc_HAVE_WANDIO_ -Isrc -Isrc/exceptions -I../../../../../third-party/boost/1.66.0 -I../../../../../third-party/g3log/2017-07-18_g3log/src -I../../../../../third-party/g3log/2017-07-18_g3log/include -g -Wall -O2 -D NDEBUG -o obj/PlacementExporter2.o src/PlacementExporter2.cpp
g++ -c -std=c++0x -fvisibility-inlines-hidden -pthread -fPIC -fvisibility=hidden -fno-omit-frame-pointer -fpermissive  -D_libfc_HAVE_NIXIO -U_libfc_HAVE_LOG4CPLUS_ -U_libfc_HAVE_WANDIO_ -Isrc -Isrc/exceptions -I../../../../../third-party/boost/1.66.0 -I../../../../../third-party/g3log/2017-07-18_g3log/src -I../../../../../third-party/g3log/2017-07-18_g3log/include -g -Wall -O2 -D NDEBUG -o obj/PlacementTemplate.o src/PlacementTemplate.cpp
g++ -c -std=c++0x -fvisibility-inlines-hidden -pthread -fPIC -fvisibility=hidden -fno-omit-frame-pointer -fpermissive  -D_libfc_HAVE_NIXIO -U_libfc_HAVE_LOG4CPLUS_ -U_libfc_HAVE_WANDIO_ -Isrc -Isrc/exceptions -I../../../../../third-party/boost/1.66.0 -I../../../../../third-party/g3log/2017-07-18_g3log/src -I../../../../../third-party/g3log/2017-07-18_g3log/include -g -Wall -O2 -D NDEBUG -o obj/TemplateState.o src/TemplateState.cpp
g++ -c -std=c++0x -fvisibility-inlines-hidden -pthread -fPIC -fvisibility=hidden -fno-omit-frame-pointer -fpermissive  -D_libfc_HAVE_NIXIO -U_libfc_HAVE_LOG4CPLUS_ -U_libfc_HAVE_WANDIO_ -Isrc -Isrc/exceptions -I../../../../../third-party/boost/1.66.0 -I../../../../../third-party/g3log/2017-07-18_g3log/src -I../../../../../third-party/g3log/2017-07-18_g3log/include -g -Wall -O2 -D NDEBUG -o obj/UdpSocketExportDestination.o src/UdpSocketExportDestination.cpp
g++ -c -std=c++0x -fvisibility-inlines-hidden -pthread -fPIC -fvisibility=hidden -fno-omit-frame-pointer -fpermissive  -D_libfc_HAVE_NIXIO -U_libfc_HAVE_LOG4CPLUS_ -U_libfc_HAVE_WANDIO_ -Isrc -Isrc/exceptions -I../../../../../third-party/boost/1.66.0 -I../../../../../third-party/g3log/2017-07-18_g3log/src -I../../../../../third-party/g3log/2017-07-18_g3log/include -g -Wall -O2 -D NDEBUG -o obj/Exception.o src/exceptions/Exception.cpp
g++ -c -std=c++0x -fvisibility-inlines-hidden -pthread -fPIC -fvisibility=hidden -fno-omit-frame-pointer -fpermissive  -D_libfc_HAVE_NIXIO -U_libfc_HAVE_LOG4CPLUS_ -U_libfc_HAVE_WANDIO_ -Isrc -Isrc/exceptions -I../../../../../third-party/boost/1.66.0 -I../../../../../third-party/g3log/2017-07-18_g3log/src -I../../../../../third-party/g3log/2017-07-18_g3log/include -g -Wall -O2 -D NDEBUG -o obj/ExportError.o src/exceptions/ExportError.cpp
g++ -c -std=c++0x -fvisibility-inlines-hidden -pthread -fPIC -fvisibility=hidden -fno-omit-frame-pointer -fpermissive  -D_libfc_HAVE_NIXIO -U_libfc_HAVE_LOG4CPLUS_ -U_libfc_HAVE_WANDIO_ -Isrc -Isrc/exceptions -I../../../../../third-party/boost/1.66.0 -I../../../../../third-party/g3log/2017-07-18_g3log/src -I../../../../../third-party/g3log/2017-07-18_g3log/include -g -Wall -O2 -D NDEBUG -o obj/FormatError.o src/exceptions/FormatError.cpp
g++ -c -std=c++0x -fvisibility-inlines-hidden -pthread -fPIC -fvisibility=hidden -fno-omit-frame-pointer -fpermissive  -D_libfc_HAVE_NIXIO -U_libfc_HAVE_LOG4CPLUS_ -U_libfc_HAVE_WANDIO_ -Isrc -Isrc/exceptions -I../../../../../third-party/boost/1.66.0 -I../../../../../third-party/g3log/2017-07-18_g3log/src -I../../../../../third-party/g3log/2017-07-18_g3log/include -g -Wall -O2 -D NDEBUG -o obj/IESpecError.o src/exceptions/IESpecError.cpp
mkdir bin
g++ -shared -lpthread -L../../../../../third-party/g3log/2017-07-18_g3log/build -lg3logger -flto  -o bin/libfc.so  obj/BasicOctetArray.o obj/EncodePlan.o obj/FileExportDestination.o obj/IETemplate.o obj/IEType.o obj/InfoElement.o obj/InfoModel.o obj/libfc.o obj/PlacementExporter2.o obj/PlacementTemplate.o obj/TemplateState.o obj/UdpSocketExportDestination.o obj/Exception.o obj/ExportError.o obj/FormatError.o obj/IESpecError.o ../../../../../third-party/boost/1.66.0/stage/lib/libboost_system.a

任何帮助都会非常有帮助。

1 个答案:

答案 0 :(得分：0)

libfc::InfoModel & model = libfc::InfoModel::instance();
                 ^
/tmp/ccFtLDxc.o: In function `main':
test.cpp:(.text+0x9): undefined reference to `libfc::InfoModel::instance()'
collect2: error: ld returned 1 exit status

与-fvisibility=hidden（和朋友）结合使用：

$ nm -gCD ...

0000000000012980 t libfc::InfoModel::add(std::string const&)
0000000000010a60 t libfc::InfoModel::instance()
00000000000106f0 t libfc::InfoModel::initTypes()
...

我相信所有这些意味着您已经隐藏了InfoModel类，并且该类不再可见。我猜您是手动添加了-fvisibility=hidden（和朋友），但是没有编辑源文件并添加了DLL_PUBLIC（根据GCC Visibility Wiki）。

我认为对您来说最简单的解决方法是在没有可见性的情况下构建静态档案。也就是说，请勿使用-fvisibility=hidden（和朋友）。然后，在构建使用静态档案的共享库/插件时，请使用-fvisibility=hidden（和朋友）并包括-Wl,--exclude-libs,ALL链接器标志。额外的链接器标志将确保您不会从静态归档文件中重新导出符号。

您的插件源文件将使用DLL_PUBLIC（根据GCC Visibility Wiki）。 Makefile配方将使用类似以下内容的

： 
$(PLUGIN): $(PLUG_OBJS) $(FRAME_OBJS) $(OUTPUT)
   $(CXX) -shared -o $(OUTPUT) $(CXXFLAGS) $(PLUG_OBJS) $(FRAME_OBJS) $(BOOST_LIBS) $(LDFLAGS) -Wl,--exclude-libs,ALL

然后，您可以使用以下方法检查从共享库/插件中导出的内容：

nm -gCD libplugin.so | grep ' T '

不幸的是，无法避免nm -gCD libplugin.so | grep ' T '疣。我只是在Binutils邮件列表中，正在寻找一种更好的方式来显示导出内容。

最近针对这些文档打开了GCC问题报告，以在Issue 87190, Feedback on documentation for symbol visibility进行公开。另请参阅Binutils邮件列表上的Linker exposing private symbols。

一些其他快速评论... 

CPP = g++

CPP是预处理器。使用CXX。

FLAGS = ...

对C ++项目使用CXXFLAGS。您的C ++配方可能如下所示：

SRCS = $(sort $(wildcard *.cpp))
OBJS = $(SRCS:.cpp=.o)

%.o : %.cpp
    $(CXX) $(CPPFLAGS) $(CXXFLAGS) -c $<
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