我的项目目录如下:
FooProj和BarProj是shared-libraries项目(编译为so文件)。
[问题是,当bar.cpp从foo.h调用一个函数时(位于另一个共享库中),我在main.cpp上收到编译错误,该错误表明未定义对foo()的引用。
g++ -std=c++14 -rdynamic -g -I../FooProj/ -I../BarProj/ -L../libs/ main.cpp -o ../bins/run -lFooProj -lBarProj
../libs//libBarProj.so: undefined reference to `foo()'
collect2: error: ld returned 1 exit status
makefile:5: recipe for target 'all' failed
make[1]: *** [all] Error 1
make[1]: Leaving directory '/builds/test/MainProj'
makefile:2: recipe for target 'all' failed
make: *** [all] Error 2
这是我的编码文件:
//foo.h
#ifndef _FOO_
#define _FOO_
void foo();
#endif
//foo.cpp
#include "foo.h"
#include <iostream>
void foo() { std::cout << "foo" << std::endl; }
FooProj的makefile
SHELL = /bin/sh
CXX = g++
CXXFLAGS = -std=c++14 -rdynamic -fPIC -g
LDFLAGS = -shared
TARGET = ../libs/libFooProj.so
SOURCES = $(shell echo *.cpp)
HEADERS = $(shell echo *.h)
OBJECTS = $(SOURCES:.cpp=.o)
PREFIX = $(DESTDIR)/usr/local
BINDIR = $(PREFIX)/bin
all: $(TARGET)
$(TARGET): $(OBJECTS) $(HEADERS)
$(CXX) $(CXXFLAGS) $(LDFLAGS) -o $(TARGET) $(OBJECTS) $(HEADERS)
。
//bar.h
#ifndef _BAR_
#define _BAR_
void bar();
#endif
//bar.cpp
#include "bar.h"
#include "foo.h"
#include <iostream>
void bar()
{
std::cout << "bar" << std::endl;
std::cout << "call foo function:" << std::endl;
foo();
}
BarProj的makefile
SHELL = /bin/sh
CXX = g++
CXXFLAGS = -std=c++14 -rdynamic -pthread -fPIC -g -L../libs/ -lFooProj -I../FooProj/
LDFLAGS = -shared
TARGET = ../libs/libBarProj.so
SOURCES = $(shell echo *.cpp)
HEADERS = $(shell echo *.h)
OBJECTS = $(SOURCES:.cpp=.o)
PREFIX = $(DESTDIR)/usr/local
BINDIR = $(PREFIX)/bin
all: $(TARGET)
$(TARGET): $(OBJECTS) $(HEADERS)
$(CXX) $(CXXFLAGS) $(LDFLAGS) -o $(TARGET) $(OBJECTS) $(HEADERS)
main.cpp
#include "bar.h"
int main()
{
bar();
return 0;
}
MainProj的makefile:
#include "bar.h"
int main()
{
bar();
return 0;
}
整个项目的makefile:
all:
$(MAKE) all -C FooProj/
$(MAKE) all -C BarProj/
$(MAKE) all -C MainProj/
我应如何解决此问题?我不明白为什么我的BarProj共享库无法从FooProj调用函数。
问题出在BarProj的makefile上。我从CXXFLAGS中删除了-lFooProj,并将其放在行尾:
$(CXX) $(CXXFLAGS) $(LDFLAGS) -o $(TARGET) $(OBJECTS) $(HEADERS)
解决了问题。
BarProj的完整makefile:
SHELL = /bin/sh
CXX = g++
CXXFLAGS = -std=c++14 -rdynamic -pthread -fPIC -g -L../libs/ -I../FooProj/
LDFLAGS = -shared
TARGET = ../libs/libBarProj.so
SOURCES = $(shell echo *.cpp)
HEADERS = $(shell echo *.h)
OBJECTS = $(SOURCES:.cpp=.o)
PREFIX = $(DESTDIR)/usr/local
BINDIR = $(PREFIX)/bin
all: $(TARGET)
$(TARGET): $(OBJECTS) $(HEADERS)
$(CXX) $(CXXFLAGS) $(LDFLAGS) -o $(TARGET) $(OBJECTS) $(HEADERS) -lFooProj