Make期间的链接器错误

Question

我编写了一个在 Eclipse 中运行良好的 c++ 项目。 但是当尝试使用 makefile 进行编译时，我得到了一个错误。 当我搜索此错误时，所有解决方案都建议添加主要功能。 我在 matrixU.cpp 中有一个 main 函数。

这是制作文件：

# All Targets
all: matrixU

# Tool invocations
# Executable "matrixU" depends on the files matrixU.o and Student.o and Course.o
matrixU: bin/matrixU.o bin/Student.o bin/Course.o
    @echo 'Building target: matrixU'
    @echo 'Invoking: C++ Linker'
    g++ -o bin/matrixU.o bin/Student.o bin/Course.o
    @echo 'Finished building target: matrixU'
    @echo ' '

# Depends on the source and header files
bin/matrixU.o: src/matrixU.cpp include/matrixU.h
    g++ -g -Wall -Weffc++ -c -Linclude -o bin/matrixU.o src/matrixU.cpp

# Depends on the source and header files 
bin/Student.o: src/Student.cpp include/Student.h
    g++ -g -Wall -Weffc++ -c -Linclude -o bin/Student.o src/Student.cpp

# Depends on the source and header files 
bin/Course.o: src/Course.cpp include/Course.h
    g++ -g -Wall -Weffc++ -c -Linclude -o bin/Course.o src/Course.cpp

#Clean the build directory
clean: 
    rm -rf bin/*

这是错误：

/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 0 has invalid symbol index 10
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 1 has invalid symbol index 11
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 2 has invalid symbol index 2
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 3 has invalid symbol index 2
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 4 has invalid symbol index 10
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 5 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 6 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 7 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 8 has invalid symbol index 2
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 9 has invalid symbol index 2
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 10 has invalid symbol index 11
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 11 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 12 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 13 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 14 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 15 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 16 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 17 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 18 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 19 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 20 has invalid symbol index 19
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crt1.o: In function `_start':
(.text+0x20): undefined reference to `main'
collect2: ld returned 1 exit status

Answer 1

 g++ -o bin/matrixU.o bin/Student.o bin/Course.o

这一行将bin/matrixU.o（您之前从源代码编译）定义为输出文件，从而导致损坏。

你想要的是将三个 *.o input 文件链接到一个 different 输出文件中，它应该与规则的目标相同，就像这样：

 g++ -o bin/matrixU bin/matrixU.o bin/Student.o bin/Course.o

另外，我可以谦虚地建议将头依赖项留给编译器，并使用模式匹配构建规则，这样您就不必每次添加/删除文件或依赖项时都编辑 Makefile。

我为此写了一个tutorial，但它的简短版本是：

# Assuming GNU make
SRCFILES := $(shell find $(PROJDIRS) -type f -name "\*.cpp")
DEPFILES := $(patsubst src/%.cpp,bin/%.d,$(SRCFILES))
OBJFILES := $(patsubst src/%.cpp,bin/%.o,$(SRCFILES))
CXXFLAGS_LOCAL := -g -Wall -Weffc++ -Linclude

.PHONY: all clean

all: matrixU

clean: 
    rm -rf bin/*

-include $(DEPFILES)

matrixU: $(OBJFILES)
    $(CXX) -o $@ $^

bin/%.o: src/%.cpp
    $(CXX) $(CXXFLAGS_LOCAL) $(CXXFLAGS) -MMD -MP -c $< -o $@

Answer 2

这条规则看起来很可疑：

matrixU: bin/matrixU.o bin/Student.o bin/Course.o
    @echo 'Building target: matrixU'
    @echo 'Invoking: C++ Linker'
    g++ -o bin/matrixU.o bin/Student.o bin/Course.o
    @echo 'Finished building target: matrixU'
    @echo ' '

您依赖于bin/matrixU.o，并创建了一个同名文件。你可能需要

matrixU: bin/matrixU.o bin/Student.o bin/Course.o
    @echo 'Building target: matrixU'
    @echo 'Invoking: C++ Linker'
    g++  bin/matrixU.o bin/Student.o bin/Course.o -o matrixU
    @echo 'Finished building target: matrixU'
    @echo ' '

即

g++  bin/matrixU.o bin/Student.o bin/Course.o -o matrixU

而不是

g++ -o bin/matrixU.o bin/Student.o bin/Course.o

但是您应该使用宏 $@ 和 $^ 来代替，它们解析为目标，即规则中 : 左侧的内容，以及右侧的依赖项的:，分别。这样可以防止一些错误：

matrixU: bin/matrixU.o bin/Student.o bin/Course.o
    g++  $^ -o $@