加速C++:编译第4章中的程序

Accelerated C++: compiling the programs in chapter 4

本文关键字：程序 4章 C++ 编译 加速      更新时间：2023-10-16

我写了一个Makefile来编译文件并输出文件"main"，我最终将通过"./main"执行该文件。下面是我的Makefile:

CXX=clang++
CXXFLAGS=-g -std=c++11 -Wall -pedantic
BIN=prog
SRC=$(wildcard *.cpp)
OBJ=$(SRC:%.cpp=%.o)
all: Student_info median grade main
main: main.cpp
    $(CXX) $(CXXFLAGS) main.cpp -o main grade.o median.o Student_info.o
grade: grade.h grade.cpp
    $(CXX) $(CXXFLAGS) grade.cpp -o grade.o
median: median.h median.cpp
    $(CXX) $(CXXFLAGS) median.cpp -o median.o
Student_info: Student_info.h Student_info.cpp
    $(CXX) $(CXXFLAGS) Student_info.cpp -o Student_info.o
clean:
    rm -f *.o
    rm -f main

然而，它说

clang++ -g -std=c++11 -Wall -pedantic Student_info.cpp -o Student_info.o
Undefined symbols for architecture x86_64:
  "_main", referenced from:
     implicit entry/start for main executable
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [Student_info] Error 1

我的Makefile出了什么问题？

Student_info: Student_info.h Student_info.cpp
    $(CXX) $(CXXFLAGS) Student_info.cpp -o Student_info.o

看起来您希望将其编译为对象文件，而不进行链接。为此，您需要通过-c。此外，目标的名称应该是Student_info.o:

Student_info.o: Student_info.h Student_info.cpp
    $(CXX) $(CXXFLAGS) -c Student_info.cpp -o Student_info.o

grade和median同上。

main不仅应该依赖于main.cpp，还应该依赖于链接它的对象文件：

main: main.cpp Student_info.o grade.o median.o
    $(CXX) $(CXXFLAGS) main.cpp -o main grade.o median.o Student_info.o
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