'_start'的多重定義

Question

我一直在弄我的makefile代碼的錯誤，我不知道如何解決這個問題，我在網站上搜索了一個答案，並最終創建了一個賬戶來尋求幫助。 這裏是錯誤代碼

date.o: In function `_start': 
(.text+0x0): multiple definition of `_start' 
/usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/crt1.o:(.text+0x0): first defined here 
date.o: In function `_fini': 
(.fini+0x0): multiple definition of `_fini' 
/usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/crti.o (.fini+0x0): first defined here 
date.o:(.rodata+0x0): multiple definition of `_IO_stdin_used' 
/usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/crt1.o (.rodata.cst4+0x0): first defined here 
date.o: In function `data_start': 
(.data+0x0): multiple definition of `__data_start' 
/usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/crt1.o:(.data+0x0): first defined here 
date.o: In function `data_start': 
(.data+0x8): multiple definition of `__dso_handle' 
/usr/lib/gcc/x86_64-linux-gnu/5/crtbegin.o:(.data+0x0): first defined here 
date.o: In function `_init': 
(.init+0x0): multiple definition of `_init' 
/usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/crti.o (.init+0x0): first defined here 
/usr/lib/gcc/x86_64-linux-gnu/5/crtend.o:(.tm_clone_table+0x0): multiple definition of `__TMC_END__' 
date.o:(.data+0x10): first defined here 
/usr/bin/ld: error in date.o(.eh_frame); no .eh_frame_hdr table will be created. 
collect2: error: ld returned 1 exit status 
Makefile:3: recipe for target 'testdate' failed 
make: *** [testdate] Error 1 

和我的makefile

testdate: date.o testdate.o 
     g++ -Wall -o testdate.o date.o 

date.o: date.h date.cpp 
     g++ -Wall -c date.cpp 
testdate.o: date.h testdate.cpp 
     g++ -Wall -c testdate.cpp 

Answer 1

規則

testdate: date.o testdate.o 
     g++ -Wall -o testdate.o date.o 

應該

testdate: date.o testdate.o 
     g++ -Wall -o testdate testdate.o date.o 
#     ^^^^^^^^ 

或避免重複自己：

testdate: date.o testdate.o 
     g++ -Wall $^ -o $@ 

（這應該產生g++ -Wall date.o testdate.o -o testdate）

事實上，你可能要考慮：

testdate: date.o testdate.o 
     g++ -Wall $^ -o $@ 
date.o: date.cpp date.h 
    g++ -Wall -c $< -o $@ 
testdate.o: testdate.cpp date.h 
    g++ -Wall -c $< -o $@ 

$^是所有的依賴關係，$<是ju st第一個和$@是當前目標。

更多關於Makefile的規則：https://www.chemie.fu-berlin.de/chemnet/use/info/make/make_4.html