Makefile错误 - 链接器输入文件未使用(Makefile Error - Linker input file unused)

 我正在尝试运行一个看起来像这样的简单makefile： 
 
T=-ansi -pedantic -Wall -Werror
a.out: test.o extra.o
    gcc $(T) -c test.o extra.o

test.o: test.c test.h 
    gcc $(T) -c test.c

extra.o: extra.c extra.h 
    gcc $(T) -c extra.c

clean:
    rm *.o a.out
 
 但我似乎得到警告告诉我“链接器输入文件未使用，因为链接未完成” 
 
 我尝试在gcc之后从a.out指令中删除“-c”，但这会产生更多问题。 我不确定如何从这里开始，任何想法/输入将非常感激。 
 
 编辑：我正在通过“make -T”运行程序，同时从a.out中删除-c，导致错误“无效符号索引” 

I'm trying to run a simple makefile that looks like this:
 
T=-ansi -pedantic -Wall -Werror
a.out: test.o extra.o
    gcc $(T) -c test.o extra.o

test.o: test.c test.h 
    gcc $(T) -c test.c

extra.o: extra.c extra.h 
    gcc $(T) -c extra.c

clean:
    rm *.o a.out
 
But I seem to be getting warnings telling me that "linker input file unused because linking not done"
 
I tried removing the "-c" from the a.out directive, after the gcc, but that produced to give me more problems. I'm not sure how to go about proceeding from here, any ideas/input would be much appreciated.
 
EDIT: I'm running the program by "make -T", also removing the -c from a.out, causes the error" invalid symbol index"

原文：https://stackoverflow.com/questions/33137876