In file included from hello.c:2:0:
test.c: In function 'say':
test.c:3:5: warning: implicit declaration of function 'printLine' [-Wimplicit-function-declaration]
printLine();
^~~~~~~~~
hello.c: At top level:
hello.c:3:13: warning: conflicting types for 'printLine'
extern void printLine() //这里定义的方法对吗？
^~~~~~~~~
In file included from hello.c:2:0:
test.c:3:5: note: previous implicit declaration of 'printLine' was here
printLine();
^~~~~~~~~
test.c: In function 'say':
test.c:3:5: warning: implicit declaration of function 'printLine' [-Wimplicit-function-declaration]
printLine();
^~~~~~~~~
/tmp/ccOiLhfJ.o: In function `say':
test.c:(.text+0x0): multiple definition of `say'
/tmp/ccIbjHlD.o:hello.c:(.text+0x0): first defined here
collect2: error: ld returned 1 exit status
