错误 - “（。text + 0x0）：'method'的多重定义”（C程序）

Question

I currently have 2 C-programs and 1 header file that I have to make into a Makefile. I am new to compiling programs into Makefiles but I know the basics. I type in:

cc -c file1.c

cc -c file2.c

cc file1.o file2.o

----- I get the following error -----

file2.o: In function 'method':

file2.c:(.text+0x0): multiple definition of 'method'

file1.o:file1.c:(.text+0x0): first defined here

collect2: ld returned 1 exit status

What is the problem? I heard various things like because they share the same header ('method' is defined in the header file) that the compiler thinks there is two of them. I don't know. What do you guys think?

Thank you,

EDIT: Thank you for the responses. What if 'method' is a "struct" function? Would it still be a good idea to just move it to somewhere else? I just tried it and now I'm getting a "dereferencing pointer to incomplete type".

Answer 1

'method' is defined in the header file.

You should not be doing that. If you do that the function definition will go into all the files that include the header which causes linking errors as there will be multiple versions of the method.

You need to only declare the method in a header file. Define it in a .c file, compile it and link it to the object file from where this function is getting called.

Answer 2

If method is a small function defined in a header file, you should declare it static inline eg like

/// in header.h
static inline int sum(int x, int y) { return x+y; }

Answer 3

Make your header file like this (the ifndef is to make sure it doesnt get included more than once):

#ifndef MYHEADER_H_
#define MYHEADER_H_

extern void mymethod1(void); // only put declaration in headers
extern void mymethod2(void);
... other stuff

#endif

Answer 4

You have definition for method in both file2.c and file1.c . Try to only put declaration in common header files and move definition to only one c file.

Answer 5

将函数声明为静态函数。