error LNK1169: one or more multiply defined symbols found - global function

Question

I have this:

a.h:

class a
{
}
void func(){} //some golobal function

b.h:

include "a.h"
class b : public a
{
}

b.cpp:

#include "b.h"

I get the error:

error LNK1169: one or more multiply defined symbols found

I think I get the error because global function defined twice. I try to put extern before the function but is doesnt work. I use also #ifndef.. and I still get error. How can solve this problem?

Compiler lists the symbols which are multiply defined. What are those symbols? — doptimusprime, Jun 10 '14 at 09:51
If the definition of `func` is included twice in b.cpp file, compiler would have given an error while compiling the file. — doptimusprime, Jun 10 '14 at 09:52
possible duplicate [Should one use forward declarations instead of includes wherever possible?](http://stackoverflow.com/questions/9906402/should-one-use-forward-declarations-instead-of-includes-wherever-possible) — Ivan Solntsev, Jun 10 '14 at 09:53

score 3 · Answer 1 · answered Jun 10 '14 at 09:50

3

You have either only to declare the function in header a.h and define it in some cpp module or define it as an inline function. For example

inline void func(){}

Otherwise the function will be defined as many times as there are cpp modules that include either header a.h or b.h.

answered Jun 10 '14 at 09:50

Vlad from Moscow

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I still cannot deduce why this would solve a problem. Any way, a.h is included once and only in one compilation unit. – doptimusprime Jun 10 '14 at 09:55
@dbasic And what about the module that contains function main? Does it include either a.h or b.h? – Vlad from Moscow Jun 10 '14 at 09:56
This program may or may not contain main depending whether it is application or some library. It must be mentioned in the question. – doptimusprime Jun 10 '14 at 09:58
@dbasic if the linker issued the error it means that at least two modules contain the function definition. – Vlad from Moscow Jun 10 '14 at 09:59
You are right. But whole error message is missing from the question. It might be some other symbols as well. Compiler also says about the symbols which are duplicate. – doptimusprime Jun 10 '14 at 10:02

error LNK1169: one or more multiply defined symbols found - global function

1 Answers1