Undefined reference to second function

Asked Feb 17 '16 at 13:51

Active Feb 17 '16 at 14:02

Viewed 30 times

Have following header (and correspondent cpp) in project:

#include <string>
#include <vector>

#ifndef STRINGWORK_H
#define STRINGWORK_H

using namespace std;

vector<string> split(const string& str, const string &delimiters = " ");
string trim(string &str);

#endif // STRINGWORK_H

Building project returns linker error:

file.cpp:21: error: undefined reference to `trim(std::string&)'

if I add extern "C" to 2nd function, project builds fine. If I also add extern "C" to first function, get linker error again but for the 1st function:

file.cpp:16: error: undefined reference to `split'

What is the problem here? How to correctly declare such functions?

What is an undefined reference/unresolved external symbol error and how do I fix it? - does not explain things, and does not help as here we have C/C++ mixed code.

edited May 23 '17 at 10:28

Community

asked Feb 17 '16 at 13:51

Aleksey Kontsevich

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You should not use `using namespace std;` in a header file. Also see: [Why is “using namespace std;” considered bad practice?](http://stackoverflow.com/questions/1452721/why-is-using-namespace-std-considered-bad-practice) – NathanOliver Feb 17 '16 at 13:53
No, this does not affect things here. – Aleksey Kontsevich Feb 17 '16 at 13:56
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I know that. I was just telling you you should not do that. It is bad practice and can lead to some interesting compiler errors. – NathanOliver Feb 17 '16 at 13:58
vote to reopen as suggested things does not cover this case, suggested things do not help. – Aleksey Kontsevich Feb 17 '16 at 14:08
1

Could you post the CPP file? Do you add 'extern "C"' to the function definitions in the CPP file as well? – mmmmmmmm Feb 17 '16 at 14:39
No, I had not. Added now, builds fine. Thanks. Good to add above comment to the answer. – Aleksey Kontsevich Feb 17 '16 at 14:53

Undefined reference to second function

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