undefined reference to extern variable

Asked Oct 24 '16 at 03:39

Active Oct 25 '16 at 20:01

Viewed 35 times

I'm trying to use an extern file pointer declared in a header file in two different .cpp files. The following code is a reduced version of my project, but the logic is the same:

file2.h:

extern FILE* output;
void print_stuff();

file1.cpp:

#include "file2.h"
int main() {
    output = fopen("hello.txt", "w");
    print_stuff();
}

file2.cpp

void print_stuff() {
    fprintf(output, "hello\n");
}

however, I'm getting undefined reference errors to the output filepointer in both cpp files. Is there something I'm doing wrong?

edited Oct 25 '16 at 20:01

asked Oct 24 '16 at 03:39

Philip

1

You need to define it in `file2.cpp`, like `FILE* output;`. – songyuanyao Oct 24 '16 at 03:40
thanks, that worked! – Philip Oct 24 '16 at 03:42
This question should not have been tagged C. Only use the C tag for code that is intended to be compiled with a C (not C++) compiler. – Brian Bi Oct 24 '16 at 03:46
removed the tag – Philip Oct 25 '16 at 20:01

undefined reference to extern variable

0 Answers0