Cannot link LIBEVENT as C++

Question

Why this does not work, file test.c:

#include <event.h>
int main(void)
{
    event_init();
    return 0;
}

Then: gcc -o test.o -c test.c runs OK, but

Link: g++ -o test -levent test.o produces

test.o: In function `main':
test.c:(.text+0x5): undefined reference to `event_init'
collect2: ld returned 1 exit status

So it cannot be linked as C++. How to solve this? I need to link it as C++ and compile as C.

Yes, order matters a lot – Basile Starynkevitch Nov 18 '11 at 17:08 — Basile Starynkevitch, Nov 18 '11 at 17:08
Try `g++ -o test test.o -levent`. – Kerrek SB Nov 18 '11 at 17:08 — Kerrek SB, Nov 18 '11 at 17:08

Basile Starynkevitch · Accepted Answer · 2011-11-18T17:20:25.333

14

This question has been asked many times. On Linux, you should put libraries after object and source files in the compilation command. So try

g++ -Wall -g -c mytest.cc 
g++ -Wall -g mytest.o -levent -o mytest

Avoid calling your test program test which is an existing utility or shell builtin.

As a newbie, remember to always compile with all warnings asked -Wall and for debugging -g and learn to use gdb

edited Nov 18 '11 at 17:20

answered Nov 18 '11 at 17:07

2

I object that compiler warnings and debuggers are "newbie" tools. Compiler warnings should be mandatory for *everyone*. – Kerrek SB Nov 18 '11 at 17:13
1

Sorry, I did not mean that (remember, I am not a native English speaker). I just meant that newbies often forget to enable warnings and debugging. Once you are more skilled in C or C++ programming, you won't forget them! – Basile Starynkevitch Nov 18 '11 at 17:16
Yes, that makes sense. "As a newbie, *remember to enable* ..." :-) – Kerrek SB Nov 18 '11 at 17:19
If the question has been asked many times, why did you bother answering it? – netcoder Nov 18 '11 at 17:24
Because it is Friday evening (in Paris), and I have some time... :-) :-) – Basile Starynkevitch Nov 18 '11 at 17:25
2

Explanation of *why* libraries after objects rule: http://webpages.charter.net/ppluzhnikov/linker.html – Employed Russian Nov 18 '11 at 17:48

1 Answers1