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.
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
Related
This may be a bit of a weird request but I'm trying to compile some software with g++ with the -nostdlib flag.
I'm pretty new to c++ and I'm still learning how linking and compiling works but I'm trying to compile this code:
#include "../lib/gamesys/types.h"
int main() {
types::setUid(1001);
}
Using these commands:
g++ -Wall -g -c bin/scripttwo.cpp -o bin/scripttwo.o -std=c++14
and
g++ -o bin/scripttwo bin/scripttwo.o software/*.o hardware/*.o *.o -nostdlib -Llib/lib/ -ltypes -ljsoncpp -lreadline -ltypes
and I'm getting the error:
/usr/bin/ld: software/FS.o: undefined reference to symbol '_Unwind_Resume##GCC_3.0'
/usr/bin/ld: /lib64/libgcc_s.so.1: error adding symbols: DSO missing from command line
I'm assuming it has something to do with the stdlib because once I remove -nostdlib, it compiles and links fine.
How can I solve this (it is pretty important that I don't include stdlibs)
Note: If you want to know why I'm trying to avoid stdlibs, let me know, its a long a convoluted story lol
I am using Netbeans for my C++ project. I compiled my program using make and ran into this error:
collect2: error: ld terminated with signal 11 [Segmentation fault], core dumped
Makefile:4: recipe for target 'barn' failed
make: *** [barn] Error 1
Whereas, when I compiled it in a linux environment(Ubuntu to be precise), it compiled fine. What could have possibly gone wrong?
This is what I got when I typed make -n:
g++ -c main.cc
g++ -c Animal.cc
g++ -c Bird.cc
g++ -c Chicken.cc
g++ -c Cat.cc
g++ -c Pig.cc
g++ -o barn main.o Animal.o Bird.o Chicken.o Cat.o Pig.o Random.o
PS I prefer using Netbeans
A segment fault in the linker suggests a bug with that. This is what I would try if I were to run into this problem.
At the command line do
g++ -o barn main.cc Animal.cc Bird.cc Chicken.cc Cat.cc Pig.cc Random.cc
If that does not work, try variations like:
g++ -o barn main.cc Pig.cc Random.cc Animal.cc Bird.cc Chicken.cc Cat.cc
The order should not matter. This is just the kind of thing I would try with a mystery-meat problem like this.
Yes this question has been asked before ... I've tried everything mentioned in the previous answers. My setup is really straightforward so this shouldn't be so hard.
I just want to program against mysql using C++. My source code is taken verbatem from the 'hello world' type example here:
http://dev.mysql.com/doc/refman/5.1/en/connector-cpp-examples-complete-example-1.html
I am on Ubuntu 12.10. I am trying:
g++ -Wall -o firsttry_prog -I/usr/include/mysqlcppconn -I/usr/local/boost_1_53_0 -L/usr/lib/x86_64-linux-gnu -l:libmysqlclient_r.so.18 -L/usr/lib/mysqlcppconn -lmysqlcppconn firsttry.cpp
It compiles (if I use -c option) but won't build, giving me the infamous:
/tmp/ccn768hj.o: In function `main':
firsttry.cpp:(.text+0x3a): undefined reference to `get_driver_instance'
A few details:
'firsttry.cpp' is just what I named the source code file, again taken verbatem from the official example
As you can see I AM linking in the mysqlclient library and the mysqlcppconn library. Many times when this question has been asked previously, the answer was to link those.
Some other historical answers suggest the sample source code is wrong and that the function in question needs to be in the sql::mysql namespace etc. I am pretty sure the source code is fine. Again, it compiles, and changing the namespaces in the source code just seems to make it worse.
Thank you in advance for any help you can provide.
So I have now had this problem for a week now and I became very frustrated with it as well. I just now was able to finally build a program that does nothing except login to mysql and I literally squealed with joy. Here is what I have and I hope it helps.
I first compiled the c++ connector library from source but after a while I thought maybe I did something wrong so I then just used apt to get it with:
sudo apt-get install libmysqlcppconn-dev
And here is my simple tester source file "tester.cpp"
#include <stdlib.h>
#include <iostream>
#include <mysql_connection.h>
#include <driver.h>
#include <exception.h>
#include <resultset.h>
#include <statement.h>
using namespace sql;
int main(void){
sql::Driver *driver;
sql::Connection *con;
driver = get_driver_instance();
con = driver->connect("tcp://127.0.0.1:3306","root","YOURPASSWORD");
return 0;
}
And finally g++ compile command:
g++ -Wall -I/usr/include/cppconn -o testapp tester.cpp -L/usr/lib -lmysqlcppconn
This worked for me and I hope it helps you solve your problem!
For me simply swapping the order of the last two arguments fixed this problem. I don't know why but the linker is able to find the function get_driver_instance if I specify the -lmysqlcppconn option at the end after the source file.
g++ -Wall -o firsttry_prog -I/usr/include/mysqlcppconn -L/usr/lib/mysqlcppconn firsttry.cpp -lmysqlcppconn
Also note that I took out the following options as I think they are redundant
-I/usr/local/boost_1_53_0 -L/usr/lib/x86_64-linux-gnu -l:libmysqlclient_r.so.18
In case you are as forgetful as me and didn't link the library in CMakeLists.txt:
target_link_libraries(<target> mysqlcppconn)
If all the paths are included throw param -I. You would see whether there is a problem if you compile like this:
g++ -g -o0 -I/usr/local/include -I/usr/local/boost/include -c main.cpp -o main.o
g++ -g -o0 -L/usr/local/lib -L/usr/local/mysql/lib -lmysqlcppconn main.o -o test
the problem will appear:
main.o: In function `main':
/home/huangxw/workspace/public/soal/test/main.cpp:165: undefined reference to `get_driver_instance'
collect2: ld returned 1 exit status
Now you must adjust the order of -lmysqlcppconn and main.o:
g++ -g -o0 -I/usr/local/include -I/usr/local/boost/include -c main.cpp -o main.o
g++ -g -o0 -L/usr/local/lib -L/usr/local/mysql/lib main.o -o test -lmysqlcppconn
That is all!!
The reason is simple. You can find out using the web or ask me to elaborate.
For one reason or another, I am messing around with the exit() function in c++. I am getting all kinds of strange errors from my mac running lion (64 bit). I am compiling using g++ -o -g -Wall.
Exhibit A:
#include <iostream>
int main(int arc, char *argv[]){
exit(1);
}
The Terminal output looks like this
$ g++ -o -g -Wall test main.cpp
ld: in test, can't link with a main executable for architecture x86_64
collect2: ld returned 1 exit status
but $ g++ -o test main.cpp compiles fine.
using #include<stdio.h> or #include<stdlib.h> result in the same compilation error.
I am just wondering if anyone might be able to see immediately what is going on here?
test is the name of the binary to produce, your first argument list should be:
> g++ -g -Wall -o test main.cpp
^^^^^^^ -o has test for an argument
-o is meant to be followed immediately by the name of the output file. It is probably trying to use your old binary 'test' as a source file, incorrectly.
Try this:
g++ -o test -g -Wall main.cpp
This question already has answers here:
What is an undefined reference/unresolved external symbol error and how do I fix it?
(39 answers)
Closed 7 years ago.
Following the example here: http://www.learncpp.com/cpp-tutorial/19-header-files/
Relating to add.h and main.cpp
When I try to compile main.cc (I just used another extension), I get the following:
/tmp/cckpbRW.o:main.cc:(.text+0x9d):undefined reference to 'add(int, int)' collect2: ld returned 1 exit status
How can I fix this issue?
Thanks.
Your didn't link your main object to your add one, so when the linker tries to build the executables it cannot find the definition of symbol add(int, int) it uses.
You should compile main object, add object and link them together, like this:
g++ -c -o main.o main.cpp
g++ -c -o add.o add.cpp
g++ -o executable main.o add.o
or
g++ -o executable main.cpp add.cpp
this will compile add.cpp and main.cpp together
Looks like you are not linking the second .cpp file into final executable. Either compile and link them at the same time:
$ c++ -Wall -Werror -pedantic -g -otest1 add.cpp main.cpp
or compile them separately and then link:
$ c++ -Wall -Werror -pedantic -g -c main.cpp
$ c++ -Wall -Werror -pedantic -g -c add.cpp
$ c++ -Wall -Werror -pedantic -g -otest1 add.o main.o