[ODE] Newbie compilation problems

[Jan Ekholm]

Hi,

I installed 0.039 from a package for "Debian unstable". It contains
libode.a and the header files and not much else.

Anyway, I can't seem to get even a trivial application compiled using
either the normal C interface nor the C++ interface that some test apps
seem to use (but which does not seem to be documented?).

What I try to compile is:

#include <stdlib.h>
extern "C" {
#include <ode/ode.h>
}

int main (int argc, char * argv[]) {
    // create the ODE world
    dWorldID world = dWorldCreate();
    // set standard gravity
    dWorldSetGravity ( world, 0, 0, -9.81 );

    // here would be dragons

    // we're done
    dWorldDestroy ( world );
    dCloseODE();

    // go away
    exit ( EXIT_SUCCESS );
}

The error I get is:

g++ -g -Wall   /usr/lib/libode.a  odetest1.cpp   -o odetest1
/tmp/ccQewNLY.o(.text+0x11): In function `main':
/home/chakie/prog/c++/ode/odetest1.cpp:11: undefined reference to
`dWorldCreate'
/tmp/ccQewNLY.o(.text+0x43):/home/chakie/prog/c++/ode/odetest1.cpp:14:
undefined reference to `dWorldSetGravity'
/tmp/ccQewNLY.o(.text+0x51):/home/chakie/prog/c++/ode/odetest1.cpp:19:
undefined reference to `dWorldDestroy'
/tmp/ccQewNLY.o(.text+0x59):/home/chakie/prog/c++/ode/odetest1.cpp:20:
undefined reference to `dCloseODE'
collect2: ld returned 1 exit status
make: *** [odetest1] Error 1

I've tried with both gcc and g++, with having the ode.h marked as
extern "C" and without. The static library /usr/lib/libode.a does seem to
contain the needed symbols. The only thing I can think of is that libode.a
has been compiled with some other compiler. So I tested to compile my app
with g++ versions 3.3, 3.2 and 2.95. No help, so apparently I do something
really stupid here. I hope it's nothing I have to be too ashamed about.

Another sample using the C++ interface:


#include <stdlib.h>

extern "C" {
#include <ode/ode.h>
}

static dWorld world;

int main (int argc, char * argv[]) {
    // set standard gravity
    world.setGravity ( 0, 0, -9.81 );

    exit ( EXIT_SUCCESS );
}


Give me this:

g++ -g -Wall   /usr/lib/libode.a  odetest1.cpp   -o odetest1
/tmp/ccouzuZN.o(.gnu.linkonce.t._ZN6dWorldC1Ev+0xb): In function
`dWorld::dWorld[in-charge]()':
/usr/include/ode/odecpp.h:42: undefined reference to `dWorldCreate'
/tmp/ccouzuZN.o(.gnu.linkonce.t._ZN6dWorld10setGravityEddd+0x45): In
function `dWorld::setGravity(double, double, double)':
/home/chakie/prog/c++/ode/odetest1.cpp:24: undefined reference to `dWorldSetGravity'
/tmp/ccouzuZN.o(.gnu.linkonce.t._ZN6dWorldD1Ev+0xf): In function
`dWorld::~dWorld [in-charge]()':
/usr/include/ode/odecpp.h:42: undefined reference to `dWorldDestroy'
collect2: ld returned 1 exit status
make: *** [odetest1] Error 1

One error that caught my interest was:

    /usr/include/ode/odecpp.h:42: undefined reference to `dWorldCreate'

    33 class dWorld {
  ...
    40 public:
    41   dWorld()
    42     { _id = dWorldCreate(); }

Is there some problem with missing extern "C" or something similar here,
as all the includes from ode.h should have defined dWorldCreate() long
before odecpp.h got included.

The ODE docs are excellent, btw. They are fun reading although I have a
firm dislike for all things math and physics. :)

Regards,
    Jan Ekholm

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