Question

When compiling the following C code with ndk-build in Terminal (I’m running Ubuntu):

#include <jni.h>

#include <GLES/gl.h>
#include <GLES/glext.h>

#include "org_opengldrawinjni_DrawinJNI.h"


JNIEXPORT void JNICALL Java_org_opengldrawinjni_DrawinJNI_Draw
  (JNIEnv *envptr, jobject jobj)
{
 GLfloat vertices[] =
  { 1.0, 0.0, 0.0,
    1.0, 1.0, 0.0,
    0.0, 0.0, 0.0
  };
 GLubyte indices[] = { 0, 1, 2 };
 glVertexPointer(3, GL_FLOAT, 0, vertices);
 glDrawElements(GL_TRIANGLES, 3, GL_UNSIGNED_BYTE, indices);
}

with this Android.mk file:

   LOCAL_PATH := $(call my-dir)

   include $(CLEAR_VARS)

   LOCAL_MODULE    := OpenGLJNI
   LOCAL_SRC_FILES := org_opengldrawinjni_DrawinJNI.c
   LOCAL_LDLIBS := -llog -lGLESv1_CM.so

   include $(BUILD_SHARED_LIBRARY)

I get an error, undefined reference to glVertexPointer. I’m wondering why because I believe I properly included the headers and linked up the libraries in the Android.mk

/home/thomas/Documents/LinuxProgramming/EclipseWorkspace/OpenGLDrawinginJNI/obj/local/armeabi/objs/OpenGLJNI/org_opengldrawinjni_DrawinJNI.o: In function `Java_org_opengldrawinjni_DrawinJNI_Draw':
/home/thomas/Documents/LinuxProgramming/EclipseWorkspace/OpenGLDrawinginJNI/jni/org_opengldrawinjni_DrawinJNI.c:33: undefined reference to `glVertexPointer'
collect2: ld returned 1 exit status
make: *** [/home/thomas/Documents/LinuxProgramming/EclipseWorkspace/OpenGLDrawinginJNI/obj/local/armeabi/libOpenGLJNI.so] Error 1

Thanks!

Answer 1

I can’t think of anything wrong but when I checked my make file there is one difference.
Since I’m not good with compilers I don’t know if it is relevant:

LOCAL_LDLIBS := -lGLESv1_CM -ldl -llog

Dynamic Linker Library:

is available and can be used
to use the dlopen()/dlsym()/dlclose()
functions provided by the Android
dynamic linker. You will need to link
against /system/lib/libdl.so with:

LOCAL_LDLIBS := -ldl

Hope it helps