"extern" problem

[yygyt]

On Ubuntu, I am trying to compile a GL project consisting of 3 source files. One of them which has the main function in it has this code section

extern void gfxInit();
extern GLfloat CylVertexArray[];
extern GLubyte CylFaceArray[];
extern int CylNofFaceVertex[];

When compiling with this command
"gcc cyl.cpp -lglut -lGLU -lGL -o cyl"

I get these errors:

/tmp/ccTmVLQZ.o: In function `main':
cyl.cpp:(.text+0x7d): undefined reference to `gfxInit()'
/tmp/ccTmVLQZ.o: In function `displayFunc()':
cyl.cpp:(.text+0xb6): undefined reference to `CylVertexArray'
cyl.cpp:(.text+0xf2): undefined reference to `CylFaceArray'
cyl.cpp:(.text+0xfc): undefined reference to `CylNofFaceVertex'
cyl.cpp:(.text+0x122): undefined reference to `CylNofFaceVertex'
collect2: ld returned 1 exit status

I really do not know what -lglut,-lGL and that stuff mean, but I thought that i got these errors because of the wrong usage of extern function.
Any suggestions?

Thanks in advance

[jsmith]

The things you refer to are the OpenGL libraries.

Your problem is that if you have 3 source (.cpp) files, you need to compile and link all of them,
not just cyl.cpp.

So

g++ file1.cpp file2.cpp file3.cpp -lglut -lGLU -lGL -o cyl

[yygyt]

I knew it was a linking issue. I just didn't find how to link these files. Thanks a lot. It is solved now.