Undefined reference to scene_render - c++

Question

Here is the following main function or my program
void scene_render(const struct Scene *s);
int main(void) { //leave main as is
struct Scene myScene;
scene_init(&myScene);
int keep_going = 1;
while (keep_going == 1) {
cons_clear_screen(); //clear off-screen display buffer
scene_render(&myScene); //render the scene to display buffer
cons_update(); //copy the display buffer to the display
cons_sleep_ms(ANIMATION_DELAY); //pause
scene_update(&myScene); //update the scene
int key = cons_get_keypress(); //see if the user has pressed a key
if (key != -1) {
keep_going = 0;
}
}
return 0;
}
void scene_render(Scene *s)
{
cons_clear_screen();
for(int i=0; i<NUM_PARTICLES; i++)
{
particle_render(&s->parts[i]);
}
}
When I run the makefile command on Cygwin, it passes the errors and starts compiling, but hits an error when it hits scene_render(&myScene);. It says that a reference to it is undefined. It refers to a variable in a function that is a const struct, while all other instances where &myScene is called are merely structs. Any idea what the issue may be? This lab is mostly about using pointers, if that helps.
The program (with assistance from external functions) should generate and throw randomly colored pixels around the command window, bouncing them back to keep them in the screen. Deleting the issue causes the program to compile successfully, but then loads a blank window that seems to do nothing.

Answer 1

Problem
With
void scene_render(const struct Scene *s);
you promise scene_render takes a const struct Scene as a parameter. By the way, you can discard the use of struct here. C++ knows Scene is a struct.
But the function that is defined is
void scene_render(Scene *s)
which takes a plain old, non-const Scene, so when the linker goes looking for a function that matches the promise it does not find one.
Solution
Change
void scene_render(Scene *s)
to
void scene_render(const Scene *s)
to keep the promise. But make certain that const-correctness is maintained throughout.