In the manual under "ent_getvertex"
In the last example, it mentions the following:
CONTACT* contact = ent_getvertex(you,NULL,vertex_num);
c.z += 10; // increase the vertex height
c.v = NULL; // c.x,y,z was changed, instead of c.v
ent_setvertex(you,c,vertex_num); // update the mesh
If I am not mistaken, shouldn't it be "CONTACT* c = ent_getvertex(you,NULL,vertex_num);"