   problem with geometry shaders
  himy geomtry shader dosent work in core 150. my OpenGL version is 3.3vertex shader code#version 150 corein vec3 in_Position;uniform mat4 in_ModelViewMatrix;in vec4 in_VertexColor;out vec4 VertexColor;void main(void){VertexColor = in_VertexColor;gl_Position = in_ModelViewMatrix * vec4(in_Position,1.0);}geomtery shader:#version 150#extension GL_EXT_geometry_shader4 : enablevoid main(void){//increment variableint i;//Pass-thru!for(i=0; i< gl_VerticesIn; i++){gl_Position = gl_PositionIn;EmitVertex();}EndPrimitive();}fragment shader:#version 150 corein vec4 VertexColor;out vec4 out_Color;void main(void){   out_Color = vec4(0);}and any thing doesn't show in screen,but it compile successfully what is wrong?   