glAttachShader

glAttachShader: man3/glAttachShader.xml

In order to create a complete shader program, there must be a way to specify the list of things that will be linked together. Program objects provide this mechanism. Shaders that are to be linked together in a program object must first be attached to that program object. glAttachShader attaches the shader object specified by shader to the program object specified by program. This indicates that shader will be included in link operations that will be performed on program. All operations that can be performed on a shader object are valid whether or not the shader object is attached to a program object. It is permissible to attach a shader object to a program object before source code has been loaded into the shader object or before the shader object has been compiled. It is permissible to attach multiple shader objects of the same type because each may contain a portion of the complete shader. It is also permissible to attach a shader object to more than one program object. If a shader object is deleted while it is attached to a program object, it will be flagged for deletion, and deletion will not occur until glDetachShader is called to detach it from all program objects to which it is attached.