OpenGL Programming Guide: The Official Guide to Learning OpenGL, Version 4.3, Eighth Edition

Application-Generated Messages

There are two sources of message that are reserved for the application or its helper libraries and tools. These two sources are GL_DEBUG_SOURCE_APPLICATION, which is intended to be used by the application for its own messages, and GL_DEBUG_SOURCE_THIRD_PARTY, which is intended for use by third-party libraries such as middleware or by tools such as debuggers and profilers. Messages with these two source identifiers should never be generated by an OpenGL implementation. Instead they may be injected into the debug output stream by the application, library, or tool. To do this, call glDebugMessageInsert(), whose prototype is as follows:

void glDebugMessageInsert(GLenum source, GLenum type,                         GLuint ...