glDebugMessageCallback

glDebugMessageCallback: man4/glDebugMessageCallback.xml

glDebugMessageCallback sets the current debug output callback function to the function whose address is given in callback. The callback function should have the following prototype (in C), or be otherwise compatible with such a prototype:

typedef void (APIENTRY *DEBUGPROC)(GLenum source,
        GLenum type,
        GLuint id,
        GLenum severity,
        GLsizei length,
        const GLchar *message,
        void *userParam);

This function is defined to have the same calling convention as the GL API functions. In most cases this is defined as APIENTRY, although it will vary depending on platform, language and compiler. Each time a debug message is generated the debug callback function will be invoked with source, type, id, and severity associated with the message, and length set to the length of debug message whose character string is in the array pointed to by message userParam will be set to the value passed in the userParam parameter to the most recent call to glDebugMessageCallback.

When the GL is in use remotely, the server may not be able to call functions in the client's address space. In such cases, the callback function may not be invoked and the user should retrieve debug messages from the context's debug message log by calling glGetDebugMessageLog.