Slight tweak to the the error function from http://t-machine.org/index.php/2013/10/12/opengl-es-2-for-ios-gldebugging-and-cleaning-up-our-vbos-vaos-and-draw-calls/

GLK2Error.m

#include <stdio.h>
#include "GLK2GetError.h"
#include <GLKit/GLKit.h>

void _gl2CheckAndClearAllErrorsImpl(char *source_function, char *source_file, int source_line)
{
  GLenum glErrorLast;
  while( (glErrorLast = glGetError()) != GL_NO_ERROR ) // GL spec says you must do this in a WHILE loop
	{
		/** OpenGL spec defines only 6 legal errors, that HAVE to be re-used by all gl method calls. OH THE PAIN! */
		NSDictionary* glErrorNames = @{ @(GL_INVALID_ENUM) : @"GL_INVALID_ENUM", @(GL_INVALID_VALUE) : @"GL_INVALID_VALUE", @(GL_INVALID_OPERATION) : @"GL_INVALID_OPERATION", @(GL_STACK_OVERFLOW) : @"GL_STACK_OVERFLOW", @(GL_STACK_UNDERFLOW) : @"GL_STACK_UNDERFLOW", @(GL_OUT_OF_MEMORY) : @"GL_OUT_OF_MEMORY" };

		NSLog(@"GL Error: %@ in %s @ %s:%d", [glErrorNames objectForKey:@(glErrorLast)], source_function, source_file, source_line );

		NSCAssert( FALSE, @"OpenGL Error; you need to investigate this!" ); // can't use NSAssert, because we're inside a C function
	}
}

#define gl2CheckAndClearAllErrors() _gl2CheckAndClearAllErrorsImpl(__PRETTY_FUNCTION__,__FILE__,__LINE__)

The idea is that you use the macro gl2CheckAndClearAllErrors() rather than the direct method call.

Allows you to pass through the function, file and line from the call site.