-# define CL_CONTEXT_SHOW_DIAGNOSTICS_INTEL 0x4106
-# define CL_CONTEXT_DIAGNOSTICS_LEVEL_GOOD_INTEL 0x1
-# define CL_CONTEXT_DIAGNOSTICS_LEVEL_BAD_INTEL 0x2
-# define CL_CONTEXT_DIAGNOSTICS_LEVEL_NEUTRAL_INTEL 0x4
+# ifndef CL_CONTEXT_SHOW_DIAGNOSTICS_INTEL
+# define CL_CONTEXT_SHOW_DIAGNOSTICS_INTEL 0x4106
+# endif
+# ifndef CL_CONTEXT_DIAGNOSTICS_LEVEL_GOOD_INTEL
+# define CL_CONTEXT_DIAGNOSTICS_LEVEL_GOOD_INTEL 0x1
+# endif
+# ifndef CL_CONTEXT_DIAGNOSTICS_LEVEL_BAD_INTEL
+# define CL_CONTEXT_DIAGNOSTICS_LEVEL_BAD_INTEL 0x2
+# endif
+# ifndef CL_CONTEXT_DIAGNOSTICS_LEVEL_NEUTRAL_INTEL
+# define CL_CONTEXT_DIAGNOSTICS_LEVEL_NEUTRAL_INTEL 0x4
+# endif