Don't re-read the hints when opening the game controller. Instead use SDL_GameControllerAddMapping() to add hints after initialization.

include/SDL_hints.h

@@ -209,6 +209,9 @@ extern "C" {
  *  \brief  A variable that lets you manually hint extra gamecontroller db entries
  *
  *  The variable expected newline delimited rows of gamecontroller config data, see SDL_gamecontroller.h
+ *
+ *  This hint must be set before calling SDL_Init(SDL_INIT_GAMECONTROLLER)
+ *  You can update hints after the system is initialized with SDL_GameControllerAddMapping()
  */
 #define SDL_HINT_GAMECONTROLLERCONFIG "SDL_GAMECONTROLLERCONFIG"
 

src/joystick/SDL_gamecontroller.c

@@ -879,8 +879,6 @@ SDL_GameControllerOpen(int device_index)
     }
 
 	// Find a controller mapping 
-    // Check for hints in case someone has changed them recently
-    SDL_GameControllerLoadHints();
 	pSupportedController =  SDL_PrivateGetControllerMapping(device_index);
 	if ( !pSupportedController ) {
 		SDL_SetError("Couldn't find mapping for device (%d)", device_index );