[cairo] About cairo memory leak

[唐博]

Hi, Mr Bosmans . There's a problem puzzle me for a long time. I explant cairolib but has memory leak.
 When I use  cairo_set_source_rgb(cr, 0.1, 0.2, 0.3) , it's OK. If  I use variable(double) as the cairo_set_source_rgb  param 
and when the program is running the variable isvariational. It will memory leak. I use hooklogger to check, it says _pixman_image_allocate(),
 but I didn't modify it.Wait your reply , thank you very very much.
                                                                                                                                                              by tang, China.