Discovered pro tip of my life :
Never trust your code

Achievements unlocked :
Successfully running C++ GPU accelerated offscreen rendering engine with texture loading code having faulty validation bug over a year on production for more than 1.5M daily Android active users without any issues.

History : Recently I was writing a new rendering engineering that uses our GPU pipeline engine.. and our prototype android app benchmark test always fails with black rendering frame detection assertion.

Practice:
Spend more than a month to debug a GPU pipeline system based on directed acyclic graph based rendering algorithm.

New abilities added :
Able to debug OpenGL ES code on Android using print statement placed in source code using binary search.

But why?
I was aware of the issue over a month and just ignored it thinking it's a driver bug in my android device.. but when the api was used by one of Android dev, he reported the same issue. In the same day at night 2:59AM ....

Satan came to me and told me that " ok listen man, here is what I am gonna do with you today, your new code will be going production in a week, and the renderer will give you just one black frame after random time, and after today 3AM, your code will not show GL Errors if you debug or trace. Buhahahaha ahhaha haahha..... Puffff"

And he was gone..
Thanks satan for not killing me.. I will not trust stable production code anymore enevn though every line is documented and peer reviewed.