Many SDL games work by polling (ie reading all the time) the event queue.

https://wiki.libsdl.org/SDL_PollEvent

The example code shows the ugly. while(1) { SDL_PollEvent(...); }

It kills any CPU class.

Better main loop would be with SDL_WaitEvent/SDL_WaitEventTimeout

https://wiki.libsdl.org/SDL_WaitEvent
https://wiki.libsdl.org/SDL_WaitEventTimeout

At least, those calls shouldn't eat all the CPU.

A quick search with G**gle on GitHub :

SDL_PollEvent site:github.com -> about 9500 results
SDL_WaitEvent site:github.com -> about 2200 results
SDL_WaitEventTimeout site:github.com -> about 300 results

See the disaster. :)