Provided by: libsdl3-doc_3.2.8+ds-1_all 

NAME
SDL_Semaphore - A means to manage access to a resource, by count, between threads.
HEADER FILE
Defined in SDL3/SDL_mutex.h
SYNOPSIS
#include "SDL3/SDL.h" typedef struct SDL_Semaphore SDL_Semaphore;
DESCRIPTION
Semaphores (specifically, "counting semaphores"), let X number of threads request access at the same time, each thread granted access decrementing a counter. When the counter reaches zero, future requests block until a prior thread releases their request, incrementing the counter again. Wikipedia has a thorough explanation of the concept: https://en.wikipedia.org/wiki/Semaphore_(programming)
AVAILABILITY
This struct is available since SDL 3.2.0. Simple Directmedia Layer SDL 3.2.8 SDL_Semaphore(3type)