SDL_MemoryBarrierRelease(3)

💅 SDL_MemoryBarrierRelease 💅

okay bestie, welcome to the SDL3 FUNCTIONS section of the manual — this one's called SDL_MemoryBarrierRelease(3) and it's a whole little macro that does very important things to your CPU's brain. 🧠✨

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✨ NAME ✨

SDL_MemoryBarrierRelease — drop in a memory release barrier (the macro version, bestie 💖).

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🎀 SYNOPSIS 🎀

#include <SDL3/SDL_atomic.h>

#define SDL_MemoryBarrierRelease() SDL_MemoryBarrierReleaseFunction()

that's it. that's the whole vibe. a macro that literally just expands to a function call. iconic honestly. 👑

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🌸 DESCRIPTION 🌸

okay so. memory barriers exist to stop reads and writes from getting reordered by the compiler, and to stop them from being seen out of order on multi-core CPUs. no cap, that's the whole job. 🦋

a typical pattern would be: thread A writes some data and a flag, and thread B reads the flag and gets the data. in that case you'd insert a release barrier between writing the data and writing the flag — which guarantees the data write completes no later than the flag gets written. then you'd insert an acquire barrier between reading the flag and reading the data, to make sure all the reads associated with the flag have completed. it's giving choreography. it's giving synchronized swimming. 🏊♀️✨

in this pattern you should always see a release barrier paired with an acquire barrier, and you should gate the data reads/writes with a single flag variable. one flag. that's the rule. periodt. 💅

if you want more info on these semantics, go read this blog post, it's a classic fr fr:

http://preshing.com/20120913/acquire-and-release-semantics

now the important part: this is the macro version of this functionality. if possible, SDL will use compiler intrinsics or inline assembly (fancy 💖), but some platforms might need to call the function version of this — SDL_MemoryBarrierReleaseFunction — to do the heavy lifting. apps that can use the macro should favor it over the function. macro girlies stay winning. 🌈

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😭 THREAD SAFETY 😭

obviously this macro is safe to use from any thread at any time, no notes. but — if you find yourself needing this, you are probably dealing with some very sensitive code, so be careful! like, careful careful. 👀🚨

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⭐ AVAILABILITY ⭐

this macro is available since SDL 3.2.0. if you're on anything older, it's simply not the moment for you, bestie. 🫶

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💜 SEE ALSO 💜

• SDL_MemoryBarrierAcquire(3) — the other half of the duo, the acquire to this release 🧚
• SDL_MemoryBarrierReleaseFunction(3) — the function that this macro calls when the platform can't do the intrinsic thing 🔥

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lowkey a whole lot of responsibility for one little macro but she handles it. be careful out there, and pair your barriers. always. 💖

later bestie!! this page came from Simple Directmedia Layer, version SDL 3.4.18, and it's the SDL_MemoryBarrierRelease(3) page, mwah 💋✨