(This is the documentation for SDL3, which is the current stable version. SDL2 was the previous version!)

SDL_MemoryBarrierRelease

Insert a memory release barrier (macro version).

Header File

Syntax

#define SDL_MemoryBarrierRelease() SDL_MemoryBarrierReleaseFunction()

Remarks

Memory barriers are designed to prevent reads and writes from being reordered by the compiler and being seen out of order on multi-core CPUs.

A typical pattern would be for thread A to write some data and a flag, and for thread B to read the flag and get the data. In this case you would insert a release barrier between writing the data and the flag, guaranteeing that the data write completes no later than the flag is written, and you would insert an acquire barrier between reading the flag and reading the data, to ensure that all the reads associated with the flag have completed.

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.

For more information on these semantics, take a look at the blog post: http://preshing.com/20120913/acquire-and-release-semantics

This is the macro version of this functionality; if possible, SDL will use compiler intrinsics or inline assembly, 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.

Thread Safety

Obviously this macro is safe to use from any thread at any time, but if you find yourself needing this, you are probably dealing with some very sensitive code; be careful!

Version

This macro is available since SDL 3.1.3.