SDL: atomic: Use __atomic_signal_fence() for SDL_CompilerBarrier()

SDL Commits
1 
From d5acd7f123f593a256124f313a47816c97532652 Mon Sep 17 00:00:00 2001
From: Cameron Gutman <[EMAIL REDACTED]>
Date: Sun, 26 Apr 2026 21:42:23 -0500
Subject: [PATCH] atomic: Use __atomic_signal_fence() for SDL_CompilerBarrier()

This is the (slightly) more standard way to accomplish it.
---
 include/SDL3/SDL_atomic.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/SDL3/SDL_atomic.h b/include/SDL3/SDL_atomic.h
index e14a02a8ceb9b..b6094b2550519 100644
--- a/include/SDL3/SDL_atomic.h
+++ b/include/SDL3/SDL_atomic.h
@@ -156,6 +156,8 @@ extern SDL_DECLSPEC void SDLCALL SDL_UnlockSpinlock(SDL_SpinLock *lock);
  */
 #define SDL_CompilerBarrier() DoCompilerSpecificReadWriteBarrier()
 
+#elif SDL_HAS_BUILTIN(__atomic_signal_fence) || (defined(__GNUC__) && (__GNUC__ >= 5))
+#define SDL_CompilerBarrier()   __atomic_signal_fence(__ATOMIC_SEQ_CST)
 #elif defined(_MSC_VER) && (_MSC_VER > 1200) && !defined(__clang__)
 void _ReadWriteBarrier(void);
 #pragma intrinsic(_ReadWriteBarrier)