The reason for using builtin atomic is that in C++, when include <atomic> in <nuttx/atomic.h> easily conflicts with third-party function libraries. We wanted to completely separate the implementation of <nuttx/atomic.h>.
There are two points:
1. use builtin function directly.
2. Without the standard library implementation, need implement "atomic_fetch_xxx", leading conflicts with the standard library used by third-party programs, introducing redefinition issues and requiring name changes.
Signed-off-by: zhangyu117 <zhangyu117@xiaomi.com>
Split the atomic implementation into three files:
- arch_atomic.h: Shared macros (STORE, LOAD, etc.) using atomic_lock()/
atomic_unlock() abstraction
- arch_atomic_irq.c: 32-bit atomic functions using IRQ disable (conditional
on CONFIG_LIBC_ATOMIC_IRQ via Make.defs)
- arch_atomic64.c: 64-bit atomic functions using spinlock (always compiled,
multi-core safe). The __atomic_* functions are always provided (GCC
runtime helpers), while nx_atomic_* functions are conditional on
!CONFIG_LIBC_ATOMIC_TOOLCHAIN.
Signed-off-by: zhangyu117 <zhangyu117@xiaomi.com>
