MPMC Lock-Free Bounded Queue

This is a multi-producer, multi-consumer (MPMC) lock-free queue implemented as a bounded ring/circular buffer. The queue size is fixed at creation to allow full control over memory allocation and enable natural backpressure.

Features

• Bounded capacity for predictable memory usage.
• Designed for high performance and low latency.
• False sharing avoidance via cache line (64-byte) aligned structure members.
• Portable across MSVC, GCC, and Clang compilers.
• Can be used with C99 or later.

Implementation details

• Uses C11 atomics when available for optimal atomic operations and explicit memory ordering.
• On MSVC with C99, falls back to Windows Interlocked* API calls, which always use memory_order_seq_cst semantics.
• On MSVC with C11, uses the C11 <stdatomic.h> atomics for explicit memory ordering.
• On GCC and Clang with C11 enabled, uses C11 atomics (<stdatomic.h>) for explicit memory ordering.
• On GCC 4.7+ and Clang 3.3.3+ without C11, uses the GCC/Clang __atomic* built-ins with explicit memory ordering.
• On older GCC and Clang versions, or without C11, uses the older __sync* built-ins, which always use memory_order_seq_cst semantics.

Platform / Compiler support summary

Platform	Compiler Version	C Standard	Atomic API	Memory Ordering Support
MSVC	≤ 2022 17.5	C99	Interlocked*	Only memory_order_seq_cst
MSVC	≥ 2022 17.5	C11	C11 atomics	Explicit
GCC	≥ 4.7	C11	C11 atomics	Explicit
GCC	≥ 4.7	C99	__atomic*	Explicit
GCC	< 4.7	C99	__sync*	Only memory_order_seq_cst
Clang	≥ 3.3.3	C11	C11 atomics	Explicit
Clang	≥ 3.3.3	C99	__atomic*	Explicit
Clang	< 3.3.3	C99	__sync*	Only memory_order_seq_cst