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red zone

On Linux and macOS PCs, 128 bytes just below the stack pointer that a function may use without moving the stack pointer; Windows has no such area.

The x86-64 ABI used by Linux and macOS guarantees the 128 bytes below rsp are not overwritten asynchronously, so leaf functions may use them as scratch; 64-bit Windows and ARM64 Linux have no red zone, while Apple's ARM64 ABI also allows 128 bytes.

Examples

  • A Linux or macOS x86-64 leaf function may use the 128 bytes below rsp without moving rsp. Windows has no red zone.

See also

leaf function ABI stack pointer
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