Clarify that omitting nostack is a promise from the compiler to the programmer
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rustbot
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jyn514
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Sep 16, 2025
| r[asm.options.supported-options.nostack] | ||
| - `nostack`: The assembly code does not push data to the stack, or write to the stack red-zone (if supported by the target). | ||
| If this option is *not* used then the stack pointer is guaranteed to be suitably aligned (according to the target ABI) for a function call. | ||
| If this option is *not* used then the stack pointer is guaranteed by the compiler to be suitably aligned (according to the target ABI) for a function call at the start of the assembly code. |
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at the start of the assembly code
this makes me feel weird — i suspect that inline asm isn't allowed to modify the stack pointer at all? but i'm not sure if that's true, i don't want to write it in the reference without more background info.
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There's already a requirement that the stack pointer must be restored to its original value before returning from an asm block. This applies regardless of whether nostack is used.
Amanieu
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Sep 16, 2025
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cc @Amanieu