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Clarify that omitting nostack is a promise from the compiler to the programmer #1999

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Clarify that omitting nostack is a promise from the compiler to the programmer #1999

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2 changes: 1 addition & 1 deletion src/inline-assembly.md
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Expand Up @@ -1184,7 +1184,7 @@ let _: () = unsafe {

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.


<!-- no_run: Test has undefined behavior at runtime -->
```rust,no_run
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