Go version

go version devel go1.24-bea9b91f0f Tue Nov 5 01:16:03 2024 +0000 windows/amd64

What did you do?

Run go build -gcflags=-m .

package main

import (
	"syscall"
	"unsafe"
)

var sink byte
var procProcessPrng = syscall.NewLazyDLL("bcryptprimitives.dll").NewProc("ProcessPrng").Addr()

func main() {
	var buf [10]byte
	syscall.SyscallN(procProcessPrng, uintptr(unsafe.Pointer(&buf[0])), uintptr(len(buf)))
	sink ^= buf[0]
}

What did you see happen?

The syscall.SyscallN variadic argument escaped to the heap.

./main.go:13:18: ... argument escapes to heap

What did you expect to see?

The syscall.SyscallN variadic argument didn't escape to the heap, just as other syscall.SyscalX functions.

./main.go:13:18: ... argument does not escape

Note that syscall.SyscallN is implemented by runtime.syscall_syscalln, which makes sure that the variadic argument doesn't escape:

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