从自由线性对象接收的结构的生命周期是多少?

考虑:

#include "share/atspre_staload.hats"

%{^
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
%}
typedef statbuf = $extype "struct stat"
extern fun cstat: (string, &statbuf? >> statbuf) -> int = "mac#stat"
extern fun S_ISDIR: int -> bool = "mac#"
extern fun stat_mode: statbuf -> int = "mac#stat_mode"
%{
#define stat_mode(x) x.st_mode
%}

datavtype statbuf_vt = STAT of statbuf

fun stat(path: string): Option_vt(statbuf_vt) =
    let
        val buf = STAT(_)
        val STAT(hole) = buf
        val res = cstat(path, hole)
        prval _ = fold@(buf)
    in
        if res = 0 then Some_vt(buf)
        else
            let
                val ~STAT(_) = buf
            in
                None_vt()
            end
    end

implement main0() =
    let
        val path = "/etc/passwd"
        val- ~Some_vt(~STAT(buf)) = stat(path)
    in
        println!(~S_ISDIR(stat_mode(buf)))
    end

buf 最后?它似乎不需要被释放——瓦尔格林看到3个alloc和3个free,没有问题。但不是吗 缓冲器 由它管理的部分内存 STAT 线性物体?