popen-锁定还是线程安全? [英] popen - locks or not thread safe?

问题描述

我已经看到了popen()/pclose()的一些实现.他们都使用了静态的pid列表，并且没有锁定:

I've seen a few implementations of popen()/pclose(). They all used a static list of pids, and no locking:

static int *pids;
static int fds;

if (!pids) {
        if ((fds = getdtablesize()) <= 0)
            return (NULL);
        if ((pids = malloc(fds * sizeof(int))) == NULL)
            return (NULL);
        memset(pids, 0, fds * sizeof(int));
    }

或者说是NetBSD:

Or this, supposedly NetBSD:

static struct pid {
    struct pid *next;
    FILE *fp;
    pid_t pid;
} *pidlist; 

    /* Link into list of file descriptors. */
    cur->fp = iop;
    cur->pid =  pid;
    cur->next = pidlist;
    pidlist = cur;

它是什么样子-不是线程安全的实现?还是我缺少明显的东西?

Is it what it looks like - a not thread safe implementation? Or am I missing something obvious?

推荐答案

The GNU libc implementation is threadsafe if libc is configured to be reentrant (which it is likely to be). However, this may not be the case for other implementations of libc.

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