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Date: Thu, 17 Feb 2011 21:23:01 -0800
Message-ID: <AANLkTi=MJ6Ze9GHQeAfnvO-UE9aNEUfYLCnBdZv5H+bL@mail.gmail.com>
From: ron minnich <rminnich@gmail.com>
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
Content-Type: text/plain; charset=ISO-8859-1
Subject: Re: [9fans] Modern development language for Plan 9,
 WAS: Re: RESOLVED: recoving important header file rudely
Topicbox-Message-UUID: b0102252-ead6-11e9-9d60-3106f5b1d025

I was looking at another fine example of modern programming from glibc
and just had to share it.

Where does the getpid happen? It's anyone's guess. This is just so
readable too ... I'm glad they want to such effort to optimize getpid.

ron

#ifndef NOT_IN_libc
static inline __attribute__((always_inline)) pid_t really_getpid (pid_t oldval);

static inline __attribute__((always_inline)) pid_t
really_getpid (pid_t oldval)
{
  if (__builtin_expect (oldval == 0, 1))
    {
      pid_t selftid = THREAD_GETMEM (THREAD_SELF, tid);
      if (__builtin_expect (selftid != 0, 1))
	return selftid;
    }

  INTERNAL_SYSCALL_DECL (err);
  pid_t result = INTERNAL_SYSCALL (getpid, err, 0);

  /* We do not set the PID field in the TID here since we might be
     called from a signal handler while the thread executes fork.  */
  if (oldval == 0)
    THREAD_SETMEM (THREAD_SELF, tid, result);
  return result;
}
#endif

pid_t
__getpid (void)
{
#ifdef NOT_IN_libc
  INTERNAL_SYSCALL_DECL (err);
  pid_t result = INTERNAL_SYSCALL (getpid, err, 0);
#else
  pid_t result = THREAD_GETMEM (THREAD_SELF, pid);
  if (__builtin_expect (result <= 0, 0))
    result = really_getpid (result);
#endif
  return result;
}

libc_hidden_def (__getpid)
weak_alias (__getpid, getpid)
libc_hidden_def (getpid)