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From: goer@sophist.uucp (Richard Goerwitz)
Newsgroups: gnu.bash.bug
Subject: question about nojobs.c, bash-1.04
Message-ID: <7551@tank.uchicago.edu>
Date: 9 Feb 90 18:37:47 GMT
Sender: news@tank.uchicago.edu
Reply-To: goer@sophist.UUCP (Richard Goerwitz)
Organization: University of Chicago
Lines: 54

Silly question?

/* from jobs.h */

union wait {
  struct {                           /* clever way of getting at
    unsigned char low;                * wait's high and low 
    unsigned char high;               * status bytes
  }                                   * /
  bytes;
  short word;
};

#define WSTOPPED 0177
#define w_status word
#define w_termsig bytes.low & 0x7f    /* mask out eighth bit */
#define w_stopsig bytes.high
#define w_retcode bytes.high


/* from nojobs.c, line 163 and following: */

  while ((got_pid = wait (&status)) != pid)
    {
      if (got_pid < 0 && errno == ECHILD)
	{
	  status.w_termsig = status.w_retcode = 0;    /* <-- NOTE */
	  break;
	}
      else if (got_pid < 0 && errno != EINTR)
	programming_error ("got errno %d while waiting for %d", errno, pid);
    }


The hitch here is that w_termsig expands to bytes.low & 0x7f.  Hence the
entire expression expands to

       status.bytes.low & 0x7f = status.w_retcode = 0;

What is the intention here?  I'm just curious.  If the attempt is being
made to zero out the lower seven bits of status.bytes.low, wouldn't

       status.bytes.low &= 0x80;

be more appropriate?

I don't claim to be a wizard.  I'm just trying to compile Bash on my
Xenix box.

If this is a silly question, and I should have seen what was going on
I'd still like to know about my mistake.

   -Richard L. Goerwitz              goer%sophist@uchicago.bitnet
   goer@sophist.uchicago.edu         rutgers!oddjob!gide!sophist!goer