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From: lm@slovax.Eng.Sun.COM (Larry McVoy)
Newsgroups: comp.lang.perl
Subject: perl & vfork on sparc machines
Message-ID: <549@appserv.Eng.Sun.COM>
Date: 19 Apr 91 18:01:50 GMT
Sender: news@appserv.Eng.Sun.COM
Reply-To: lm@sun.UUCP (Larry McVoy)
Organization: Sun Microsystems, Mountain View
Lines: 20

I was porting perl to an alpha copy of our next release of the OS and ran
into the following problem.  It is unlikely that you will see this, but
just in case...

In util.c, function mypopen(), there is a line like so:

	while ((pid = (doexec?vfork():fork())) < 0)

The problem showed up when I compiled w/ the optimizer turned on.  The bug
is that the internal release did not have a copy of vfork.h which has a
pragma that tells the compiler not to optimize around vfork()s (a vfork
is quite similar to a longjmp and both have a nasty interactions with 
register allocations).  The arg "mode" was in a register and it got
stomped on by the child.

The only reason I mention it is that you may run into the problem on
some other risc that doesn't have vfork.h or calls it something else.
Pretty unlikely, but you never know.
---
Larry McVoy, Sun Microsystems     (415) 336-7627       ...!sun!lm or lm@sun.com