Xref: utzoo comp.std.c:1088 comp.sys.encore:220
Path: utzoo!attcan!uunet!cs.utexas.edu!rutgers!apple!bloom-beacon!mit-eddie!bbn!bbn.com!fkittred
From: fkittred@bbn.com (Fletcher Kittredge)
Newsgroups: comp.std.c,comp.sys.encore
Subject: Re: setjmp/longjmp
Keywords: setjmp, longjmp
Message-ID: <39197@bbn.COM>
Date: 27 Apr 89 18:04:03 GMT
References: <1447@cunixc.cc.columbia.edu> <12491@ut-emx.UUCP>
Sender: news@bbn.COM
Reply-To: fkittred@BBN.COM (Fletcher Kittredge)
Organization: Bolt Beranek and Newman Inc., Cambridge MA
Lines: 26

In article <12491@ut-emx.UUCP> clyde@ut-emx.UUCP (Clyde W. Hoover) writes:
>
>	Well, we ran headlong into that very problem ourselves.  What is
> going on is that the Encore C compiler puts variables into registers
> (making the 'register' declaration somewhat superflous).

This is common behavior for any optimizing compiler.  For instance,
the compilers for the RISC chips for Sun, HP and MIPS do this.  Compilers
can do a better job than humans in figuring out which variables should
be in registers.

>  Upon longjmp,
> the contents of the registers are restored to what they were at the time
> of the call to setjmp and since your flag has been stuffed into a register,
> it is being reset.

Again, this is standard behavior umong modern CPUs and Unix implementations.
I have found this behavior in DEC, HP and Sun systems.  Both document this
behavior, and it appears to me that ANSI C and Posix both require this
behavior.

regards,
fletcher


Fletcher E. Kittredge  fkittred@bbn.com