Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!uunet!dino!hascall
From: hascall@cs.iastate.edu (John Hascall)
Newsgroups: comp.lang.c
Subject: Re: Compilers and programming style (was Re: A question of style)
Message-ID: <279@dino.cs.iastate.edu>
Date: 9 Jan 90 22:06:56 GMT
References: <1989Dec22.100135.2903@gdt.bath.ac.uk> <4367@rtech.rtech.com> <1989Dec31.153241.16479@gdt.bath.ac.uk> <649@codonics.COM> <1990Jan5.100042.26760@gdt.bath.ac.uk> <2283@dataio.Data-IO.COM> <534@bbxsda.UUCP>
Sender: usenet@dino.cs.iastate.edu
Organization: Iowa State Univ. Computation Center
Lines: 24

In article <534> scott@bbxsda.UUCP (Scott Amspoker) writes:
}In article <2283> bright@dataio.Data-IO.COM (Walter Bright) writes:

}>volatile int *p;
}>*p;		/* has side effects and must not be optimized away	*/
 
}Just curious - what kind of code should be generated for the above
}C fragment?

   (using VAX-11 as an example)

	  MOVL   @P,temp         ; move int pointed to by P into a throwaway
      or
          TSTL   @P              ; compare int pointed to by P to zero

   If you've never written a device driver, you may not understand why
   you would want to do this.  Some compilers will even `help' you out
   by `optimizing':

	  temp = *p;
      or
          if (*p);

John Hascall  /  ISU Comp Ctr