Re: c/9266: decrement pointer side effects are not working properly

[Randy Fields <randy@fieldshome.com>]

The following reply was made to PR c/9266; it has been noted by GNATS.

>From randy@fieldshome.com  Mon Jan 13 00:52:34 2003
From: Randy Fields <randy@fieldshome.com>
To: bangerth@dealii.org,  gcc-bugs@gcc.gnu.org,  gcc-prs@gcc.gnu.org, 
 nobody@gcc.gnu.org,  randy@fieldshome.com,  gcc-gnats@gcc.gnu.org
Cc:  
Subject: Re: c/9266: decrement pointer side effects are not working properly
Date: Fri, 10 Jan 2003 14:57:53 -0700

 Greetings, and thank you for your quick response.  I see that depending 
 on the side effects of these types of statements (pointer decrement) is 
 not a good habit to be in, and will promptly change my own code so that 
 it works.  However, this same code base has been running (and compiling) 
 across many different platforms and compilers (MS VC++ 4,5,6,7, IRIX, 
 earlier versions of gcc) for six years.  This is the first time we have 
 encountered the problem.  I'm not saying that what the other compilers 
 are doing is correct, only that someone there may want to look more 
 closely at it for compatability sake.  I see several bugs on the list 
 that could potentially be caused by this very problem.  I'll be glad to 
 provide assembler code dumps, or any assistence that I can, if needed.
 
 Thanks,
 Randy Fields
 Artis LLC
 Research Programmer
 
 bangerth@dealii.org wrote:
 
 >Synopsis: decrement pointer side effects are not working properly
 >
 >State-Changed-From-To: open->closed
 >State-Changed-By: bangerth
 >State-Changed-When: Fri Jan 10 13:28:13 2003
 >State-Changed-Why:
 >    You're changing the same variable twice in the same statement,
 >    and the result depends on the order in which this happens.
 >    This invokes undefined behavior -- don't do this.
 >    
 >    W.
 >
 >http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=9266
 >
 >
 >  
 >