Re: c/10176: Broken nested Do loop: simple example. gcc 3.2 redhat

Re: c/10176: Broken nested Do loop: simple example. gcc 3.2 redhat

[bangerth]

Synopsis: Broken nested Do loop: simple example. gcc 3.2 redhat

State-Changed-From-To: open->feedback
State-Changed-By: bangerth
State-Changed-When: Fri Mar 21 01:51:28 2003
State-Changed-Why:
    Your program 4x.c is essentially equivalent to this one:
    --------------------------
    int main(void)
    {
      unsigned int count = 1;
      do {
        if( count % 3 ) { count *= 4; count += 2; }
        else            { count /= 3; }
        
        if( count == 1 ) break;
        if( count == 3 ) break;
      } while(1);
      return(0);
    }
    ----------------------
    What happens is that you never jump out of the inner loop.
    Unfortunately, I don't see right away why the loop should
    terminate at all. gcc seems to have the same problem, as
    does icc. Can you give a simple argument why it should?
    
    Thanks
      Wolfgang

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=10176

Re: c/10176: Broken nested Do loop: simple example. gcc 3.2 redhat

[bangerth]

Synopsis: Broken nested Do loop: simple example. gcc 3.2 redhat

State-Changed-From-To: feedback->closed
State-Changed-By: bangerth
State-Changed-When: Fri Mar 21 15:04:15 2003
State-Changed-Why:
    Mistaken

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=10176

c/10176: Broken nested Do loop: simple example. gcc 3.2 redhat

[ernstberg]

>Number:         10176
>Category:       c
>Synopsis:       Broken nested Do loop: simple example. gcc 3.2 redhat
>Confidential:   no
>Severity:       critical
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Mar 21 01:16:00 UTC 2003
>Closed-Date:
>Last-Modified:
>Originator:     ernstberg@bigvallet.net
>Release:        gcc 3.2
>Organization:
>Environment:
Redhat Linux 8.0
amd athlon 2400 dual cpu msi motherboard k7d master L
>Description:

 I am a hobby programmer and if I am missing some point forgive me:

 Simple nested do loops. One version with a set of values works.
 Change the values for a second version and the outer loop fails to execute.
Working values are if( x % 2 ){ x *= 3; x += 3;} else x /= 2;
 Broken values are if( x % 3 ){ x *= 4; x += 2;} else x /= 3;

Working program is 3x.c
Broken program is 4x.c
>How-To-Repeat:

 Compile and run.
>Fix:

 I don't know but I have seen the nested do loop broken in a ported C program that worked okay under Amiga's Sas C as well.
>Release-Note:
>Audit-Trail:
>Unformatted:
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