• State Not Answered
  • Locked Locked
  • Replies 13 replies
  • Subscribers 21 subscribers
  • Views 2221 views
  • Users 0 members are here
2025 survey

We are running a survey to help us improve the experience for all of our members. If you see the survey appear, please take the time to tell us about your experience if you can.

Options
Related
How was your experience today?
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

for(N = List->Head;N;N = N->Succ)

Mike Hwang 

struct NODE{
    struct NODE Succ;
    struct NODE Prev;
};

struct LIST{
    struct NODE *Head;
    struct NODE *Tail;
    int count;
};

struct LIST *List;
struct NODE *N;

......
for(N = List->Head;N;N = N->Succ)
{
    ......
}
Compiler C51 changed value of List->Head because of the side effect of N = N->Succ.What can I do?

Parents
  • 0 in reply to Bernhard Felkel

    "List is placed in XDATA because I use the large memory model"

    Ok, but shouldn't N therefore be placed in xdata as well? Quoting from your map file above:

    02000000H SYMBOL XDATA --- List
    00000001H SYMBOL DATA --- N

    "N is used in code: "N = List->Head" and "N = N->Succ" in the for-loop"

    Yes, I must have been sleeping. Again.

    I think Hans is right, the optimisation is legitimately causing this. The order of events is (pseudocode):

    List=An address;
    N=List->Head;
    LABEL:
    N=N->Succ;
    if(N) goto LABEL

    So, List and N can occupy the same location without anything going wrong.

    Stefan

Reply
  • 0 in reply to Bernhard Felkel

    "List is placed in XDATA because I use the large memory model"

    Ok, but shouldn't N therefore be placed in xdata as well? Quoting from your map file above:

    02000000H SYMBOL XDATA --- List
    00000001H SYMBOL DATA --- N

    "N is used in code: "N = List->Head" and "N = N->Succ" in the for-loop"

    Yes, I must have been sleeping. Again.

    I think Hans is right, the optimisation is legitimately causing this. The order of events is (pseudocode):

    List=An address;
    N=List->Head;
    LABEL:
    N=N->Succ;
    if(N) goto LABEL

    So, List and N can occupy the same location without anything going wrong.

    Stefan

Children
No data