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[51] simulation in KeilC question

shihwen chou

Hi, The test code is listed as below,

#pragma OT(0)
void main (void)
{
    DATA_MSG *b=NULL;
    DATA_MSG *a=NULL;

    b=(DATA_MSG *)malloc(sizeof(DATA_MSG));
    b->sMsgHeader.MessageType=E_Battery_Status;
    b->sMsgHeader.Extended=1;
    //Plug_Status=0;
    //Varible_Init();
    a=(DATA_MSG *)malloc(sizeof(DATA_MSG));
    a->sMsgHeader.MessageType=E_Get_Country_Info;
    a->sMsgHeader.Extended=0;
    if(b->sMsgHeader.Extended || a->sMsgHeader.Extended)
        EX3=1;
    else
        EX3=0;

I use the keil-C simulator to debug it. I found the pointer a and b point to the same memory location.
It means that the a overwrites b, I don't know why? Anyone knows it? Thanks a lot.

Parents
  • 0 in reply to shihwen chou

    Yes, that's it.

    Now you see that you have to define the size of the memory pool (aka "Heap") in advance.

    So it really doesn't help you - does it?

    You might just as well use the memory directly - and then you save the overheads!

    And you avoid all the other risks associated with Dynamic Allocation!

Reply
  • 0 in reply to shihwen chou

    Yes, that's it.

    Now you see that you have to define the size of the memory pool (aka "Heap") in advance.

    So it really doesn't help you - does it?

    You might just as well use the memory directly - and then you save the overheads!

    And you avoid all the other risks associated with Dynamic Allocation!

Children