What is the meaning of this malloc error? Corrupted top size?

Question

I'm trying to initialize some values in couple of structs I created. (the goal of the program is to simulate virtual memory) For some reason when I try to initalize pgTable[i].validFlag = 1 I get this error:

malloc(): corrupted top size

but not if I initialize it to 0. I thought this had something to go with me going off the end of my array but I don't see how that's possible.

Can anyone tell me what I'm doing wrong?

  int* memmory = malloc( sizeof( int ) * sizeVM * pageSize );
  struct TLBentry* tlb = malloc( sizeof(struct TLBentry) * sizeTLB );
  struct pageTableEntry* pgTable = malloc( sizeof(struct pageTableEntry) * sizeVM );

  for( int i = 0; i < sizeTLB; i++){
    tlb[i].virtualAddress = i;
    tlb[i].physicalAddress = i;
  }

  for( int i = 0; i < sizePM; i++){
    pgTable[i].dirty = 0;
    pgTable[i].validFlag = 1;
    pgTable[i].physicalAddress = i;
  }

  memSys->virtMem = memmory;
  memSys->tlb = tlb;
  memSys->pgTable = pgTable;

Answer 1

Your loop goes up to sizePM while you allocate sizeVM entries.