诡异的malloc

RT，这是个简单的代码处理数组插入，想在插入时判断此时数组是否将满，如果是就将数组扩大的原来的2倍。
不明白为什么int newspace=(int)malloc(size*sizet);有什么错误，如果把size改成一个定值就可以运行且结果正确，难道时malloc的bug?

#include <stdlib.h>//malloc
#include <string.h>//memset
#include <stdio.h>//printf
#define MAXIMUM 100
struct SeqList{
  int n;
  int * array;
  int max;
};

typedef struct SeqList *PSeqList;
PSeqList createSeqList(int size){
  PSeqList ptrSeqList=(PSeqList)malloc(sizeof(struct SeqList));
  if(ptrSeqList==NULL){
    return NULL;
  }
  
  ptrSeqList->n=0;
  ptrSeqList->array=(int*)malloc(size*sizeof(int));
  ptrSeqList->max=size;
  return ptrSeqList;
}

int insertElement(int pos, int val, PSeqList pSeqList){
  if(pSeqList==NULL)
    return -1;
  
  if(pSeqList->n==pSeqList->max){
    int size=pSeqList->n<<1;
    int sizet=sizeof(int);
    int *newspace=(int*)malloc(size*sizet);
    memset((void*)newspace,0,size*sizeof(int));
    int i=0;
    while(i++<pSeqList->max){
      newspace[i]=pSeqList->array[i];
    }
    free(pSeqList->array);
    pSeqList->array=newspace;
    pSeqList->max<<=1;
  }

  if(pSeqList->n==0){
    pSeqList->array[0]=val;
    pSeqList->n++;
    return 0;
  }

  int i;
  for(i=pSeqList->n;i>=pos;--i){
    pSeqList->array[i+1]=pSeqList->array[i];
  }
  pSeqList->n++;
  pSeqList->array[pos]=val;
}

void printArray(PSeqList ptrSeqList){
  printf("n: %d\n",ptrSeqList->n);
  printf("max: %d\n",ptrSeqList->max);
  int i=0;
  for(i;i<ptrSeqList->n;++i){
    printf("%d ",ptrSeqList->array[i]);
  }
}

int main(int argc, char*argv[]){
  PSeqList ptrSeqList=createSeqList(5);
  printArray(ptrSeqList);
  int i=0;
  for(i=0;i<10;++i){
    insertElement(i,i,ptrSeqList);
  }
  printArray(ptrSeqList);
  insertElement(5,110,ptrSeqList);
  printArray(ptrSeqList);
  return 0;
}