Thread: How to take care of malloc.c:2372 error

Code:

  if(cache[block].block == NULL){


  cache[block].block = (int*)malloc(blockSize * sizeof(int));


  }

This is the line that is having the error, but I am having a tough time figuring out how to allocate the memory correctly. I am trying to create a dynamic sized cache, based on user input and was told to put global variables in it even though I would have preferred not to. The majority of the code is below. It is a lot I know, I just don't know what I should be looking for.

Code:

#include<stdio.h>
#include<stdlib.h>


struct node
{
   int tag;
   int *block; //dynamic array
} *cache = NULL;


typedef struct node n;
int *mm = NULL;
int numLines, blockSize, cacheSize;


static void option1()
{
   int mmSize, i, tag;


   printf("Enter main memory size (words): ");
   scanf("%d", &mmSize);
   printf("Enter cache size (words): ");
   scanf("%d", &cacheSize);
   printf("Enter block size (words/blocks): ");
   scanf("%d", &blockSize);


   /*allocate space for MM and initialize*/


   mm = (int *)malloc(mmSize * sizeof(int));


   for (i = 0; i < mmSize; i++)
   {
       mm[i] = mmSize - 1;
   }


   numLines = cacheSize / blockSize;
   /*allocate space for cache and initialize*/
   cache = (n *)malloc(numLines * sizeof(n));


   for (i = 0; i < cacheSize; i++)
   {
       cache[i].tag = -1;
       cache[i].block = NULL;
   }
   tag = ((cacheSize/blockSize) - 1);
   return;
}


static void option2()
{
   int readOrWrite, mmAddress, writeValue, word, base, set, tag, block;


   printf("Enter 0 for read or 1 for write: ");
   scanf("%d", &readOrWrite);


   if (readOrWrite == 1)
   {


       printf("\nEnter main memory address to write to: ");
       scanf("%d", &mmAddress);
       printf("\nEnter value to write: ");
       scanf("%d", &writeValue);
   }


   else if (readOrWrite == 0)
   {
       printf("\nEnter main memory address to read from: ");
       scanf("%d", &mmAddress);
   }
   /*calculate tag, line of cache, and word associated w/ MM address*/
   printf("test1 \n");
   tag = mmAddress / cacheSize;
   block = 1;
   set = (mmAddress % cacheSize) / blockSize;
   word = mmAddress % blockSize;
   base = (mmAddress / blockSize) * blockSize;


   /*3 cases for hit/miss*/
   //CASE 1: MISS DUE TO UNALLOCATED BLOCK
   printf("test2 \n");
   if (cache[block].block == NULL)
   {
       cache[block].block = malloc(blockSize * sizeof(cache[block].block[0]));
   }
   //CASE 2: MISS DUE TO NON MATCHING TAGS
   if (cache[block].tag != tag)
   {
       cache[block].tag = tag;


       int i;


       for (i = 0; i < blockSize; i++)
       {
           cache[block].block[i] = mm[base + 1];
       }


       if (readOrWrite == 0)
       {
           printf("READ MISS!");
       }


       else if (readOrWrite == 1)
       {
           printf("WRITE MISS!");
           mm[mmAddress] = writeValue;
       }
   }
   //CASE 3: HIT IN THE CACHE, TAGS MATCH
   else if (cache[block].tag == tag)
   {
       if (readOrWrite == 0)
       {
           printf("YOU HAVE A READ HIT!");
           writeValue = cache[block].block[word];
       }


       else if (readOrWrite == 1)
       {
           printf("YOU HAVE A WRITE HIT!");
           cache[block].block[word] = writeValue;
           mm[mmAddress] = writeValue;
       }
   }
}


static void option4()
{
   int i;


   for (i = 0; i < numLines; i++)
   {
       if (cache[i].block != NULL)
       {
           free(cache[i].block);
       }


       if (cache != NULL)
       {
           free(cache);
       }
   }
}


int main()
{
   int option = 0;


   while (option != 4)
   {


       printf("\nCache memory allocation and mapping: \n");
       printf("------------------------------------\n");
       printf("1) Enter parameters \n");
       printf("2) Access cache \n");
       printf("3) Quit \n\n");
       scanf("%d", &option);


       switch (option)
       {


       case 1:
           option1();
           break;


       case 2:
           option2();
           break;


case3:
           option3();
           break;


       default:
           printf("\nOption not available, please try again. \n");
           break;
       }
   }
   return 0;
}

I’m using visual studio code, and while it does compile through, for some reason it halts when I try using the option 2 function and that’s where the malloc error happens. The error doesn’t show up on my gcc compiler, it just stops the program, but it did show up on an online compiler. I’m just not sure why this would happen. I only have the one program that is a .c so I don’t think it’s using the cpp compiler. I feel like I’m just allocating the memory for the cache wrong but then again I could be wrong about that too since I have no idea how to fix it.

When run on my gcc compiler, there is no error, but instead the program stops at the same spot where I was having problems before, but after running it on an online compiler I received a malloc.c:2372 error. You asked why I had global variables before, I don't want them and would prefer not to have them, but they were asked to be put in there that way. I am just not sure how to get this to work properly so that the cache is actually created so that I can see if it is a hit or a miss.