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This compliant solution eliminates the NULL return and simply returns the item array, even if it is zero-length. The main function can effectively handle this situation without exhibiting erroneous behavior. Since the array lives on the stack, it must prevent returning a value in the stack frame (as mandated by DCL30-C. Declare objects with appropriate storage durations). So the getStack() function also takes a pointer to Inventory, so that it can return a pointer to its contents safely.

#include <stdio.h>

enum { INV_SIZE=20 };

typedef struct {
  size_t stockOfItem[INV_SIZE];
  size_t length;
} Inventory;

size_t *getStock(Inventory* iv);

int main(void) {
  Inventory iv;
  size_t i;
  size_t *item;

  iv.length = 0;
  
  /*
   * Other code that might modify the inventory but still
   * leave no items in it upon completion.
    */
  
  item = getStock(&iv);

  if (iv.length != 0) {
    printf("Stock of first item in inventory: %zd\n", item[0]);
  }
  
  return 0;
}

size_t *getStock(Inventory* iv) {
  return iv.stockOfItem->stockOfItem;
}

Noncompliant Code Example (Sentinel Value)

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Related Vulnerabilities

Search for vulnerabilities resulting from the violation of this guideline on the CERT website.

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