Use of freed memory

Using freed memory generates the following runtime errors:

• memory corruption (may cause an unpredictable failure in the future)
• random data read (when a heap block is re-used, other data can be in that location)

Depending on which error checks are enabled under Memory Errors in the configuration, the Memory Analysis tool can detect when free memory is read from or written to in the following conditions:

• Verify parameters in string and memory functions—when library functions read memory referred to by a pointer that's known to be free
• Enabled bounds checking (where possible)—when a newly allocated block contains altered data, meaning it was modified after it was previously deallocated

The notification for this type of memory error includes the following details:

• Severity: ERROR
• Description: data in freed memory block has been modified
• Pointer: address of the freed memory block
• Trap Function: one of: malloc calloc realloc free strcat strdup strncat strcmp strncmp strcpy strncpy strlen strchr strrchr index rindex strpbrk strspn strcspn strstr strtok memccpy memchr memmove memcpy memcmp memset bcopy bzero bcmp
• Alloc Kind: how memory was allocated for this block (malloc, calloc, or realloc)
• Location: source file and line of code where the error occurred (e.g., main.c:59)
• Count: number of blocks involved

The following code shows an example of using freed memory:

int main(int argc, char ** argv) {
  char * ptr = NULL;
  ptr = malloc(13);
  free(ptr);
  strcpy(ptr,"Hello World!");
  return 0;
}