Question

I am trying to wrap my head around C right now (mostly how pointers operate). I am trying to write this function described below:

/* EnterName enter a Name into a symbol table. Returns a
boolean indicating whether an entry for Name was
already listed in the table. Passes back an argument
containing an entry reference for the name.

Anyway, here is the code I have written and I am not sure how to test it at the moment. Wondering if someone could look over it and let me know if I am doing this right.

Thanks in advance.

Code::

bool EnterName(struct SymTab *ATable,
              const char *Name,
              struct SymEntry * *AnEntry)
{
              char name = *Name;
              unsigned hashval = hash (&name);
              struct SymEntry *ptr;

          ptr = ATable->Contents[hashval];

          while(ptr != NULL)
          {
                    if(strcmp(ptr->Name, &name)) 
                    {
                                 AnEntry = &ptr;
                                 return true;
                    } 
          }

          ptr = malloc(sizeof(struct SymEntry));
          ptr->Name = &name;
          AnEntry = &ptr;
          return false;

}

Answer 1

Does it run and produce the results you expect?

There’s no replacement for compiling code, running it with test data, comparing results to expected values, debugging, etc, when learning a new language. Showing untested code to others and asking if it’s OK isn’t the right approach.

Even the first two lines of the function don’t make sense:

   char name = *Name;
   unsigned hashval = hash(&name);

You’ve just taken the first character of Name into the name variable, and then try to hash its address.

Now, the loop:

          while(ptr != NULL)
          {
                    if(strcmp(ptr->Name, &name)) 
                    {
                                 AnEntry = &ptr;
                                 return true;
                    } 
          }

Doesn’t make sense either, since you’re not advancing ptr anywhere – it’s an infinite loop.

That said, there seems to be a step in the right direction in your code. You just have to get your types straight and fix all the rough corners. I suggest starting with small pieces – see that they compile and run, then proceed assembling into larger pieces.