Re: Fixing a sample from K&R book using cake static analyser

Kaz Kylheku <643-408-1753@kylheku.com> writes:

On Fri, 21 Jun 2024 09:45:21 -0300, Thiago Adams wrote:
>

Page 145, The C programming Language 2 Edition
 
/* install:  put (name, defn) in hashtab */
struct nlist *install(char *name, char *defn)
{
     struct nlist *np;
     unsigned hashval;
 
     if ((np = lookup(name)) == NULL) {  /* not found */
         np = (struct nlist *) malloc(sizeof(*np));
         if (np == NULL || (np->name = strdup(name)) == NULL)
             return NULL;
         hashval = hash(name);
         np->next = hashtab[hashval];
         hashtab[hashval] = np;
     } else      /* already there */
         free((void *) np->defn);  /* free previous defn */
 
     if ((np->defn = strdup(defn)) == NULL)
         return NULL;
     return np;
}

[snip attempts at tidying up...]

Watch and learn:
>
  struct nlist *install(char *name, char *defn)
  {
    struct nlist *existing = lookup(name);
>
    if (existing) {
      return existing;
    } else {
      struct nlist *np = calloc(1, sizeof (struct nlist));
      char *dupname = strdup(name);
      char *dupdefn = strdup(defn);
      unsigned hashval = hash(name);
>
      if (np && dupname && dupdefn) {
        np->name = dupname;
        np->defn = dupdefn;
        np->next = hashtab[hashval];
        hashtab[hashval] = np;
        return np;
      }
>
      free(dupdefn);
      free(dupname);
      free(np);
>
      return NULL;
    }
  }

You've over-simplified.  The function needs to replace the definition
with a strdup'd string (introduction another way to fail) when the name
is found by lookup.  It's just another nested if that's needed.  I don't
get why the goto crowd want to complicate it so much.

--
Ben.