strcpy(pstring, function())

Now I have a function const char *get_string(size_t maxlen) where the significant part according to this problem is like

Code:

---

vector<char> str;
...
char *s = new char[str.size()+1];

/*        Copy the vector to passed string        */
for(size_t i = 0;  i < str.size();  i++)
        s[i] = str[i];
s[str.size()] = '\0';
str.clear();
return s;

---

in main() I have

Code:

---

char *s;
strcpy(s, get_string(4));
printf("\n%s", s);

---

There must be something wrong in the upper code 'cause if, in main(), I set s to NULL nothing seems to happen. What's going on?

Code:

---

char *s;
strcpy(s, get_string(4));
printf("\n%s", s);

---

This should give you a warning and a run-time error. You're trying to copy a string to unallocated memory. s is a pointer at this point, nothing more, so you need to point it to some memory before assigning to it.

-Prelude

>char *s;
>strcpy(s, get_string(4));
>printf("\n%s", s);

Should be:
s = get_string(4);

> s = strcpy(get_string(4));

No...

char * strcpy(char *dest, char *source);

And after the edit, still no.

You can't reassign strings like that.

Sorry about the editing. Since he didn't show the function heading, I didn't know the name of the function. And yes you can. Try it.

And of course I have tried passing s from main o get_string:

Code:

---

void get_string(char *s, size_t maxlen)
{
    ...
    if(s == NULL)
        s = new char[str.size()+1];

    /*        Copy the vector to passed string        */
    for(size_t i = 0;  i < str.size();  i++)
        s[i] = str[i];
    s[str.size()] = '\0';
    str.clear();
}

---

But it remains the same. And now s points to a local variable...

Code:

---

void get_string(char **s, size_t maxlen)
{
    ...
    if(*s == NULL)
        *s = new char[str.size()+1];

    /*        Copy the vector to passed string        */
    for(size_t i = 0;  i < str.size();  i++)
        (*s)[i] = str[i];
    (*s)[str.size()] = '\0';
    str.clear();
}

//And to call function, use something like:
char *s = NULL;
get_string(&s,80);

---

Ah! Could someone explain that code a bit? It works, alright but
char s[n];
getstr(s, m);
doesn't - not that it's a problem that is easily fixed with some polymorphzation but why.