Re: Memory question

[Allin Cottrell <cottrell wfu edu>]

On Wed, 28 Sep 2005, David Rosal wrote:

> Allin Cottrell wrote:
>
> > gchar *text = g_strdup_printf("banana %d", i);
> > gtk_entry_set_text(GTK_ENTRY(entry), text);
> > g_free(text);
>
> Is the above code really safe?

Yes!  A function such as gtk_entry_set_text() is bound to make a 
copy of the string offered by the caller.  Or at any rate it is 
bound _not_ to attempt to free that string.

Think about it: suppose you pass gtk_entry_set_text() a string 
literal:

gtk_entry_set_text(GTK_ENTRY(entry), "foo");

If gtk tried to free "foo" you'd get an immediate crash, since this 
is not storage obtained via malloc.  So we can infer that gtk (which 
is designed by wise and sane coders!) will not attempt to free 
strings that we pass into such functions.

So we can further infer that it is our business as callers of gtk 
functions to free strings that we pass to such functions, if we 
created these strings via functions that allocate storage -- i.e. 
that directly or indirectly call the C library function malloc() -- 
e.g. g_strdup(), g_strdup_printf() and friends.

Allin Cottrell