Re: checking status of GString

[Owen Taylor <otaylor redhat com>]

Federico Mena Quintero <federico@redhat.com> writes:

> >  [ Actually, assumming that NULL will have a bit-pattern of
> >    all zeros is not standard ANSI C, though it works
> >    universally on the platforms where GTK+ runs. ]
> 
> This is a runtime issue, not a compile-time issue.  The compiler must
> spit code to mangle zeros-in-pointers to whatever null pointer
> representation the machine uses.  Otherwise 
> 
> 	int i = 0;
> 	void *foo;
> 
> 	foo = i;
> 
> wouldn't work.  Whether it is good practice to use such code is a
> completely different issue :-)

But, only in assignments of integers to pointers. 
A compiler is allowed (at the penalty of breaking tons of code) to
write, for foo = i,

 if (i == 0)
   foo = SPECIAL_NULL_BIT_PATTERN;
 else
   /* skip the assignment */;

So, this is not the same case as:

  MyStruct *foo = g_new0 (MyStrict, 1);

  if (foo->pointer != NULL)
    g_free (foo->pointer);

Which isn't guaranteed to work. But does anyways on almost
any platform.

Anyways, enough language-lawyering for the day.

                                        Owen