On Wed, 18 Jul 2018, Martin Sebor wrote:
> > > > + while (TREE_CODE (chartype) != INTEGER_TYPE)
> > > > + chartype = TREE_TYPE (chartype);
> > > This is a bit concerning. First under what conditions is chartype not
> > > going to be an INTEGER_TYPE? And under what conditions will extracting
> > > its type ultimately lead to something that is an INTEGER_TYPE?
> >
> > chartype is usually (maybe even always) pointer type here:
> >
> > const char a[] = "123";
> > extern int i;
> > n = strlen (&a[i]);
>
> But your hunch was correct that the loop isn't safe because
> the element type need not be an integer (I didn't know/forgot
> that the function is called for non-strings too). The loop
> should be replaced by:
>
> while (TREE_CODE (chartype) == ARRAY_TYPE
> || TREE_CODE (chartype) == POINTER_TYPE)
> chartype = TREE_TYPE (chartype);
As this function may be called "late" you need to cope with
the middle-end ignoring type changes and thus happily
passing int *** directly rather than (char *) of that.
Also doesn't the above yield int for int *[]?
I guess you really want
if (POINTER_TYPE_P (chartype))
chartype = TREE_TYPE (chartype);
while (TREE_CODE (chartype) == ARRAY_TYPE)
chartype = TREE_TYPE (chartype);
?
> if (TREE_CODE (chartype) != INTEGER_TYPE)
> return NULL;
>
> I will update the patch before committing.
>
> FWIW, it seems like it would be useful to extend the function to
> non-string arguments. That way it would be able to return array
> initializers in cases like this:
>
> const struct A { int a[2]; }
> a = { { 1, 2 } },
> b = { { 1, 2 } };
>
> int f (void)
> {
> return __builtin_memcmp (&a, &b, sizeof a);
> }
>
> which would in turn make it possible to fold the result of
> such calls analogously to strlen or strcmp.
>
> Martin
>
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
