> On Thu, Oct 29, 2020 at 04:50:54PM +0100, Jan Hubicka wrote:
> > * tree.c (build_string): Update.
> > * tree-core.h (tree_fixed_cst): Avoid typeless storage.
>
> Is it valid then to
> #define TREE_STRING_POINTER(NODE) \
> ((const char *)(STRING_CST_CHECK (NODE)->string.str))
> and strcpy etc. it around though?
> Maybe yes, because stores through char can alias anything.
Yep, I think it should be valid for that reason. The whole thing is not
terribly pretty (the wide-int change was better), but I do not know of
better solution and it affects our core datastructure. Typeless storage
is really complicated concept. Forutnately it seems that there are no
more hacks like this needed: both tree and gimple now gets non-zero
alias set.
Honza
>
> > diff --git a/gcc/tree-core.h b/gcc/tree-core.h
> > index c9280a8d3b1..63dbb5b8eab 100644
> > --- a/gcc/tree-core.h
> > +++ b/gcc/tree-core.h
> > @@ -1401,7 +1401,8 @@ struct GTY(()) tree_fixed_cst {
> > struct GTY(()) tree_string {
> > struct tree_typed typed;
> > int length;
> > - char str[1];
> > + /* Avoid char array that would make whole type to be typeless storage.
> > */
> > + struct {char c;} str[1];
> > };
> >
> > struct GTY(()) tree_complex {
> > diff --git a/gcc/tree.c b/gcc/tree.c
> > index 81f867ddded..84115630184 100644
> > --- a/gcc/tree.c
> > +++ b/gcc/tree.c
> > @@ -2273,7 +2273,7 @@ build_string (unsigned len, const char *str /*= NULL
> > */)
> > memcpy (s->string.str, str, len);
> > else
> > memset (s->string.str, 0, len);
> > - s->string.str[len] = '\0';
> > + s->string.str[len].c = '\0';
> >
> > return s;
> > }
>
> Jakub
>
