> On Thu, Feb 28, 2019 at 12:18 PM Jason Merrill <ja...@redhat.com> wrote:
> > On Thu, Feb 28, 2019 at 11:58 AM Jan Hubicka <hubi...@ucw.cz> wrote:
> > > sorry for late reply - I did not identify it as a patch to symbol table.
> > > Indeed we want can_refer_decl_in_current_unit_p is a good place to test
> > > this. Is there a reason to resrict this to functions with no body?
> >
> > If the function has a definition, then of course we can refer to it in
> > its own unit. Am I missing something?
>
> Ah, yes, I was. You mean, why do we care about DECL_INITIAL if
> DECL_EXTERNAL is set? I think I added that check out of caution.
>
> This would be a more straightforward change:
> commit 6af927c40585a4ff75a83b7cdabe8f9074a8d391
> Author: Jason Merrill <ja...@redhat.com>
> Date: Fri Jan 25 09:09:17 2019 -0500
>
> PR c++/80916 - spurious "static but not defined" warning.
>
> Nothing can refer to an internal decl with no definition, so we shouldn't
> treat such a decl as a possible devirtualization target.
>
> * gimple-fold.c (can_refer_decl_in_current_unit_p): Return false
> for an internal function with no definition.
Yes, this looks fine to me. Thanks a lot!
I hope frontends are not setting this combination of flags in scenarios
this transformation would be valid, but I can't think of a reason they
would be.
Patch is OK.
Honza
>
> diff --git a/gcc/gimple-fold.c b/gcc/gimple-fold.c
> index 7ef5004f5f9..62d2e0abc26 100644
> --- a/gcc/gimple-fold.c
> +++ b/gcc/gimple-fold.c
> @@ -121,9 +121,12 @@ can_refer_decl_in_current_unit_p (tree decl, tree
> from_decl)
> || !VAR_OR_FUNCTION_DECL_P (decl))
> return true;
>
> - /* Static objects can be referred only if they was not optimized out yet.
> */
> - if (!TREE_PUBLIC (decl) && !DECL_EXTERNAL (decl))
> + /* Static objects can be referred only if they are defined and not
> optimized
> + out yet. */
> + if (!TREE_PUBLIC (decl))
> {
> + if (DECL_EXTERNAL (decl))
> + return false;
> /* Before we start optimizing unreachable code we can be sure all
> static objects are defined. */
> if (symtab->function_flags_ready)
> diff --git a/gcc/testsuite/g++.dg/warn/unused-fn1.C
> b/gcc/testsuite/g++.dg/warn/unused-fn1.C
> new file mode 100644
> index 00000000000..aabc01b3f44
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/warn/unused-fn1.C
> @@ -0,0 +1,16 @@
> +// PR c++/80916
> +// { dg-options "-Os -Wunused" }
> +
> +struct j {
> + virtual void dispatch(void *) {}
> +};
> +template <typename>
> +struct i : j {
> + void dispatch(void *) {} // warning: 'void i< <template-parameter-1-1>
> >::dispatch(void*) [with <template-parameter-1-1> = {anonymous}::l]' declared
> 'static' but never defined [-Wunused-function]
> +};
> +namespace {
> + struct l : i<l> {};
> +}
> +void f(j *k) {
> + k->dispatch(0);
> +}
