Re: [PATCH] c++/modules: fix virtual destructors [PR103499]

[Nathaniel Shead <nathanieloshead@gmail.com>]

On Thu, Nov 09, 2023 at 05:57:39PM -0500, Nathan Sidwell wrote:
> On 11/9/23 04:55, Nathaniel Shead wrote:
> > I'm not sure if this is just papering over a general issue of clones not being
> > exported/imported, or if this is just an exception to the general case of
> > clones being able to be freely regenerated with no other issues.
> > 
> > Alternatively, would it be better to override the DECL_VINDEX of the original
> > declaration after filling it in for the clones as well? I wasn't able to see
> > anything depending on the current behaviour (though I didn't look very hard).
> 
> I think your patch is a fine approach. IIRC just streaming out the clones
> directly ran into a bunch of issues, hence the current implementation.
> 
> 
> ok
> 
> nathan

Sorry, I don't have write access, would you be able to push? Thanks.
(And for my other patch.)

> > 
> > Bootstrapped and regtexted on x86_64-pc-linux-gnu.
> > 
> > -- >8 --
> > 
> > Currently, cloned functions are not included in the CMI.  However, for
> > virtual destructors the clones must have a different DECL_VINDEX from
> > their base declaration: the former have an INTEGER_CST indicating the
> > index into the vtable, while the latter indicate the FUNCTION_DECL that
> > they're overriding.
> > 
> > As such, this patch ensures that DECL_VINDEX is properly passed on for
> > cloned functions as well to prevent this from causing issues.
> > 
> > 	PR c++/103499
> > 
> > gcc/cp/ChangeLog:
> > 
> > 	* module.cc (trees_out::decl_node): Write DECL_VINDEX for
> > 	virtual clones.
> > 	(trees_in::tree_node): Read DECL_VINDEX for virtual clones.
> > 
> > gcc/testsuite/ChangeLog:
> > 
> > 	* g++.dg/modules/pr103499_a.C: New test.
> > 	* g++.dg/modules/pr103499_b.C: New test.
> > 
> > Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
> > ---
> >   gcc/cp/module.cc                          |  6 ++++++
> >   gcc/testsuite/g++.dg/modules/pr103499_a.C | 12 ++++++++++++
> >   gcc/testsuite/g++.dg/modules/pr103499_b.C |  8 ++++++++
> >   3 files changed, 26 insertions(+)
> >   create mode 100644 gcc/testsuite/g++.dg/modules/pr103499_a.C
> >   create mode 100644 gcc/testsuite/g++.dg/modules/pr103499_b.C
> > 
> > diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
> > index c1c8c226bc1..416a7c414cc 100644
> > --- a/gcc/cp/module.cc
> > +++ b/gcc/cp/module.cc
> > @@ -8648,6 +8648,8 @@ trees_out::decl_node (tree decl, walk_kind ref)
> >         tree_node (target);
> >         tree_node (DECL_NAME (decl));
> > +      if (TREE_CODE (decl) == FUNCTION_DECL && DECL_VIRTUAL_P (decl))
> > +	tree_node (DECL_VINDEX (decl));
> >         int tag = insert (decl);
> >         if (streaming_p ())
> >   	dump (dumper::TREE)
> > @@ -9869,6 +9871,10 @@ trees_in::tree_node (bool is_use)
> >   		}
> >   	  }
> > +	/* A clone might have a different vtable entry.  */
> > +	if (res && TREE_CODE (res) == FUNCTION_DECL && DECL_VIRTUAL_P (res))
> > +	  DECL_VINDEX (res) = tree_node ();
> > +
> >   	if (!res)
> >   	  set_overrun ();
> >   	int tag = insert (res);
> > diff --git a/gcc/testsuite/g++.dg/modules/pr103499_a.C b/gcc/testsuite/g++.dg/modules/pr103499_a.C
> > new file mode 100644
> > index 00000000000..0497c2c5504
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/modules/pr103499_a.C
> > @@ -0,0 +1,12 @@
> > +// PR c++/103499
> > +// { dg-module-do compile }
> > +// { dg-additional-options "-fmodules-ts" }
> > +// { dg-module-cmi pr103499 }
> > +
> > +export module pr103499;
> > +
> > +export struct base {
> > +  virtual ~base() = default;
> > +};
> > +
> > +export struct derived : base {};
> > diff --git a/gcc/testsuite/g++.dg/modules/pr103499_b.C b/gcc/testsuite/g++.dg/modules/pr103499_b.C
> > new file mode 100644
> > index 00000000000..b7468562ba9
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/modules/pr103499_b.C
> > @@ -0,0 +1,8 @@
> > +// PR c++/103499
> > +// { dg-additional-options "-fmodules-ts" }
> > +
> > +import pr103499;
> > +
> > +void test(derived* p) {
> > +  delete p;
> > +}
> 
> -- 
> Nathan Sidwell
>