> On Thu, 25 Jan 2018, Jan Hubicka wrote:
>
> > Hi,
> > the testcase triggers invalid warning on type mismatch because array
> > of pointers to complete type has different alias set from array of pointers
> > to incomplete type. This is valid, because incoplete pointer has alias set
> > of void_ptr which alias all pointers and arrays alias with their members.
>
> But isn't that a problem? Not if the pointer to incomlete type have
> alias set zero but IIRC they don't, right?
pointers to incomplete type are same as alias set of ptr_type_node (1 in this
case)
and pointer to complete types have different alias set but that set has
is_pointer flag. When checking for conflict we make 1 to alias with everything
that
has is_pointer flag in it, so it will return true for these two array types.
Honza
>
> Richard.
>
> > I already silenced the wanring for pointers but I forgot about arrays.
> >
> > Bootstrapped/regtested x86_64-linux, OK?
> >
> > * gcc.dg/lto/pr83954.h: New testcase.
> > * gcc.dg/lto/pr83954_0.c: New testcase.
> > * gcc.dg/lto/pr83954_1.c: New testcase.
> > * lto-symtab.c (warn_type_compatibility_p): Silence false positive
> > for type match warning on arrays of pointers.
> >
> > Index: testsuite/gcc.dg/lto/pr83954.h
> > ===================================================================
> > --- testsuite/gcc.dg/lto/pr83954.h (revision 0)
> > +++ testsuite/gcc.dg/lto/pr83954.h (working copy)
> > @@ -0,0 +1,3 @@
> > +struct foo;
> > +extern struct foo *FOO_PTR_ARR[1];
> > +
> > Index: testsuite/gcc.dg/lto/pr83954_0.c
> > ===================================================================
> > --- testsuite/gcc.dg/lto/pr83954_0.c (revision 0)
> > +++ testsuite/gcc.dg/lto/pr83954_0.c (working copy)
> > @@ -0,0 +1,8 @@
> > +/* { dg-lto-do link } */
> > +#include "pr83954.h"
> > +
> > +int main() {
> > + // just to prevent symbol removal
> > + FOO_PTR_ARR[1] = 0;
> > + return 0;
> > +}
> > Index: testsuite/gcc.dg/lto/pr83954_1.c
> > ===================================================================
> > --- testsuite/gcc.dg/lto/pr83954_1.c (revision 0)
> > +++ testsuite/gcc.dg/lto/pr83954_1.c (working copy)
> > @@ -0,0 +1,7 @@
> > +#include "pr83954.h"
> > +
> > +struct foo {
> > + int x;
> > +};
> > +struct foo *FOO_PTR_ARR[1] = { 0 };
> > +
> > Index: lto/lto-symtab.c
> > ===================================================================
> > --- lto/lto-symtab.c (revision 257009)
> > +++ lto/lto-symtab.c (working copy)
> > @@ -284,11 +284,22 @@ warn_type_compatibility_p (tree prevaili
> > alias_set_type set1 = get_alias_set (type);
> > alias_set_type set2 = get_alias_set (prevailing_type);
> >
> > - if (set1 && set2 && set1 != set2
> > - && (!POINTER_TYPE_P (type) || !POINTER_TYPE_P (prevailing_type)
> > + if (set1 && set2 && set1 != set2)
> > + {
> > + tree t1 = type, t2 = prevailing_type;
> > +
> > + /* Alias sets of arrays are the same as alias sets of the inner
> > + types. */
> > + while (TREE_CODE (t1) == ARRAY_TYPE && TREE_CODE (t2) == ARRAY_TYPE)
> > + {
> > + t1 = TREE_TYPE (t1);
> > + t2 = TREE_TYPE (t2);
> > + }
> > + if ((!POINTER_TYPE_P (t1) || !POINTER_TYPE_P (t2))
> > || (set1 != TYPE_ALIAS_SET (ptr_type_node)
> > - && set2 != TYPE_ALIAS_SET (ptr_type_node))))
> > - lev |= 5;
> > + && set2 != TYPE_ALIAS_SET (ptr_type_node)))
> > + lev |= 5;
> > + }
> > }
> >
> > return lev;
> >
> >
>
> --
> Richard Biener <rguent...@suse.de>
> SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
> 21284 (AG Nuernberg)
