On Fri, 26 Jan 2018, Jan Hubicka wrote:
> > 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.
Ah, ok. The patch is ok then. I suppose in theory complex pointers
or vector pointers would have the same issue if we'd ever generate
those (GIMPLE at least doens't like them ;)).
Richard.
> 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)
>
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
