On Mon, Dec 17, 2018 at 1:43 PM H.J. Lu <hjl.to...@gmail.com> wrote: > > On Mon, Dec 17, 2018 at 1:39 AM Richard Biener > <richard.guent...@gmail.com> wrote: > > > > On Fri, Dec 14, 2018 at 11:48 PM H.J. Lu <hjl.to...@gmail.com> wrote: > > > > > > On Fri, Dec 14, 2018 at 2:10 PM Jason Merrill <ja...@redhat.com> wrote: > > > > > > > > On 12/13/18 6:56 PM, H.J. Lu wrote: > > > > > On Thu, Dec 13, 2018 at 12:50 PM Jason Merrill <ja...@redhat.com> > > > > > wrote: > > > > >> > > > > >> On 9/25/18 11:46 AM, H.J. Lu wrote: > > > > >>> On Fri, Aug 31, 2018 at 2:04 PM, Jason Merrill <ja...@redhat.com> > > > > >>> wrote: > > > > >>>> On 07/23/2018 05:24 PM, H.J. Lu wrote: > > > > >>>>> > > > > >>>>> On Mon, Jun 18, 2018 at 12:26 PM, Joseph Myers > > > > >>>>> <jos...@codesourcery.com> > > > > >>>>> wrote: > > > > >>>>>> > > > > >>>>>> On Mon, 18 Jun 2018, Jason Merrill wrote: > > > > >>>>>> > > > > >>>>>>> On Mon, Jun 18, 2018 at 11:59 AM, Joseph Myers > > > > >>>>>>> <jos...@codesourcery.com> > > > > >>>>>>> wrote: > > > > >>>>>>>> > > > > >>>>>>>> On Mon, 18 Jun 2018, Jason Merrill wrote: > > > > >>>>>>>> > > > > >>>>>>>>>> + if (TREE_CODE (rhs) == COND_EXPR) > > > > >>>>>>>>>> + { > > > > >>>>>>>>>> + /* Check the THEN path first. */ > > > > >>>>>>>>>> + tree op1 = TREE_OPERAND (rhs, 1); > > > > >>>>>>>>>> + context = check_address_of_packed_member (type, op1); > > > > >>>>>>>>> > > > > >>>>>>>>> > > > > >>>>>>>>> This should handle the GNU extension of re-using operand 0 if > > > > >>>>>>>>> operand > > > > >>>>>>>>> 1 is omitted. > > > > >>>>>>>> > > > > >>>>>>>> > > > > >>>>>>>> Doesn't that just use a SAVE_EXPR? > > > > >>>>>>> > > > > >>>>>>> > > > > >>>>>>> Hmm, I suppose it does, but many places in the compiler seem to > > > > >>>>>>> expect > > > > >>>>>>> that it produces a COND_EXPR with TREE_OPERAND 1 as NULL_TREE. > > > > >>>>>> > > > > >>>>>> > > > > >>>>>> Maybe that's used somewhere inside the C++ front end. For C a > > > > >>>>>> SAVE_EXPR > > > > >>>>>> is produced directly. > > > > >>>>> > > > > >>>>> > > > > >>>>> Here is the updated patch. Changes from the last one: > > > > >>>>> > > > > >>>>> 1. Handle COMPOUND_EXPR. > > > > >>>>> 2. Fixed typos in comments. > > > > >>>>> 3. Combined warn_for_pointer_of_packed_member and > > > > >>>>> warn_for_address_of_packed_member into > > > > >>>>> warn_for_address_or_pointer_of_packed_member. > > > > >>>> > > > > >>>> > > > > >>>>> c.i:4:33: warning: converting a packed ‘struct C *’ pointer > > > > >>>>> increases the > > > > >>>>> alignment of ‘long int *’ pointer from 1 to 8 > > > > >>>>> [-Waddress-of-packed-member] > > > > >>>> > > > > >>>> > > > > >>>> I think this would read better as > > > > >>>> > > > > >>>> c.i:4:33: warning: converting a packed ‘struct C *’ pointer > > > > >>>> (alignment 1) to > > > > >>>> ‘long int *’ (alignment 8) may result in an unaligned pointer value > > > > >>>> [-Waddress-of-packed-member] > > > > >>> > > > > >>> Fixed. > > > > >>> > > > > >>>>> + while (TREE_CODE (base) == ARRAY_REF) > > > > >>>>> + base = TREE_OPERAND (base, 0); > > > > >>>>> + if (TREE_CODE (base) != COMPONENT_REF) > > > > >>>>> + return NULL_TREE; > > > > >>>> > > > > >>>> > > > > >>>> Are you deliberately not handling the other handled_component_p > > > > >>>> cases? If > > > > >>>> so, there should be a comment. > > > > >>> > > > > >>> I changed it to > > > > >>> > > > > >>> while (handled_component_p (base)) > > > > >>> { > > > > >>> enum tree_code code = TREE_CODE (base); > > > > >>> if (code == COMPONENT_REF) > > > > >>> break; > > > > >>> switch (code) > > > > >>> { > > > > >>> case ARRAY_REF: > > > > >>> base = TREE_OPERAND (base, 0); > > > > >>> break; > > > > >>> default: > > > > >>> /* FIXME: Can it ever happen? */ > > > > >>> gcc_unreachable (); > > > > >>> break; > > > > >>> } > > > > >>> } > > > > >>> > > > > >>> Is there a testcase to trigger this ICE? I couldn't find one. > > > > >> > > > > >> You can take the address of an element of complex: > > > > >> > > > > >> __complex int i; > > > > >> int *p = &__real(i); > > > > >> > > > > >> You may get VIEW_CONVERT_EXPR with location wrappers. > > > > > > > > > > Fixed. I replaced gcc_unreachable with return NULL_TREE; > > > > > > > > Then we're back to my earlier question: are you deliberately not > > > > handling the other cases? Why not look through them as well? What if > > > > e.g. the operand of __real is a packed field? > > > > > > > > > > Here is the updated patch with > > > > > > diff --git a/gcc/c-family/c-warn.c b/gcc/c-family/c-warn.c > > > index 615134cfdac..f105742598e 100644 > > > --- a/gcc/c-family/c-warn.c > > > +++ b/gcc/c-family/c-warn.c > > > @@ -2669,6 +2669,9 @@ check_address_of_packed_member (tree type, tree rhs) > > > switch (code) > > > { > > > case ARRAY_REF: > > > + case REALPART_EXPR: > > > + case IMAGPART_EXPR: > > > + case VIEW_CONVERT_EXPR: > > > base = TREE_OPERAND (base, 0); > > > break; > > > default: > > > > don't we have handled_component_p () for this? (you're still > > missing BIT_FIELD_REF which might be used for vector > > element accesses) > > > > Do you have a testcase?
No, I suspect it might need some folding to trigger (IIRC I made the FEs use ARRAY_REFs but I'm not sure whether fully, esp. in the case of address-taking). My attempt: typedef int v4si __attribute__((vector_size(16))); struct X { v4si x; } __attribute__((packed)) x; int *foo() { return &x.x[1]; } that shows return &VIEW_CONVERT_EXPR<int[4]>(x.x)[1]; for both C and C++ (albeit checked GCC 8 here). Richard. > -- > H.J.