http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51628
--- Comment #22 from rguenther at suse dot de <rguenther at suse dot de> 2013-04-03 09:20:21 UTC --- On Wed, 3 Apr 2013, ebotcazou at gcc dot gnu.org wrote: > > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51628 > > --- Comment #21 from Eric Botcazou <ebotcazou at gcc dot gnu.org> 2013-04-03 > 08:51:44 UTC --- > > One of the C frontend issues is that the type of the address of > > the field of the packed struct is int *, not int attribute((aligned(1))) > > *. And this is so because nothing adjusts the type of the FIELD_DECL > > to be a less aligned type. That is, we have > > > > <field_decl 0x7ffff6d245f0 i > > type <integer_type 0x7ffff6d175e8 int public SI > > size <integer_cst 0x7ffff6d1a0c0 constant 32> > > unit size <integer_cst 0x7ffff6d1a0e0 constant 4> > > align 32 symtab 0 alias set -1 canonical type 0x7ffff6d175e8 > > precision 32 min <integer_cst 0x7ffff6d1a060 -2147483648> max <integer_cst > > 0x7ffff6d1a080 2147483647> > > pointer_to_this <pointer_type 0x7ffff6d1f2a0>> > > packed SI file t.c line 2 col 9 size <integer_cst 0x7ffff6d1a0c0 32> > > unit size <integer_cst 0x7ffff6d1a0e0 4> > > align 8 offset_align 128 > > offset <integer_cst 0x7ffff6d02d80 type <integer_type 0x7ffff6d17000 > > sizetype> constant 0> > > bit offset <integer_cst 0x7ffff6d02e00 type <integer_type > > 0x7ffff6d170a8 bitsizetype> constant 0> context <record_type > > 0x7ffff6e1c3f0 Foo>> > > This is on x86, right? If the alignment of the field cannot be guaranteed to > be that of its type, then it should be made a bit-field. Maybe it's already > made a bit-field on strict-alignment targets. Note the FIELD_DECL is perfectly ok (align 8), it is its TREE_TYPE that is "bogus", and this type is used when building the pointer type used for taking the address of it (so you could argue _that_ is the bug - it shouldn't literally take TREE_TYPE of a FIELD_DECL when building the address of a COMPONENT_REF - the COMPONENT_REF surely only caring about the type of the value not the storage). Richard.
