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.
+ /* Check alignment of the object. */
+ if (TREE_CODE (object) == COMPONENT_REF)
+ {
+ field = TREE_OPERAND (object, 1);
+ if (TREE_CODE (field) == FIELD_DECL && DECL_PACKED (field))
+ {
+ type_align = TYPE_ALIGN (type);
+ context = DECL_CONTEXT (field);
+ record_align = TYPE_ALIGN (context);
+ if ((record_align % type_align) != 0)
+ return context;
+ }
+ }
Why doesn't this recurse? What if you have a packed field three
COMPONENT_REFs down?
My patch works on
[hjl@gnu-cfl-1 pr51628-4]$ cat x.i
struct A { int i; } __attribute__ ((packed));
struct B { struct A a; };
struct C { struct B b; };
extern struct C *p;
int* g8 (void) { return &p->b.a.i; }
[hjl@gnu-cfl-1 pr51628-4]$ make x.s
/export/build/gnu/tools-build/gcc-debug/build-x86_64-linux/gcc/xgcc
-B/export/build/gnu/tools-build/gcc-debug/build-x86_64-linux/gcc/ -O2
-S x.i
x.i: In function ‘g8’:
x.i:7:25: warning: taking address of packed member of ‘struct A’ may
result in an unaligned pointer value [-Waddress-of-packed-member]
7 | int* g8 (void) { return &p->b.a.i; }
| ^~~~~~~~~
[hjl@gnu-cfl-1 pr51628-4]$
If it isn't what you had in mind, can you give me a testcase?
In that testcase, 'i' is the top COMPONENT_EXPR. What I was talking
about would be more like
struct A { int i; };
struct B { struct A a; };
struct C { struct B b __attribute__ ((packed)); };
extern struct C *p;
int* g8 (void) { return &p->b.a.i; }
Jason
