[PATCH/expand] PR64011 Adjust bitsize when partial overflow happen for big-endian

[Jeff Law]

On 01/14/15 15:31, Jiong Wang wrote:
>
> agree, and I think the truncation is needed otherwise there may have ICE
> on some target.
>
> and I found current gcc LOCATION info is very good !
> have done an experimental hack on at "expand_assignment": 4931 where the
> tree is expanded,
> gcc could give quite useful & accurate warning based on tree LOCATION info.
>
> ./cc1 -O2 -mbig-endian pr48335-2.c
>
> pr48335-2.c: In function ‘f5’:
> pr48335-2.c:19:29: warning: overflow here !
>     ((U *)((char *) &s.d + 1))[3] = x;
>                               ^
>
> while we need to add warning at store_bit_field_using_insv where
> there is no accurate LOCATION info. but looks like it's acceptable?
>
> pr48335-2.c:19:33: warning: overflow here !
>     ((U *)((char *) &s.d + 1))[3] = x;
>                                   ^
Yes, I think we're on the right track now -- warn and truncate the the 
insertion.

I just scanned our set of warning flags to see if this would fit nicely 
under any of the existing flags, and it doesn't.  I guess putting it 
under -Wextra is probably best for now.

I think the warning text should indicate that the statement will write 
outside the bounds of the destination object or something along those lines.

Jeff