[Bug c/52952] Wformat location info is bad (wrong column number)

["manu at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52952

--- Comment #7 from Manuel LÃpez-IbÃÃez <manu at gcc dot gnu.org> 2012-05-22 10:55:49 UTC ---
(In reply to comment #5)
> The format string could be even something like
>    void f() {
>          __builtin_printf(
>             u8R"abcd(%.)abcd"
>                "*d");
>                   }
> So, the question is, if we have a way to find from the source_location on the
> ADDR_EXPR around STRING_CST the original non-concatenated tokens, and given
> index into the (possibly) translated STRING_CST redo the lexing of those
> tokens, looking at which byte in the source tokens maps to that offset in the
> STRING_CST.

Is it possible to re-preprocess some tokens only? Do the line-maps keep track
of the locations of the tokens which make up a single string? If not, we would
need to create new source locations on-the-fly. Is this possible at all?