[Bug libstdc++/19495] basic_string::_M_rep() can produce an unnaturally aligned pointer to _Rep

["ncm-nospam at cantrip dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From ncm-nospam at cantrip dot org  2005-01-21 15:37 -------
Hmm, it's a little more complicated than I said, although it might be 
academic.  There's an implicit assumption in the code that any type 
on which basic_string<> might be instantiated has no stricter alignment
than _Rep itself.  But that's a different bug.  Probably the right way 
to fix it is to replace the first member of _Rep with an anonymous union:

  size_type               _M_length;

becomes

  union { size_type _M_length; _Some_big_aligned_type _M_alignment_dummy; };

I don't know if gcc supplies a built-in typedef for that.  Without
checking, I think tr1 must do.   I believe this can also be done
without breaking ABI on any actual target.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19495