Re: [patch] Avoid #ifdef _GLIBCXX_DEBUG in regex_compiler.h

[Jonathan Wakely <jwakely at redhat dot com>]

We could go further and remove the ABI difference in regex_compiler
when using _GLIBCXX_DEBUG, as in the attached patch.

The trick is that for the char specialization we have padding bytes
between _M_is_non_matching (a bool) and _M_cache (a std::bitset), so
we can reuse one of those padding bytes for the _M_is_ready flag.

For the non-char specializations the _Dummy struct takes up one byte,
so we could reuse that for the _M_is_ready flag.

To be safe we should probably check that alignof(std::bitset<8> > 2)
so we know there really is a padding byte that can be re-used, and
place the _M_is_ready flag afterwards if there is no padding.

Attachment: regex_compiler.txt
Description: Text document