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Re: New hashtable power 2 rehash policy
- From: Jonathan Wakely <jwakely at redhat dot com>
- To: François Dumont <frs dot dumont at gmail dot com>
- Cc: Daniel Krügler <daniel dot kruegler at gmail dot com>, "libstdc++ at gcc dot gnu dot org" <libstdc++ at gcc dot gnu dot org>, gcc-patches <gcc-patches at gcc dot gnu dot org>
- Date: Mon, 23 May 2016 12:31:32 +0100
- Subject: Re: New hashtable power 2 rehash policy
- Authentication-results: sourceware.org; auth=none
- References: <571B31E1 dot 6000101 at gmail dot com> <20160428102218 dot GI4241 at redhat dot com> <57374EB6 dot 80301 at gmail dot com> <CAGNvRgAE67QADfn_NQre=jwHebtfo4VxMEspxnBv+Zd9CV1vqw at mail dot gmail dot com> <573B7EF6 dot 7030203 at gmail dot com>
On 17/05/16 22:28 +0200, François Dumont wrote:
On 14/05/2016 19:06, Daniel Krügler wrote:
1) The function __clp2 is declared using _GLIBCXX14_CONSTEXPR, which
means that it is an inline function if and *only* if
_GLIBCXX14_CONSTEXPR really expands to constexpr, otherwise it is
*not* inline, which is probably not intended and could easily cause
ODR problems. I suggest to mark it unconditionally as inline,
regardless of _GLIBCXX14_CONSTEXPR.
Maybe _GLIBCXX14_CONSTEXPR should take inline value previous to C++14 mode.
That's probably a good idea.
For the moment I simply added the inline as done in other situations.
OK, thanks.
2) Furthermore I suggest to declare __clp2 as noexcept - this is
(intentionally) *not* implied by constexpr.
3) Is there any reason, why _Power2_rehash_policy::_M_next_bkt
shouldn't be noexcept?
4) Similar to (3) for _Power2_rehash_policy's member functions
_M_bkt_for_elements, _M_need_rehash, _M_state, _M_reset
For noexcept I throught we were only adding it if necessary. We might
have to go through a lot of code to find all places where noexcept
could be added. Jonathan will give his feedback.
I'm in favour of adding it anywhere that that definitely can't throw.
We don't *need* to do that everywhere, but it doesn't hurt.
For the moment I have added it on all those methods.
Great.
Thanks for feedback, updated and tested patch attached.
OK for trunk - thanks!