Re: C23 thoughts and opinions

On 24/05/2024 20:08, Chris M. Thomasson wrote:

On 5/24/2024 7:50 AM, David Brown wrote:

On 24/05/2024 01:05, Chris M. Thomasson wrote:

On 5/23/2024 6:35 AM, David Brown wrote:

On 22/05/2024 23:24, Chris M. Thomasson wrote:

On 5/22/2024 9:55 AM, David Brown wrote:

In an attempt to bring some topicality to the group, has anyone started using, or considering, C23 ?  There's quite a lot of change in it, especially compared to the minor changes in C17.

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Love the way std::vectors respect alignas... C++20, iirc?
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[...]

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I have no idea what you are talking about.

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std::vector actually respects alignas, on MSVC at least. I did not know this worked until I tried it. Iirc, Bonita was the one that sparked my test. It aligned itself on the proper boundaries. Very nice.
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But did you notice that this is c.l.c, not c.l.c++, and the topic is C23, not C++23 ?  Discussing comparisons or compatibility with C++ is fair enough, but talking about pure C++ matters (such as std::vector<>) is unlikely to be helpful.

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C has it as well... Very useful!

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I know C has alignas (now as a keyword in C23, instead of just _Alignas from C11).
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I know C++ has alignas (from C++11 onwards).
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What I don't understand is why you think std::vector<> "respects alignas" in C++20 - alignment for std::vector<> works like alignment for any other class in C++, and always has done.
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And what I /really/ don't understand is why you think it is remotely relevant here?  Even "alignas" in C is not particular relevant to this thread, except that it has become a keyword in C23 instead of a macro defined to _Alignas in <stdalign.h>.

 alignas is very nice because it can help me make a 100% portable version of some of my old exotic lock-free memory allocators that use rounding to get down to a header. Any point in the region can be rounded down to get at the header for the block. It involves aligning the main region on a large boundary, say 8192 bytes. This is a little trick for high performance lock-free allocators.

I know what "alignas" can do, and have made use of it.

 Iirc, I can make std::vector align its elements to say, L2 cachelines, and I can make std::vector align itself on a large boundary say 8192 bytes. All in std C++! That is nice.

I would be astounded to hear that std::vector could somehow disobey alignas specifiers.  I can appreciate that it could be useful to use alignas with std::vector's, but it is nothing special or dramatic.
And it has nothing to do with c.l.c., or with this thread.  Not have your allocators.
If you want to talk about your allocators, or good uses of alignas, start a new thread in c.l.c or c.l.c++, according to which is appropriate.  Both groups could do with new topical threads.  But if you want to be a positive contribution to these groups, please consider some basic rules - No links (to code sites or pointless videos), no out-of-the-blue topic changes, and no pantomime arguments with Bonita or olcott.
But stick to this thread if you want to talk about C23 and the changes it makes, whether you think they are good or bad.